piRNAclusterDB 2.0: update and expansion of the piRNA cluster database.

PIWI-interacting RNAs (piRNAs) and their partnering PIWI proteins defend the animal germline against transposable elements and play a crucial role in fertility. Numerous studies in the past have uncovered many additional functions of the piRNA pathway, including gene regulation, anti-viral defense, and somatic transposon repression. Further, comparative analyses across phylogenetic groups showed that the PIWI/piRNA system evolves rapidly and exhibits great evolutionary plasticity. However, the presence of so-called piRNA clusters as the major source of piRNAs is common to nearly all metazoan species. These genomic piRNA-producing loci are highly divergent across taxa and critically influence piRNA populations in different evolutionary lineages. We launched the initial version of the piRNA cluster database to facilitate research on regulation and evolution of piRNA-producing loci across tissues und species. In recent years the amount of small RNA sequencing data that was generated and the abundance of species that were studied has grown rapidly. To keep up with this recent progress, we have released a major update for the piRNA cluster database (https://www.smallrnagroup.uni-mainz.de/piRNAclusterDB), expanding it from 12 to a total of 51 species with hundreds of new datasets, and revised its overall structure to enable easy navigation through this large amount of data.

Protein speciation is likely to increase the chance of proteins to be determined in 2-DE/MS.

Multiple spotting due to protein speciation might increase a protein's chance of being captured in a random selection of 2-DE spots. We tested this expectation in new (PXD015649) and previously published 2-DE/MS data of porcine and human tissues. For comparison, we included bottom-up proteomics studies (BU-LC/MS) of corresponding biological materials. Analyses of altogether ten datasets proposed that amino acid modification fosters multispotting in 2-DE. Thus, the number of 2-DE spots containing a particular protein more tightly associated with a peptide diversity measure accounting for amino acid modification than with an alternative one disregarding it. Furthermore, every 11th amino acid was a post-translational modification candidate site in 2-DE/MS proteins, whereas in BU-LC/MS proteins this was merely the case in every 21st amino acid. Alternative splicing might contribute to multispotting, since genes encoding 2-DE/MS proteins were found to have on average about 0.3 more transcript variants than their counterparts from BU-LC/MS studies. Correspondingly, resolution completeness as estimated from the representation of transcript variant-rich genes was higher in 2-DE/MS than BU-LC/MS datasets. These findings suggest that the ability to resolve proteomes down to protein species can lead to enrichment of multispotting proteins in 2-DE/MS. Low sensitivity of stains and MS instruments appears to enhance this effect.

Genomics and transcriptomics of epizoic Seisonidea (Rotifera, syn. Syndermata) reveal strain formation and gradual gene loss with growing ties to the host.

BACKGROUND: Seisonidea (also Seisonacea or Seisonidae) is a group of small animals living on marine crustaceans (Nebalia spec.) with only four species described so far. Its monophyletic origin with mostly free-living wheel animals (Monogononta, Bdelloidea) and endoparasitic thorny-headed worms (Acanthocephala) is widely accepted. However, the phylogenetic relationships inside the Rotifera-Acanthocephala clade (Rotifera sensu lato or Syndermata) are subject to ongoing debate, with consequences for our understanding of how genomes and lifestyles might have evolved. To gain new insights, we analyzed first drafts of the genome and transcriptome of the key taxon Seisonidea. RESULTS: Analyses of gDNA-Seq and mRNA-Seq data uncovered two genetically distinct lineages in Seison nebaliae Grube, 1861 off the French Channel coast. Their mitochondrial haplotypes shared only 82% sequence identity despite identical gene order. In the nuclear genome, distinct linages were reflected in different gene compactness, GC content and codon usage. The haploid nuclear genome spans ca. 46 Mb, of which 96% were reconstructed. According to ~ 23,000 SuperTranscripts, gene number in S. nebaliae should be within the range published for other members of Rotifera-Acanthocephala. Consistent with this, numbers of metazoan core orthologues and ANTP-type transcriptional regulatory genes in the S. nebaliae genome assembly were between the corresponding numbers in the other assemblies analyzed. We additionally provide evidence that a basal branching of Seisonidea within Rotifera-Acanthocephala could reflect attraction to the outgroup. Accordingly, rooting via a reconstructed ancestral sequence led to monophyletic Pararotatoria (Seisonidea+Acanthocephala) within Hemirotifera (Bdelloidea+Pararotatoria). CONCLUSION: Matching genome/transcriptome metrics with the above phylogenetic hypothesis suggests that a haploid nuclear genome of about 50 Mb represents the plesiomorphic state for Rotifera-Acanthocephala. Smaller genome size in S. nebaliae probably results from subsequent reduction. In contrast, genome size should have increased independently in monogononts as well as bdelloid and acanthocephalan stem lines. The present data additionally indicate a decrease in gene repertoire from free-living to epizoic and endoparasitic lifestyles. Potentially, this reflects corresponding steps from the root of Rotifera-Acanthocephala via the last common ancestors of Hemirotifera and Pararotatoria to the one of Acanthocephala. Lastly, rooting via a reconstructed ancestral sequence may prove useful in phylogenetic analyses of other deep splits.

