Mechanosensitive MiRs regulated by anabolic and catabolic loading of human cartilage.

OBJECTIVE: Elucidation of whether miRs are involved in mechanotransduction pathways by which cartilage is maintained or disturbed has a particular importance in our understanding of osteoarthritis (OA) pathophysiology. The aim was to investigate whether mechanical loading influences global miR-expression in human chondrocytes and to identify mechanosensitive miRs responding to beneficial and non-beneficial loading regimes as potential to obtain valuable diagnostic or therapeutic targets to advance OA-treatment. METHOD: Mature tissue-engineered human cartilage was subjected to two distinct loading regimes either stimulating or suppressing proteoglycan-synthesis, before global miR microarray analysis. Promising candidate miRs were selected, re-evaluated by qRT-PCR and tested for expression in human healthy vs OA cartilage samples. RESULTS: After anabolic loading, miR microarray profiling revealed minor changes in miR-expression while catabolic stimulation produced a significant regulation of 80 miRs with a clear separation of control and compressed samples by hierarchical clustering. Cross-testing of selected miRs revealed that miR-221, miR-6872-3p, miR-6723-5p were upregulated by both loading conditions while others (miR-199b-5p, miR-1229-5p, miR-1275, miR-4459, miR-6891-5p, miR-7150) responded specifically after catabolic loading. Mechanosensitivity of miR-221 correlated with pERK1/2-activation induced by both loading conditions. The miR-response to loading was transient and a constitutive deregulation of mechano-miRs in OA vs healthy articular cartilage was not observed. CONCLUSIONS: MiRs with broader vs narrower mechanosensitivity were discovered and the first group of mechanosensitive miRs characteristic for non-beneficial loading was defined that may shape the proteome differentially when cartilage tissue is disturbed. The findings prompt future investigations into miR-relevance for mechano-responsive pathways and the corresponding miR-target molecules.

Bypass in neurosurgery-indications and techniques.

Since the introduction of cerebral bypass surgery by Professor Yasargil in 1967, a plethora of literature has been published on direct cerebral revascularization. Against this background, it is remarkable that at present, only three randomized controlled trials (RCTs) exist in the field, both dealing with extracranial to intracranial bypass surgery for flow augmentation in patients at risk to suffer ischemic or hemorrhagic stroke due to cerebrovascular disease. Next to flow augmentation, the other main indication for bypass surgery is to provide flow replacement following proximal vessel sacrifice for treatment of complex aneurysms or skull base tumors. The aim of this review was to provide a comprehensive overview of the literature regarding the indications and the techniques of cerebral bypass surgery for prevention of cerebral ischemia.

Ketamine-induced prevention of SD-associated late infarct progression in experimental ischemia.

Spreading depolarizations (SDs) occur frequently in patients with malignant hemispheric stroke. In animal-based experiments, SDs have been shown to cause secondary neuronal damage and infarct expansion during the initial period of infarct progression. In contrast, the influence of SDs during the delayed period is not well characterized yet. Here, we analyzed the impact of SDs in the delayed phase after cerebral ischemia and the potential protective effect of ketamine. Focal ischemia was induced by distal occlusion of the left middle cerebral artery in C57BL6/J mice. 24 h after occlusion, SDs were measured using electrocorticography and laser-speckle imaging in three different study groups: control group without SD induction, SD induction with potassium chloride, and SD induction with potassium chloride and ketamine administration. Infarct progression was evaluated by sequential MRI scans. 24 h after occlusion, we observed spontaneous SDs with a rate of 0.33 SDs/hour which increased during potassium chloride application (3.37 SDs/hour). The analysis of the neurovascular coupling revealed prolonged hypoemic and hyperemic responses in this group. Stroke volume increased even 24 h after stroke onset in the SD-group. Ketamine treatment caused a lesser pronounced hypoemic response and prevented infarct growth in the delayed phase after experimental ischemia. Induction of SDs with potassium chloride was significantly associated with stroke progression even 24 h after stroke onset. Therefore, SD might be a significant contributor to delayed stroke progression. Ketamine might be a possible drug to prevent SD-induced delayed stroke progression.

Haploinsufficiency of protamine-1 or -2 causes infertility in mice.

