RESUMO
The structural maintenance of chromosome (SMC) complexes-cohesin and condensins-are crucial for chromosome separation and compaction during cell division. During the interphase, mammalian cohesins additionally fold the genome into loops and domains. Here we show that, in Caenorhabditis elegans, a species with holocentric chromosomes, condensin I is the primary, long-range loop extruder. The loss of condensin I and its X-specific variant, condensin IDC, leads to genome-wide decompaction, chromosome mixing and disappearance of X-specific topologically associating domains, while reinforcing fine-scale epigenomic compartments. In addition, condensin I/IDC inactivation led to the upregulation of X-linked genes and unveiled nuclear bodies grouping together binding sites for the X-targeting loading complex of condensin IDC. C. elegans condensin I/IDC thus uniquely organizes holocentric interphase chromosomes, akin to cohesin in mammals, as well as regulates X-chromosome gene expression.
Assuntos
Adenosina Trifosfatases , Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Proteínas de Ligação a DNA , Complexos Multiproteicos , Cromossomo X , Animais , Caenorhabditis elegans/genética , Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Cromossomo X/genética , Proteínas Cromossômicas não Histona/metabolismo , Proteínas Cromossômicas não Histona/genética , Coesinas , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/genética , Interfase/genética , Genoma Helmíntico , Genes Ligados ao Cromossomo X , Cromossomos/genéticaRESUMO
Nucleic acid aptamers have been used in the past for the development of diagnostic methods against a number of targets such as bacteria, pesticides, cancer cells etc. In the present study, six rounds of Cell-SELEX were performed on a ssDNA aptamer library against X-enriched sperm cells from Sahiwal breed cattle. Sequencing was used to examine the aptamer sequences that shown affinity for sperm carrying the X chromosome in order to find any possible X-sperm-specific sequences. Out of 35 identified sequences, 14 were selected based on bioinformatics analysis like G-Score and Mfold structures. Further validation of their specificity was done via fluorescence microscopy. The interaction of biotinylated-aptamer with sperm was also determined by visualizing the binding of streptavidin coated magnetic beads on the head region of the sperm under bright field microscopy. Finally, a real-time experiment was designed for the validation of X-sperm enrichment by synthesized aptamer sequences. Among the studied sequences, aptamer 29a exhibited a higher affinity for X sperm compared to Y sperm in a mixed population of sperm cells. By using aptamer sequence 29a, we obtained an enrichment of 70% for X chromosome bearing sperm cells.
Assuntos
Aptâmeros de Nucleotídeos , Técnica de Seleção de Aptâmeros , Espermatozoides , Cromossomo X , Masculino , Animais , Aptâmeros de Nucleotídeos/química , Aptâmeros de Nucleotídeos/genética , Espermatozoides/química , Bovinos , Cromossomo X/genética , Técnica de Seleção de Aptâmeros/métodosRESUMO
Condensins are evolutionarily conserved molecular motors that translocate along DNA and form loops. To address how DNA topology affects condensin translocation, we applied auxin-inducible degradation of topoisomerases I and II and analyzed the binding and function of an interphase condensin that mediates X chromosome dosage compensation in C. elegans. TOP-2 depletion reduced long-range spreading of condensin-DC (dosage compensation) from its recruitment sites and shortened 3D DNA contacts measured by Hi-C. TOP-1 depletion did not affect long-range spreading but resulted in condensin-DC accumulation within expressed gene bodies. Both TOP-1 and TOP-2 depletion resulted in X chromosome derepression, indicating that condensin-DC translocation at both scales is required for its function. Together, the distinct effects of TOP-1 and TOP-2 suggest two distinct modes of condensin-DC association with chromatin: long-range DNA loop extrusion that requires decatenation/unknotting of DNA and short-range translocation across genes that requires resolution of transcription-induced supercoiling.
Assuntos
Adenosina Trifosfatases , Caenorhabditis elegans , Animais , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Adenosina Trifosfatases/metabolismo , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Cromossomo X/genética , Cromossomo X/metabolismo , Cromossomos/metabolismoRESUMO
Dosage balance between sex chromosomes and autosomes can be achieved through diverse mechanisms across vertebrates and invertebrates. A new study discovers a key player that contributes to X chromosome upregulation (XCU) during early mouse development and associates the dysregulation of XCU with human bile duct cancer pathogenesis.