Intra-Protein Coevolution Is Increasingly Functional with Greater Proximity to Fertilization.

Intramolecular coevolution of amino acid sites has repeatedly been studied to improve predictions on protein structure and function. Thereby, the focus was on bacterial proteins with available crystallographic data. However, intramolecular coevolution has not yet been compared between protein sets along a gradient of functional proximity to fertilization. This is especially true for the potential effect of external selective forces on intraprotein coevolution. In this study, we investigated both aspects in equally sized sets of mammalian proteins representing spermatozoa, testis, entire body, and liver. For coevolutionary analyses, we derived the proportion of covarying sites per protein from amino acid alignments of 10 mammalian orthologues each. In confirmation of the validity of our coevolution proxy, we found positive associations with the nonsynonymous or amino acid substitution rate in all protein sets. However, our coevolution proxy negatively correlated with the number of protein interactants (node degree) in male reproductive protein sets alone. In addition, a negative association of our coevolution proxy with protein hydrophobicity was significant in sperm proteins only. Accordingly, the restrictive effect of protein interactants was most pronounced in male reproductive proteins, and the tendency of sperm proteins to form internal structures decreased the more coevolutionary sites they had. Both aspects illustrate that the share of outward and thus functional coevolution increases with greater proximity to fertilization. We found this conclusion confirmed by additional comparisons within sperm proteins. Thus, sperm proteins with high hydrophobicity had the lowest proportions of covarying sites and, according to gene annotations, localized more frequently to internal cellular structures. They should therefore be less exposed to postcopulatory forms of sexual selection. Their counterparts with low hydrophobicity had larger proportions of covarying sites and more often resided at the cell membrane or were secreted. At the cellular level, they are thus closer to externally induced forces of postcopulatory selection which are known for their potential to increase substitution rates. In addition, we show that the intermediary status of the testicular protein set in correlation analyses is probably due to a special combination of reproductive and somatic involvements.

Fertility Relevance Probability Analysis Shortlists Genetic Markers for Male Fertility Impairment.

Impairment of male fertility is one of the major public health issues worldwide. Nevertheless, genetic causes of male sub- and infertility can often only be suspected due to the lack of reliable and easy-to-use routine tests. Yet, the development of a marker panel is complicated by the large quantity of potentially predictive markers. Actually, hundreds or even thousands of genes could have fertility relevance. Thus, a systematic method enabling a selection of the most predictive markers out of the many candidates is required. As a criterion for marker selection, we derived a gene-specific score, which we refer to as fertility relevance probability (FRP). For this purpose, we first categorized 2,753 testis-expressed genes as either candidate markers or non-candidates, according to phenotypes in male knockout mice. In a parallel approach, 2,502 genes were classified as candidate markers or non-candidates based on phenotypes in men. Subsequently, we conducted logistic regression analyses with evolutionary rates of genes (dN/dS), transcription levels in testis relative to other organs, and connectivity of the encoded proteins in a protein-protein interaction network as covariates. In confirmation of the procedure, FRP values showed the expected pattern, thus being overall higher in genes with known relevance for fertility than in their counterparts without corresponding evidence. In addition, higher FRP values corresponded with an increased dysregulation of protein abundance in spermatozoa of 37 men with normal and 38 men with impaired fertility. Present analyses resulted in a ranking of genes according to their probable predictive power as candidate markers for male fertility impairment. Thus, AKAP4, TNP1, DAZL, BRDT, DMRT1, SPO11, ZPBP, HORMAD1, and SMC1B are prime candidates toward a marker panel for male fertility impairment. Additional candidate markers are DDX4, SHCBP1L, CCDC155, ODF1, DMRTB1, ASZ1, BOLL, FKBP6, SLC25A31, PRSS21, and RNF17. FRP inference additionally provides clues for potential new markers, thereunder TEX37 and POU4F2. The results of our logistic regression analyses are freely available at the PreFer Genes website (https://prefer-genes.uni-mainz.de/).