Protamines are the major DNA-binding proteins in the nucleus of sperm in most vertebrates and package the DNA in a volume less than 5% of a somatic cell nucleus. Many mammals have one protamine, but a few species, including humans and mice, have two. Here we use gene targeting to determine if the second protamine provides redundancy to an essential process, or if both protamines are necessary. We disrupted the coding sequence of one allele of either Prm1 or Prm2 in embryonic stem (ES) cells derived from 129-strain mice, and injected them into blastocysts from C57BL/6-strain mice. Male chimeras produced 129-genotype sperm with disrupted Prm1 or Prm2 alleles, but failed to sire offspring carrying the 129 genome. We also found that a decrease in the amount of either protamine disrupts nuclear formation, processing of protamine-2 and normal sperm function. Our studies show that both protamines are essential and that haploinsufficiency caused by a mutation in one allele of Prm1 or Prm2 prevents genetic transmission of both mutant and wild-type alleles.

Craniectomy size and decompression of the temporal base using the altered posterior question-mark incision for decompressive hemicraniectomy.

The altered posterior question-mark incision for decompressive hemicraniectomy (DHC) was proposed to reduce the risk of intraoperative injury of the superficial temporal artery (STA) and demonstrated a reduced rate of wound-healing disorders after cranioplasty. However, decompression size during DHC is essential and it remains unclear if the new incision type allows for an equally effective decompression. Therefore, this study evaluated the efficacy of the altered posterior question-mark incision for craniectomy size and decompression of the temporal base and assessed intraoperative complications compared to a modified standard reversed question-mark incision. The authors retrospectively identified 69 patients who underwent DHC from 2019 to 2022. Decompression and preservation of the STA was assessed on postoperative CT scans and CT or MR angiography. Forty-two patients underwent DHC with the standard reversed and 27 patients with the altered posterior question-mark incision. The distance of the margin of the craniectomy to the temporal base was 6.9 mm in the modified standard reversed and 7.2 mm in the altered posterior question-mark group (p = 0.77). There was no difference between the craniectomy sizes of 158.8 mm and 158.2 mm, respectively (p = 0.45), and there was no difference in the rate of accidental opening of the mastoid air cells. In both groups, no transverse/sigmoid sinus was injured. Twenty-four out of 42 patients in the modified standard and 22/27 patients in the altered posterior question-mark group had a postoperative angiography, and the STA was preserved in all cases in both groups. Twelve (29%) and 5 (19%) patients underwent revision due to wound-healing disorders after DHC, respectively (p = 0.34). There was no difference in duration of surgery. Thus, the altered posterior question-mark incision demonstrated technically equivalent and allows for an equally effective craniectomy size and decompression of the temporal base without increasing risks of intraoperative complications. Previously described reduction in wound-healing complications and cranioplasty failures needs to be confirmed in prospective studies to demonstrate the superiority of the altered posterior question-mark incision.

Protamine-1 represents a sperm specific gene transcript: a study in Callithrix jacchus and Bos taurus.

Spermatozoa are transcriptionally inactive cells, but contain acetylated histones, normally a characteristic of transcriptionally active cells. Acetylgroups are thought to represent epigenetic marks that are transmitted to the oocyte and are involved in starting gene expression in the zygote and in regulating gene expression during early embryogenesis. We performed reverse transcription polymerase chain reaction (RT-PCR) in the common marmoset monkey (Callithrix jacchus) and in bovine spermatozoa, oocytes, zygotes, two- and four-cell embryos to evaluate the presence of specific transcripts known to play a role during fertilisation and early embryo development, namely protamine-1 (PRM1), protamine-2 (PRM2), histone H1 (H1), histone H3 (H3), histone H4 (H4), cAMP-responsive element modulator (CREM), DNA methyltransferase-1 (DNMT1), TATA box-binding protein (TBP). All transcripts tested were present in spermatozoa of the common marmoset, while bull spermatozoa lack PRM2. Marmoset oocytes exhibited transcripts for H1, H3, H4 and TBP, whereas bovine oocytes revealed H1, H3, H4, CREM, DNMT and TBP mRNAs. In zygotes, we amplified H1, H4, TBP (marmoset) and PRM1, H1, H3, H4, CREM, DNMT1 and TBP (bovine). Two-cell embryos showed PCR products for H1, H3 and TBP in the marmoset. In the bovine, all transcripts could be observed except PRM2. In four-cell embryos, PCR signals were obtained for PRM1, H1, H3, H4 and TBP in the marmoset. In the bovine, all transcripts were detected except PRM2. Our data suggest that, in both C. jacchus and Bos taurus, PRM1 transcripts are delivered by the spermatozoon to the oocyte.