Assuntos
Mecanismo Genético de Compensação de Dose , Cromossomo X , Animais , Humanos , Camundongos , Regulação para Cima , Cromossomo X/genética , Cromossomos Sexuais , Invertebrados/genéticaRESUMO
Females have two X chromosomes and males have only one in most mammals. X chromosome inactivation (XCI) occurs in females to equalize X-dosage between sexes. Besides, mammals also balance the dosage between X chromosomes and autosomes via X chromosome upregulation (XCU) to fine-tune X-linked expression and thus maintain genomic homeostasis. Despite some studies highlighting the importance of XCU in somatic cells, little is known about how XCU is achieved and its developmental role during early embryogenesis. Herein, using mouse preimplantation embryos as the model, we reported that XCU initially occurs upon major zygotic genome activation and co-regulates X-linked expression in cooperation with imprinted XCI during preimplantation development. An in-depth analysis further indicated, unexpectedly, only a small proportion of, but not X chromosome-wide, X-linked genes contribute greatly to XCU. Furthermore, we identified that bromodomain containing 4 (BRD4) plays a key role in the transcription activation of XCU during preimplantation development. BRD4 deficiency or inhibition caused an impaired XCU, thus leading to reduced developmental potential and mitochondrial dysfunctions of blastocysts. Our finding was also supported by the tight association of BRD4 dysregulation and XCU disruption in the pathology of cholangiocarcinoma. Thus, our results not only advanced the current knowledge of X-dosage compensation and provided a mechanism for understanding XCU initiation but also presented an important clue for understanding the developmental and pathological role of XCU.
Assuntos
Desenvolvimento Embrionário , Genes Ligados ao Cromossomo X , Proteínas Nucleares , Fatores de Transcrição , Animais , Feminino , Masculino , Camundongos , Proteínas Nucleares/genética , Fatores de Transcrição/genética , Ativação Transcricional , Regulação para Cima , Cromossomo X/genética , Embrião de MamíferosRESUMO
Cancer-related genes are under intense evolutionary pressure. In this study, we conjecture that X-linked tumor suppressor genes (TSG) are not protected by the Knudson's two-hit mechanism and are therefore subject to negative selection. Accordingly, nearly all mammalian species exhibited lower TSG-to-noncancer gene ratios on their X chromosomes compared with nonmammalian species. Synteny analysis revealed that mammalian X-linked TSGs were depleted shortly after the emergence of the XY sex-determination system. A phylogeny-based model unveiled a higher X chromosome-to-autosome relocation flux for human TSGs. This was verified in other mammals by assessing the concordance/discordance of chromosomal locations of mammalian TSGs and their orthologs in Xenopus tropicalis. In humans, X-linked TSGs are younger or larger in size. Consistently, pan-cancer analysis revealed more frequent nonsynonymous somatic mutations of X-linked TSGs. These findings suggest that relocation of TSGs out of the X chromosome could confer a survival advantage by facilitating evasion of single-hit inactivation. SIGNIFICANCE: This work unveils extensive trafficking of TSGs from the X chromosome to autosomes during evolution, thus identifying X-linked TSGs as a genetic Achilles' heel in tumor suppression.
Assuntos
Evolução Molecular , Genes Supressores de Tumor , Neoplasias , Cromossomo X , Animais , Humanos , Mamíferos/genética , Neoplasias/genética , Oncogenes , Sintenia , Cromossomo X/genética , XenopusRESUMO
Abnormalities in chromosome number have the potential to disrupt the balance of gene expression and thereby decrease organismal fitness and viability. Such abnormalities occur in most solid tumors and also cause severe developmental defects and spontaneous abortions. In contrast to the imbalances in chromosome dose that cause pathologies, the difference in X-chromosome dose used to determine sexual fate across diverse species is well tolerated. Dosage compensation mechanisms have evolved in such species to balance X-chromosome gene expression between the sexes, allowing them to tolerate the difference in X-chromosome dose. This review analyzes the chromosome counting mechanism that tallies X-chromosome number to determine sex (XO male and XX hermaphrodite) in the nematode Caenorhabditis elegans and the associated dosage compensation mechanism that balances X-chromosome gene expression between the sexes. Dissecting the molecular mechanisms underlying X-chromosome counting has revealed how small quantitative differences in intracellular signals can be translated into dramatically different fates. Dissecting the process of X-chromosome dosage compensation has revealed the interplay between chromatin modification and chromosome structure in regulating gene expression over vast chromosomal territories.