Temperature-responsive miRNAs in Drosophila orchestrate adaptation to different ambient temperatures.

The majority of Drosophila genes are expressed in a temperature-dependent manner, but the way in which small RNAs may contribute to this effect is completely unknown as we currently lack an idea of how small RNA transcriptomes change as a function of temperature. Applying high-throughput sequencing techniques complemented by quantitative real-time PCR experiments, we demonstrate that altered ambient temperature induces drastic but reversible changes in sequence composition and total abundance of both miRNA and piRNA populations. Further, mRNA sequencing reveals that the expression of miRNAs and their predicted target transcripts correlates inversely, suggesting that temperature-responsive miRNAs drive adaptation to different ambient temperatures on the transcriptome level. Finally, we demonstrate that shifts in temperature affect both primary and secondary piRNA pools, and the observed aberrations are consistent with altered expression levels of the involved Piwi-pathway factors. We further reason that enhanced ping-pong processing at 29°C is driven by dissolved RNA secondary structures at higher temperatures, uncovering target sites that are not accessible at low temperatures. Together, our results show that small RNAs are an important part of epigenetic regulatory mechanisms that ensure homeostasis and adaptation under fluctuating environmental conditions.

Tupaia small RNAs provide insights into function and evolution of RNAi-based transposon defense in mammals.

Argonaute proteins comprising Piwi-like and Argonaute-like proteins and their guiding small RNAs combat mobile DNA on the transcriptional and post-transcriptional level. While Piwi-like proteins and associated piRNAs are generally restricted to the germline, Argonaute-like proteins and siRNAs have been linked with transposon control in the germline as well as in the soma. Intriguingly, evolution has realized distinct Argonaute subfunctionalization patterns in different species but our knowledge about mammalian RNA interference pathways relies mainly on findings from the mouse model. However, mice differ from other mammals by absence of functional Piwil3 and expression of an oocyte-specific Dicer isoform. Thus, studies beyond the mouse model are required for a thorough understanding of function and evolution of mammalian RNA interference pathways. We high-throughput sequenced small RNAs from the male Tupaia belangeri germline, which represents a close outgroup to primates, hence phylogenetically links mice with humans. We identified transposon-derived piRNAs as well as siRNAs clearly contrasting the separation of piRNA- and siRNA-pathways into male and female germline as seen in mice. Genome-wide analysis of tree shrew transposons reveal that putative siRNAs map to transposon sites that form foldback secondary structures thus representing suitable Dicer substrates. In contrast piRNAs target transposon sites that remain accessible. With this we provide a basic mechanistic explanation how secondary structure of transposon transcripts influences piRNA- and siRNA-pathway utilization. Finally, our analyses of tree shrew piRNA clusters indicate A-Myb and the testis-expressed transcription factor RFX4 to be involved in the transcriptional regulation of mammalian piRNA clusters.

DSB profiles in human spermatozoa highlight the role of TMEJ in the male germline.

The male mammalian germline is characterized by substantial chromatin remodeling associated with the transition from histones to protamines during spermatogenesis, followed by the reversal to nucleohistones in the male pronucleus preceding the zygotic genome activation. Both transitions are associated with the extensive formation of DNA double-strand breaks (DSBs), requiring an estimated 5 to 10 million transient DSBs per spermatozoa. Additionally, the high transcription rate in early stages of spermatogenesis leads to transcription-coupled damage preceding meiotic homologous recombination, potentially further contributing to the DSB landscape in mature spermatozoa. Once meiosis is completed, spermatozoa remain haploid and therefore cannot rely on error-free homologous recombination, but instead depend on error-prone classical non-homologous end joining (cNHEJ). This DNA damage/repair-scenario is proposed to be one of the main causes of the observed paternal mutation propensity in human evolution. Recent studies have shown that DSBs in the male pronucleus are repaired by maternally provided Polθ in Caenorhabditis elegans through Polθ-mediated end joining (TMEJ). Additionally, population genetic datasets have revealed a preponderance of TMEJ signatures associated with human variation. Since these signatures are the result of the combined effect of TMEJ and DSB formation in spermatozoa and male pronuclei, we used a BLISS-based protocol to analyze recurrent DSBs in mature human sperm heads as a proxy of the male pronucleus before zygotic chromatin remodeling. The DSBs were found to be enriched in (YR)n short tandem repeats and in evolutionarily young SINEs, reminiscent to patterns observed in murine spermatids, indicating evolutionary hotspots of recurrent DSB formation in mammalian spermatozoa. Additionally, we detected a similar DSB pattern in diploid human IMR90 cells when cNHEJ was selectively inhibited, indicating the significant impact of absent cNHEJ on the sperm DSB landscape. Strikingly, regions associated with most retained histones, and therefore less condensed chromatin, were not strongly enriched with recurrent DSBs. In contrast, the fraction of retained H3K27me3 in the mature spermatozoa displayed a strong association with recurrent DSBs. DSBs in H3K27me3 are associated with a preference for TMEJ over cNHEJ during repair. We hypothesize that the retained H3K27me3 may trigger transgenerational DNA repair by priming maternal Polθ to these regions.