Localization of protamine 1 mRNA in different stages of the cycle of the rat seminiferous epithelium.

A mouse protamine 1 cDNA probe was used to study P1 protamine gene expression during the cycle of the seminiferous epithelium in the rat. In situ hybridization experiments showed that transcription of the P1 protamine mRNA starts in the middle of step 7 of spermiogenesis during substage VIIc. The mRNA levels stay high in steps 7-14 spermatids but decrease during steps 15-16 and are virtually undetectable in steps 17-19 spermatids. Northern blot analyses of RNAs isolated from microdissected pools of seminiferous tubules show high P1 protamine mRNA concentrations during stages VIIc-XIV-III of the cycle and lower levels during stages IV-VIIb. Owing to a post-transcriptional shortening of the poly(A) tail by 130 bases, a decrease in the size of protamine 1 mRNA from approximately 580 to 450 nucleotides was observed in stages XIII-XIV suggesting an initiation of protamine 1 synthesis in step 13-14 spermatids. In stages II-VI (steps 16-18 spermatids), only the smaller size protamine 1 mRNA was detectable. The expression of protamine 1 mRNAs has been localized in the very last phase of the haploid gene activity. Although the in situ hybridization suggests a disappearance of protamine 1 mRNA after step 16 of spermiogenesis, Northern blot analysis shows that low levels of mRNA are present during the period of final condensation of the chromatin, reflecting the association of protamine with DNA.

RNA polymerase activity in bovine spermatozoa.

Washed mature spermatozoa from bulls incorporate ribonucleoside triphosphates into RNA using an endogenous template. Maximum incorporation was observed at 31 degrees C in the presence of MgCl2, all four ribonucleoside triphosphates, beta-mercaptoethanol, and glycine sodium hydroxide buffer at pH 9.0. The amount of synthesis was linearly dependent upon the concentration of spermatozoa and continued for at least 4 h. Digestion studies revealed the RNA to be present in a protected (intracellular?) location in the spermatozoa. The RNA synthesis was inhibited by ethidium bromide, rifampicin, acriflavine, actinomycin D, and caffeine, but not by alpha-amanitine or rifamycin SV. Fractionation of the spermatozoa by sonication and separation of the heads and tails by centrifugation through a discontinuous gradient revealed that more than half of the total RNA polymerase activity was associated with the tail fraction.

Haploid expression of a mouse testis alpha-tubulin gene.

A complementary DNA clone for an alpha-tubulin has been isolated from a mouse testis complementary DNA library. The untranslated 3' end of this complementary DNA is homologous to two RNA transcripts present in postmeiotic cells of the testis but absent from meiotic cells and from several tissues including brain. The temporal expression of this alpha-tubulin complementary DNA provides evidence for the haploid expression of a mammalian structural gene.

Translation of a testis-specific Cu/Zn superoxide dismutase (SOD-1) mRNA is regulated by a 65-kilodalton protein which binds to its 5' untranslated region.

Mouse testes contain two distinct superoxide dismutase (SOD-1) transcripts which differ by 114 nucleotides in their 5' untranslated regions (UTRs) (W. Gu, C. Morales, and N. B. Hecht, J. Biol. Chem. 270:236-243, 1995). The shorter SOD-1 mRNA, a somatic type SOD-I mRNA (SSOD-1), is ubiquitously expressed in all somatic tissues as well as in testes. The larger SOD-1 mRNA, a testis-specific SOD-1 mRNA (TSOD-1), derived from an alternative upstream start site, is transcribed solely in postmeiotic germ cells and is translationally regulated during spermiogenesis. Since the two mRNAs have identical nucleotides except that TSOD-1 has an additional sequence at its 5' terminus, we have proposed that the extra 5' UTR sequence may be involved in the translational control of the TSOD-1 mRNA during spermiogenesis. Here we show that, when assayed in a cell-free system, TSOD-1 is translated only slightly less efficiently than SSOD-1. RNA gel retardation and UV cross-linking assays reveal that a testicular cytoplasmic protein (Cu/Zn superoxide dismutase RNA-binding protein [SOD-RBP]) of about 65 kDa specifically binds to the extended 5' UTR of TSOD-1. After purification of SOD-RBP by RNA affinity chromatography, we demonstrate that SOD-RBP can repress the in vitro translation of TSOD-1 mRNA but not SSOD-1 mRNA or cotranslated luciferase mRNA. We conclude that SOD-RBP serves as a repressor in the translation of TSOD-1 mRNA during spermiogenesis and thereby fine-tunes the level of Cu/Zn superoxide dismutase produced in maturing germ cells.