Evolutionary conservation of mammalian sperm proteins associates with overall, not tyrosine, phosphorylation in human spermatozoa.

We investigated possible associations between sequence evolution of mammalian sperm proteins and their phosphorylation status in humans. As a reference, spermatozoa from three normozoospermic men were analyzed combining two-dimensional gel electrophoresis, immunoblotting, and mass spectrometry. We identified 99 sperm proteins (thereof 42 newly described) and determined the phosphorylation status for most of them. Sequence evolution was studied across six mammalian species using nonsynonymous/synonymous rate ratios (dN/dS) and amino acid distances. Site-specific purifying selection was assessed employing average ratios of evolutionary rates at phosphorylated versus nonphosphorylated amino acids (α). According to our data, mammalian sperm proteins do not show statistically significant sequence conservation difference, no matter if the human ortholog is a phosphoprotein with or without tyrosine (Y) phosphorylation. In contrast, overall phosphorylation of human sperm proteins, i.e., phosphorylation at serine (S), threonine (T), and/or Y residues, associates with above-average conservation of sequences. Complementary investigations suggest that numerous protein-protein interactants constrain sequence evolution of sperm phosphoproteins. Although our findings reject a special relevance of Y phosphorylation for sperm functioning, they still indicate that overall phosphorylation substantially contributes to proper functioning of sperm proteins. Hence, phosphorylated sperm proteins might be considered as prime candidates for diagnosis and treatment of reduced male fertility.

R-loop landscape in mature human sperm: Regulatory and evolutionary implications.

R-loops are three-stranded nucleic acid structures consisting of an RNA:DNA hybrid and a displaced DNA strand. While R-loops pose a potential threat to genome integrity, they constitute 5% of the human genome. The role of R-loops in transcriptional regulation, DNA replication, and chromatin signature is becoming increasingly clear. R-loops are associated with various histone modifications, suggesting that they may modulate chromatin accessibility. To potentially harness transcription-coupled repair mechanisms in the germline, nearly the entire genome is expressed during the early stages of male gametogenesis in mammals, providing ample opportunity for the formation of a transcriptome-dependent R-loop landscape in male germ cells. In this study, our data demonstrated the presence of R-loops in fully mature human and bonobo sperm heads and their partial correspondence to transcribed regions and chromatin structure, which is massively reorganized from mainly histone to mainly protamine-packed chromatin in mature sperm. The sperm R-loop landscape resembles characteristic patterns of somatic cells. Surprisingly, we detected R-loops in both residual histone and protamine-packed chromatin and localize them to still-active retroposons, ALUs and SINE-VNTR-ALUs (SVAs), the latter has recently arisen in hominoid primates. We detected both evolutionarily conserved and species-specific localizations. Comparing our DNA-RNA immunoprecipitation (DRIP) data with published DNA methylation and histone chromatin immunoprecipitation (ChIP) data, we hypothesize that R-loops epigenetically reduce methylation of SVAs. Strikingly, we observe a strong influence of R-loops on the transcriptomes of zygotes from early developmental stages before zygotic genome activation. Overall, these findings suggest that chromatin accessibility influenced by R-loops may represent a system of inherited gene regulation.

Human sperm heads harbor modified YsRNA as transgenerationally inherited non-coding RNAs.

Most epigenetic information is reprogrammed during gametogenesis and early development. However, some epigenetic information persists and can be inherited, a phenomenon that is common in plants. On the other hand, there are increasing examples of epigenetic inheritance in metazoans, especially for small non-coding RNAs. The presence of regulatory important RNAs in oocytes is undisputed, whereas the corresponding RNA payload in spermatozoa and its regulatory influence in the zygote and early embryogenesis is largely enigmatic. For humans, we herein describe small YRNA fragments (YsRNA) as a paternal contribution to the zygote. First, we trace the biogenesis of these YsRNAs from the source YRNAs with respect to the 5' and 3' modifications. Both the length and modifications make these YsRNAs reminiscent of canonical piRNAs that are not derived from piRNA clusters. Second, from the early stages of spermatogenesis to maturation in the epididymis, we observe distinct YsRNA profile dynamics in the male germline. We detected YsRNAs exclusively in mature sperm heads, the precursor of the male pronucleus in the zygote, suggesting an important role of the epididymis as a site for transmitting and modification of epigenetic information in the form of YsRNA between soma and germline in humans. Since this YsRNA-based epigenetic mechanism is effective across generations, we wondered whether this phenomenon of epigenetic inheritance has an adaptive value. Full-length YRNAs bind to Ro60, an RNA chaperone that additionally binds to non-coding RNAs. We described the profiles of non-coding RNAs bound to Ro60 in the human sperm head and detected specific binding profiles of RNA to Ro60 but no YRNA bound to Ro60. We hypothesize that the sperm head Ro60 system is functional. An adaptive phenotype mediated by the presence of a large amount of YsRNA in the sperm head, and thus as a paternal contribution in the zygote, might be related to an association of YsRNA with YRNA that prevents the adoption of a YRNA secondary structure capable of binding to Ro60. We hypothesize that preventing YRNAs from acting as Ro60-associated gatekeepers for misfolded RNAs in the zygote and early development may enhance RNA chaperoning and, thus, represent the adaptive molecular phenotype.

Generation of somatic de novo structural variation as a hallmark of cellular senescence in human lung fibroblasts.

Cellular senescence is characterized by replication arrest in response to stress stimuli. Senescent cells accumulate in aging tissues and can trigger organ-specific and possibly systemic dysfunction. Although senescent cell populations are heterogeneous, a key feature is that they exhibit epigenetic changes. Epigenetic changes such as loss of repressive constitutive heterochromatin could lead to subsequent LINE-1 derepression, a phenomenon often described in the context of senescence or somatic evolution. LINE-1 elements decode the retroposition machinery and reverse transcription generates cDNA from autonomous and non-autonomous TEs that can potentially reintegrate into genomes and cause structural variants. Another feature of cellular senescence is mitochondrial dysfunction caused by mitochondrial damage. In combination with impaired mitophagy, which is characteristic of senescent cells, this could lead to cytosolic mtDNA accumulation and, as a genomic consequence, integrations of mtDNA into nuclear DNA (nDNA), resulting in mitochondrial pseudogenes called numts. Thus, both phenomena could cause structural variants in aging genomes that go beyond epigenetic changes. We therefore compared proliferating and senescent IMR-90 cells in terms of somatic de novo numts and integrations of a non-autonomous composite retrotransposons - the so-called SVA elements-that hijack the retropositional machinery of LINE-1. We applied a subtractive and kinetic enrichment technique using proliferating cell DNA as a driver and senescent genomes as a tester for the detection of nuclear flanks of de novo SVA integrations. Coupled with deep sequencing we obtained a genomic readout for SVA retrotransposition possibly linked to cellular senescence in the IMR-90 model. Furthermore, we compared the genomes of proliferative and senescent IMR-90 cells by deep sequencing or after enrichment of nuclear DNA using AluScan technology. A total of 1,695 de novo SVA integrations were detected in senescent IMR-90 cells, of which 333 were unique. Moreover, we identified a total of 81 de novo numts with perfect identity to both mtDNA and nuclear hg38 flanks. In summary, we present evidence for possible age-dependent structural genomic changes by paralogization that go beyond epigenetic modifications. We hypothesize, that the structural variants we observe potentially impact processes associated with replicative aging of IMR-90 cells.

RDA coupled with deep sequencing detects somatic SVA-retrotranspositions and mosaicism in the human brain.