Binding of a phosphoprotein to the 3' untranslated region of the mouse protamine 2 mRNA temporally represses its translation.

The synthesis of the protamines, the predominant nuclear proteins of mammalian spermatozoa, is regulated during germ cell development by mRNA storage for about 7 days in the cytoplasm of differentiating spermatids. Two highly conserved sequences, the Y and H elements present in the 3' untranslated regions (UTRs) of all known mammalian protamine mRNAs, form RNA-protein complexes and specifically bind a protein of 18 kDa. Here, we show that translation of fusion mRNAs was markedly repressed in reticulocyte lysates supplemented with a mouse testis extract enriched for the 18-kDa protein when the mRNAs contained the 3' UTR of mouse protamine 2 (mP2) or the Y and H elements of mP2. No significant decrease was seen when the fusion mRNAs contained the 3' UTR of human growth hormone. The 18-kDa protein is developmentally regulated in male germ cells, requires phosphorylation for RNA binding, and is found in the ribonucleoprotein particle fractions of a testicular postmitochondrial supernatant. We propose that a phosphorylated 18-kDa protein plays a primary role in repressing translation of mP2 mRNA by interaction with the highly conserved Y and H elements. At a later stage of male gamete differentiation, the 18-kDa protein no longer binds to the mRNA, likely as a result of dephosphorylation, enabling the protamine mRNA to be translated.

Mouse testes contain two size classes of actin mRNA that are differentially expressed during spermatogenesis.

Using several actin isotype-specific cDNA probes, we found actin mRNA of two size classes, 2.1 and 1.5 kilobases (kb), in extracts of polyadenylated and nonpolyadenylated RNA from sexually mature CD-1 mouse testes. Although the 2.1-kb sequence was present in both meiotic and postmeiotic testicular cell types, it decreased manyfold in late haploid cells. The 1.5-kb actin sequence was not detectable in meiotic pachytene spermatocytes (or in liver or kidney cells), but was present in round and elongating spermatids and residual bodies. To differentiate between the beta- and gamma-actin mRNAs, we isolated a cDNA, pMGA, containing the 3' untranslated region of a mouse cytoplasmic actin that has homology to the 3' untranslated region of a human gamma-actin cDNA but not to the 3' untranslated regions of human alpha-, beta-, or cardiac actins. Dot blot hybridizations with pMGA detected high levels of presumptive gamma-actin mRNA in pachytene spermatocytes and round spermatids, with lower amounts found in elongating spermatids. Hybridization with the 3' untranslated region of a rat beta-actin probe revealed that round spermatids contained higher levels of beta-actin mRNA than did pachytene spermatocytes or residual bodies. Both probes hybridized to the 2.1-kb actin mRNA but failed to hybridize to the 1.5-kb mRNA.

Identification and developmental expression of a smooth-muscle gamma-actin in postmeiotic male germ cells of mice.