Cells of the developing human brain are affected by the progressive acquisition of genetic and epigenetic alterations that have been reported to contribute to somatic mosaicism in the adult brain and are increasingly considered a possible cause of neurogenetic disorders. A recent work uncovered that the copy-paste transposable element (TE) LINE-1 (L1) is mobilized during brain development, and thus mobile non-autonomous TEs like AluY and SINE-VNTR-Alu (SVA) families can use L1 activity in trans, leading to de novo insertions that may influence the variability of neural cells at genetic and epigenetic levels. In contrast to SNPs and when considering substitutional sequence evolution, the presence or absence of TEs at orthologous loci represents highly informative clade markers that provide insights into the lineage relationships between neural cells and how the nervous system evolves in health and disease. SVAs, as the 'youngest' class of hominoid-specific retrotransposons preferentially found in gene- and GC-rich regions, are thought to differentially co-regulate nearby genes and exhibit a high mobility in the human germline. Therefore, we determined whether this is reflected in the somatic brain and used a subtractive and kinetic enrichment technique called representational difference analysis (RDA) coupled with deep sequencing to compare different brain regions with respect to de novo SINE-VNTR-Alu insertion patterns. As a result, we detected somatic de novo SVA integrations in all human brain regions analyzed, and the majority of de novo insertions can be attributed to lineages of telencephalon and metencephalon, since most of the examined integrations are unique to different brain regions under scrutiny. The SVA positions were used as presence/absence markers, forming informative sites that allowed us to create a maximum parsimony phylogeny of brain regions. Our results largely recapitulated the generally accepted evo-devo patterns and revealed chromosome-wide rates of de novo SVA reintegration targets and preferences for specific genomic regions, e.g., GC- and TE-rich regions as well as close proximity to genes that tend to fall into neural-specific Gene Ontology pathways. We concluded that de novo SVA insertions occur in the germline and somatic brain cells at similar target regions, suggesting that similar retrotransposition modes are effective in the germline and soma.

proTRAC--a software for probabilistic piRNA cluster detection, visualization and analysis.

BACKGROUND: Throughout the metazoan lineage, typically gonadal expressed Piwi proteins and their guiding piRNAs (~26-32nt in length) form a protective mechanism of RNA interference directed against the propagation of transposable elements (TEs). Most piRNAs are generated from genomic piRNA clusters. Annotation of experimentally obtained piRNAs from small RNA/cDNA-libraries and detection of genomic piRNA clusters are crucial for a thorough understanding of the still enigmatic piRNA pathway, especially in an evolutionary context. Currently, detection of piRNA clusters relies on bioinformatics rather than detection and sequencing of primary piRNA cluster transcripts and the stringency of the methods applied in different studies differs considerably. Additionally, not all important piRNA cluster characteristics were taken into account during bioinformatic processing. Depending on the applied method this can lead to: i) an accidentally underrepresentation of TE related piRNAs, ii) overlook duplicated clusters harboring few or no single-copy loci and iii) false positive annotation of clusters that are in fact just accumulations of multi-copy loci corresponding to frequently mapped reads, but are not transcribed to piRNA precursors. RESULTS: We developed a software which detects and analyses piRNA clusters (proTRAC, probabilistic TRacking and Analysis of Clusters) based on quantifiable deviations from a hypothetical uniform distribution regarding the decisive piRNA cluster characteristics. We used piRNA sequences from human, macaque, mouse and rat to identify piRNA clusters in the respective species with proTRAC and compared the obtained results with piRNA cluster annotation from piRNABank and the results generated by different hitherto applied methods.proTRAC identified clusters not annotated at piRNABank and rejected annotated clusters based on the absence of important features like strand asymmetry. We further show, that proTRAC detects clusters that are passed over if a minimum number of single-copy piRNA loci are required and that proTRAC assigns more sequence reads per cluster since it does not preclude frequently mapped reads from the analysis. CONCLUSIONS: With proTRAC we provide a reliable tool for detection, visualization and analysis of piRNA clusters. Detected clusters are well supported by comprehensible probabilistic parameters and retain a maximum amount of information, thus overcoming the present conflict of sensitivity and specificity in piRNA cluster detection.

Sexual size dimorphism predicts rates of sequence evolution of SPerm Adhesion Molecule 1 (SPAM1, also PH-20) in monkeys, but not in hominoids (apes including humans).

Based on a dataset comprising coding DNA sequences of 23 anthropoid primates, we herein investigate if rates of sequence evolution of SPerm Adhesion Molecule1 (SPAM1, also PH-20), which participates in sperm-egg interaction, is lower in more sexually dimorphic species. For comparison, we analyze sequence evolution of apolipoproteinA-IV (APOA4) and apolipoprotein A-V (APOA5), which should evolve under less or even no sexual selection given their expression in blood, digestive tract, liver, and lungs. Regression analyses provides significant support for a negative dependence of SPAM1 derived branch-specific ratios of non-synonymous to synonymous substitution rates (dN/dS) on sexual size dimorphism (SSD) in a subsample comprising New World and Old World monkeys. We moreover observed a tendency for a positive correlation of substitution rates of SPAM1 with relative testes weight (RTW) and significantly lowered dN/dS estimates in uni-male and uni-male/multi-male breeding monkeys. Importantly, the pattern was not reproduced when analyzing partial APOA4 and APOA5 sequences. These findings illustrate that different levels of sperm competition, probably fueled by female cryptic choice, account for species-specific sequence evolution of SPAM1 in monkeys. Remarkably, present data do not support a correlation of species-specific sequence evolution of SPAM1 with sexual selection levels in hominoids (apes including humans). This can partly be ascribed to a relaxation of functional constraint of SPAM1 in some hominoid species. Additional factors confounding regression analyses specifically in hominoids might be higher levels of sperm competition than reflected by SSD and RTW in some species, a rather strong effect of female mate choice on paternity rates in others, and - in particular in humans - socio-cultural factors not measurable by SSD and RTW.

A comparative analysis to study editing of small noncoding BC200- and Alu transcripts in brain of prion-inoculated rhesus monkeys (M. Mulatta).

Small retroelements (short interspersed elements, abbreviated SINEs) are abundant in vertebrate genomes. Using RNA isolated from rhesus monkey cerebellum and buffy coat, reverse-transcription polymerase chain reaction (RT PCR) was applied to clone cDNA of BC200 and Alu RNAs. Transcripts containing Alu-SINE sequences may be subjected to extensive RNA editing by ADAR (adenosine deaminases that act on RNA) deamination. Abundance of Alu transcripts was determined with real-time RT PCR and was significantly higher than BC200 (brain cytoplasmic) in cerebellum. BC200 transcripts were absent from buffy coat cells. Availability of the rhesus genome sequence allowed the BC200 transcripts to be mapped to the specific locus on chromosome 13. Both the qualitative and quantitative characteristics of BC 200 expression argue for the BC 200 transcripts being generated by RNA polymerase III. In cerebellum, Alu transcripts often possessed base exchanges (A to G) consistent with ADAR editing and, somewhat unexpectedly, C to T exchanges consistent with APOBEC (apolipoprotein B editing complex) editing. In contrast, the BC200 transcripts, which as RNA POLIII transcripts play a role in dendritic RNA translation, appeared not to be deaminated, despite the presence of editing of Alu in the same tissue. To assess whether neuronal disease might influence editing of BC200 and Alu-SINE transcripts in cerebellum, RNA was isolated from two rhesus monkeys that were inoculated with prions from human variant Creutzfeldt-Jakob disease (vCJD). Regardless of prion-induced neurodegeneration, no BC200 RNA editing was observed, while Alu RNA continued to show both ADAR and APOBEC editing. Thus, BC200 RNAs do not appear to become accessible to editing enzymes despite infected neurons being subjected to severe stress, damage, and eventually cell death.

Elucidating geological and biological processes underlying the diversification of Sulawesi tarsiers.

Because of their exceptionally long independent evolution, a range diminution of their Eocene relatives, and a remarkable subsequent diversification in Southeast Asia, tarsiers are of particular importance to evolutionary primatologists. Little is known, however, on the processes shaping the radiation of these small enigmatic primates-especially on the Indonesian island of Sulawesi, their center of endemism. Geological reconstructions and progress in applying DNA sequence information to divergence dating now provide us with the tools and background to comprehend tarsier dispersal. Here, we describe effects of plate-tectonic movements, Pleistocene sea level changes, and hybridization on the divergence of central Sulawesi tarsiers. We analyzed 12 microsatellites, the cytochrome b gene, the hypervariable region I of the mitochondrial control region, and the sex-determining region on the Y-chromosome from 144 specimens captured along a transect crossing a species boundary and a contact zone between 2 microplates. Based on these differentially inherited genetic markers, geographic information, and recordings of vocalizations, we demonstrate that the species boundary coincides with a tectonic suture. We estimate the most recent common ancestor of the 2 taxa to have lived 1.4 Mya, we describe asymmetrical introgressive hybridization, and we give evidence of unbiased dispersal in one species and male-biased dispersal in another species. This study exemplifies that the distribution of tarsier acoustic forms on Sulawesi is consistent with the allocation of genetic variability and that plate-tectonic and glacial events have left traceable marks in the biogeography of this island's unique fauna.