Mouse testis contains two size classes of actin mRNAs of 2.1 and 1.5 kilobases (kb). The 2.1-kb actin mRNA codes for cytoplasmic beta- and gamma-actin and is found throughout spermatogenesis, while the 1.5-kb actin mRNA is first detected in postmeiotic cells. Here we identify the testicular postmeiotic actin encoded by the 1.5-kb mRNA as a smooth-muscle gamma-actin (SMGA) and present its cDNA sequence. The amino acid sequence deduced from the postmeiotic actin cDNA sequence was nearly identical to that of a chicken gizzard SMGA, with one amino acid replacement at amino acid 359, where glutamine was substituted for proline. The nucleotide sequence of the untranslated region of the SMGA differed substantially from those of other isotypes of mammalian actins. By using the 3' untranslated region of the testicular SMGA, a highly specific probe was obtained. The 1.5-kb mRNA was detected in RNA from mouse aorta, small intestine, and uterus, but not in RNA isolated from mouse brain, heart, and spleen. Testicular SMGA mRNA was first detected and increased substantially in amount during spermiogenesis in the germ cells, in contrast to the decrease of the cytoplasmic beta- and gamma-actin mRNAs towards the end of spermatogenesis. Testicular SMGA mRNA was present in the polysome fractions, indicating that it was translated. These studies demonstrate the existence of an SMGA in male haploid germ cells. The implications of the existence of an SMGA in male germ cells are discussed.

Haploid-specific transcription of protamine-myc and protamine-T-antigen fusion genes in transgenic mice.

The protamines are small, basic, arginine-rich proteins synthesized postmeiotically in the testes. Analysis of the regulation of synthesis of the protamine mRNA and protein is restricted by the difficulty in culturing and manipulating the cells in which transcription and translation occur. To avoid these problems, we have produced transgenic mice carrying fusion genes in which sequences 5' to the mouse protamine-2 gene have been linked to exons 2 and 3 of the mouse c-myc gene and, separately, to the simian virus 40 (SV40) early region. We show here that the prot.myc gene is correctly regulated; transcription is detected only in the round spermatids. In one family of transgenic mice carrying the 5' protamine-SV40 T-antigen fusion gene, SV40 early-region mRNA accumulated to the highest level in the testes but was also detected in the thymuses, brains, hearts, and preputial glands of the animals. Although we have demonstrated specific transcription of these fusion genes in the round spermatids, we were not able to detect the SV40 T-antigen protein.

DNA methylation and demethylation events during meiotic prophase in the mouse testis.

The genes encoding three different mammalian testis-specific nuclear chromatin proteins, mouse transition protein 1, mouse protamine 1, and mouse protamine 2, all of which are expressed postmeiotically, are marked by methylation early during spermatogenesis in the mouse. Analysis of DNA from the testes of prepubertal mice and isolated testicular cells revealed that transition protein 1 became progressively less methylated during spermatogenesis, while the two protamines became progressively more methylated; in contrast, the methylation of beta-actin, a gene expressed throughout spermatogenesis, did not change. These findings provide evidence that both de novo methylation and demethylation events are occurring after the completion of DNA replication, during meiotic prophase in the mouse testis.

Localization of a highly divergent mammalian testicular alpha tubulin that is not detectable in brain.

Sequence analysis of a mouse testicular alpha-tubulin partial cDNA, pRD alpha TT1, reveals an isotype that differs from both the somatic and the predominant testicular alpha tubulins at approximately 30% of the 212 amino acid residues determined. Although this mouse testicular cDNA retains the highly conserved sequence, Glu-Gly-Glu-Glu, found in the carboxyl termini of many alpha tubulins, the protein extends substantially beyond this sequence and does not terminate with a C-terminal tyrosine. Using rabbit antiserum prepared to a novel synthetic peptide predicted from this mouse testis alpha-tubulin cDNA, we have have detected by immunoblot and indirect immunofluorescence an antigenic epitope present in testicular alpha tubulin that is not detectable in brain alpha tubulins. We find that the antiserum specifically binds to the manchettes and meiotic spindles of the mouse testis but not with neural fibers or tubulin extracts of the adult mouse brain. These results demonstrate that at least one of the multiple alpha-tubulin isotypes of the mammalian testis is expressed and used in male germ cells but not in the brain.

Mouse protamine 2 is synthesized as a precursor whereas mouse protamine 1 is not.