Retroposon insertions provide insights into deep lagomorph evolution.

The homogenous mammalian order Lagomorpha comprises about 80 species in two families, Ochotonidae (pikas) and Leporidae (rabbits and hares). However, the phylogenetic relationships among leporids are controversial. Molecular data, particularly from mitochondrial sequences, give highly homoplasious signals. To resolve the controversy between mitochondrial and nuclear data, we analyzed genomic orthologous retroposon insertion sites, a virtually homoplasy-free marker system. From a differential screen of rabbit genomic data for intronic retroposon insertions of CSINE elements, we polymerase chain reaction-amplified and sequenced 11 retroposons in eight representative lagomorphs. We found three retroposons shared among all lagomorphs but absent in outgroups, four confirmed the monophyly of leporids, and three significantly supported Pronolagus as the sister group to all other leporids. One retroposon supported the monophyly of Lepus. The position of Pronolagus outside of the remaining leporids supports the sequence-based signals of nuclear genes and clearly refutes the misleading signals of mitochondrial genes.

Possible editing of Alu transcripts in blood cells of sporadic Creutzfeldt-Jakob disease (sCJD).

Editing of RNA molecules gained major interest when coding mRNA was analyzed. A small, noncoding, Alu DNA element transcript that may act as regulatory RNA in cells was examined in this study. Alu DNA element transcription was determined in buffy coat from healthy humans and human sporadic Creutzfeldt-Jakob disease (sCJD) cases. In addition, non-sCJD controls, mostly dementia cases and Alzheimer's disease (AD) cases, were included. The Alu cDNA sequences were aligned to genomic Alu DNA elements by database search. A comparison of best aligned Alu DNA sequences with our RNA/cDNA clones revealed editing by deamination by ADAR (adenosine deaminase acting on RNA) and APOBEC (apolipoprotein B editing complex). Nucleotide exchanges like a G instead of an A or a T instead of a C in our cDNA sequences versus genomic Alu DNA pointed to recent mutations. To confirm this, our Alu cDNA sequences were aligned not only to genomic human Alu DNA but also to the respective genomic DNA of the chimpanzee and rhesus. Enhanced ADAR correlated with A-G exchanges in dementia, AD, and sCJD was noted when compared to healthy controls as well as APOBEC-related C-T exchanges. The APOBEC-related mutations were higher in healthy controls than in cases suffering from neurodegeneration, with the exception of the dementia group with the prion protein gene (PRNP) MV genotype. Hence, this study may be considered the first real-time analysis of Alu DNA element transcripts with regard to editing of the respective Alu transcripts in human blood cells.

Pinpointing the PRDM9-PRDM7 Gene Duplication Event During Primate Divergence.

Studies on the function of PRDM9 in model systems and its evolution during vertebrate divergence shed light on the basic molecular mechanisms of hybrid sterility and its evolutionary consequences. However, information regarding PRDM9-homolog, PRDM7, whose origin is placed in the primate evolutionary tree, as well as information about the fast-evolving DNA-binding zinc finger array of strepsirrhine PRDM9 are scarce. Thus, we aimed to narrow down the date of the duplication event leading to the emergence of PRDM7 during primate evolution by comparing the phylogenetic tree reconstructions of representative primate samples of PRDM orthologs and paralogs. To confirm our PRDM7 paralogization pattern, database-deposited sequences were used to test the presence/absence patterns expected from the paralogization timing. In addition, we extended the existing phylogenetic tree of haplorrhine PRDM9 zinc fingers with their strepsirrhine counterparts. The inclusion of strepsirrhine zinc fingers completes the PRDM9 primate phylogeny. Moreover, the updated phylogeny of PRDM9 zinc fingers showed distinct clusters of strepsirrhine, tarsier, and anthropoid degenerated zinc fingers. Here, we show that PRDM7 emerged on the branch leading to the most recent common ancestor of catarrhines; therefore, its origin is more recent than previously expected. A more detailed character evolutionary study suggests that PRDM7 may have evolved differently in Cercopithecoidea as compared to Hominoidea: it lacks the first four exons in Old World monkeys orthologs and exon 10 in Papionini orthologs. Dating the origin of PRDM7 is essential for further studies investigating why Hominoidea representatives need another putative histone methyltransferase in the testis.