The nuclei of mouse spermatozoa contain two protamine variants, mouse protamine 1 (mP1) and mouse protamine 2 (mP2). The amino acid sequence predicted from mP1 cDNAs demonstrates that mP1 is a 50-amino-acid protein with strong homology to other mammalian P1 protamines. Nucleotide sequence analysis of independently isolated, overlapping cDNA clones indicated that mP2 is initially synthesized as a precursor protein which is subsequently processed into the spermatozoan form of mP2. The existence of the mP2 precursor was confirmed by amino acid composition and sequence analysis of the largest of a set of four basic proteins isolated from late-step spermatids whose synthesis is coincident with that of mP1. The sequence of the first 10 amino acids of this protein, mP2 precursor 1, exactly matches that predicted from the nucleotide sequence of cDNA and genomic mP2 clones. The amino acid composition of isolated mP2 precursor 1 very closely matches that predicted from the mP2 cDNA nucleotide sequence. Sequence analysis of the amino terminus of isolated mature mP2 identified the final processing point within the mP2 precursor. These studies demonstrated that mP2 is synthesized as a precursor containing 106 amino acids which is processed into the mature, 63-amino-acid form found in spermatozoa.

An SNP in protamine 1: a possible genetic cause of male infertility?

Gene targeting of the sperm nuclear proteins, the protamines, in mice leads to haploinsufficiency, abnormal chromatin compaction, sperm DNA damage, and male infertility. In order to investigate whether changes in amount or structure of the protamines could be a cause of human infertility, we sequenced the protamine genes of infertile men whose sperm appeared phenotypically similar to those of protamine deficient mice. We identified a heterozygous single nucleotide polymorphism (SNP) in the protamine (PRM1) gene in three infertile men (10% of the total infertile men analysed). This SNP disrupts one of the highly conserved arginine clusters needed for normal DNA binding. To rapidly screen for this SNP in infertile patients, we developed a simple PCR restriction fragment length polymorphism assay. This is the first report of a SNP in the PRM1 gene that appears associated with human male infertility.

Altering the GTP binding site of the DNA/RNA-binding protein, Translin/TB-RBP, decreases RNA binding and may create a dominant negative phenotype.

The DNA/RNA-binding protein, Translin/Testis Brain RNA-binding protein (Translin/TB-RBP), contains a putative GTP binding site in its C-terminus which is highly conserved. To determine if guanine nucleotide binding to this site functionally alters nucleic acid binding, electrophoretic mobility shift assays were performed with RNA and DNA binding probes. GTP, but not GDP, reduces RNA binding by approximately 50% and the poorly hydrolyzed GTP analog, GTPgammaS, reduces binding by >90% in gel shift and immunoprecipitation assays. No similar reduction of DNA binding is seen. When the putative GTP binding site of TB-RBP, amino acid sequence VTAGD, is altered to VTNSD by site directed mutagenesis, GTP will no longer bind to TB-RBP(GTP) and TB-RBP(GTP) no longer binds to RNA, although DNA binding is not affected. Yeast two-hybrid assays reveal that like wild-type TB-RBP, TB-RBP(GTP) will interact with itself, with wild-type TB-RBP and with Translin associated factor X (Trax). Transfection of TB-RBP(GTP) into NIH 3T3 cells leads to a marked increase in cell death suggesting a dominant negative function for TB-RBP(GTP) in cells. These data suggest TB-RBP is an RNA-binding protein whose activity is allosterically controlled by nucleotide binding.

The relationship between two murine DNA-dependent DNA polymerases from the cytosol and the low molecular weight DNA polymerase.

After aqueous subcellular fractionation and partial purification by phosphocellulose chromatography, murine cells are found to contain a low molecular weight DNA-dependent DNA polymerase (beta) in the nuclear fraction and two distinguishable DNA-dependent DNA polymerases (C-I and C-II) in the cytosol. Both C-I and C-II are found in testis, liver, and regenerating liver; the amount of C-I being several fold increased in the regenerating liver and in immature testis. C-I and C-II are distinguishable by the criteria of salt sensitivity, inhibition by single-stranded DNA, elution from phosphocellulose, inhibition by 0.3 mM N-ethylmaleimide, template preference, and sedimentation coefficient. C-II is dissociated by 0.25 M KC1 to an active form of DNA polymerase of sedimentation coefficient 3.5 S while C-I is not dissociated, maintaining its sedimentation coefficient of 7.2 S. Many similar chemical and physical properties of C-II and the low molecular weight nuclear DNA polymerase (beta) suggest that C-II may represent an aggregate state of beta monomers, The size, reaction properties and the increase in enzyme activity under conditions of rapid cellular proliferation suggest C-I is analogous to the alpha DNA polymerase.