Assuntos
Proteínas de Caenorhabditis elegans , Mecanismo Genético de Compensação de Dose , Animais , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Transtornos do Desenvolvimento Sexual , Feminino , Genes Ligados ao Cromossomo X , Masculino , Cromossomo X/genética , Cromossomo X/metabolismoRESUMO
Posttranslational histone modifications are critical for the regulation of genome function. The levels of histone modifications oscillate during the cell cycle. Most modifications are diluted after DNA replication and then their levels are restored during the rest of the cell cycle with different kinetics depending on the modification. Some modifications, like histone H4 Lys20 monomethylation (H4K20me1), exhibit cell cycle-dependent dynamic changes. To track histone modifications in living cells, we have developed genetically encoded probes termed modification specific intracellular antibodies, or "mintbodies." As mintbodies shuttle between the cytoplasm and nucleus by diffusion, their nuclear concentration depends on the target modification level. By measuring the nuclear to cytoplasmic intensity ratio of H4K20me1-specific mintbody, we have monitored the increase of H4K20me1 in the G2 phase. Here we describe how the mintbody-based methods can be applied to track a specific chromosome, such as the inactive X chromosome (Xi), on which genes are repressed through histone H3 Lys27 trimethylation (H3K27me3). When H3K27me3-specific mintbodies are expressed in cells that harbor Xi, the mintbodies are concentrated on Xi and the dynamic behavior of Xi can be tracked using a confocal microscope. After acquiring 3D time-lapse images, an image analysis allows measuring the volume, shape and H3K27me3 level of Xi during the cell cycle.
Assuntos
Corantes Fluorescentes/química , Histonas/metabolismo , Inativação do Cromossomo X , Cromossomo X/genética , Animais , Ciclo Celular , Linhagem Celular Tumoral , Células HeLa , Código das Histonas , Histonas/química , Humanos , Metilação , Camundongos , Microscopia Confocal , Imagem com Lapso de Tempo , Cromossomo X/químicaRESUMO
During X chromosome inactivation (XCI), the inactive X chromosome (Xi) is recruited to the nuclear lamina at the nuclear periphery. Beside X chromosome reactivation resulting in a highly penetrant aging-like hematopoietic malignancy, little is known about XCI in aged hematopoietic stem cells (HSCs). Here, we demonstrate that LaminA/C defines a distinct repressive nuclear compartment for XCI in young HSCs, and its reduction in aged HSCs correlates with an impairment in the overall control of XCI. Integrated omics analyses reveal higher variation in gene expression, global hypomethylation, and significantly increased chromatin accessibility on the X chromosome (Chr X) in aged HSCs. In summary, our data support the role of LaminA/C in the establishment of a special repressive compartment for XCI in HSCs, which is impaired upon aging.
Assuntos
Senescência Celular/genética , Células-Tronco Hematopoéticas/metabolismo , Inativação do Cromossomo X/genética , Animais , Cromatina/metabolismo , Sequenciamento de Cromatina por Imunoprecipitação , Humanos , Lamina Tipo A/metabolismo , Camundongos Endogâmicos C57BL , Transposases/metabolismo , Cromossomo X/genéticaRESUMO
Sex determination in mammals is usually provided by a pair of chromosomes, XX in females and XY in males. Mole voles of the genus Ellobius are exceptions to this rule. In Ellobius tancrei, both males and females have a pair of XX chromosomes that are indistinguishable from each other in somatic cells. Nevertheless, several studies on Ellobius have reported that the two X chromosomes may have a differential organization and behavior during male meiosis. It has not yet been demonstrated if these differences also appear in female meiosis. To test this hypothesis, we have performed a comparative study of chromosome synapsis, recombination, and histone modifications during male and female meiosis in E. tancrei. We observed that synapsis between the two X chromosomes is limited to the short distal (telomeric) regions of the chromosomes in males, leaving the central region completely unsynapsed. This uneven behavior of sex chromosomes during male meiosis is accompanied by structural modifications of one of the X chromosomes, whose axial element tends to appear fragmented, accumulates the heterochromatin mark H3K9me3, and is associated with a specific nuclear body that accumulates epigenetic marks and proteins such as SUMO-1 and centromeric proteins but excludes others such as H3K4me, ubiH2A, and γH2AX. Unexpectedly, sex chromosome synapsis is delayed in female meiosis, leaving the central region unsynapsed during early pachytene. This region accumulates γH2AX up to the stage in which synapsis is completed. However, there are no structural or epigenetic differences similar to those found in males in either of the two X chromosomes. Finally, we observed that recombination in the sex chromosomes is restricted in both sexes. In males, crossover-associated MLH1 foci are located exclusively in the distal regions, indicating incipient differentiation of one of the sex chromosomes into a neo-Y. Notably, in female meiosis, the central region of the X chromosome is also devoid of MLH1 foci, revealing a lack of recombination, possibly due to insufficient homology. Overall, these results reveal new clues about the origin and evolution of sex chromosomes.
Assuntos
Arvicolinae , Caracteres Sexuais , Animais , Arvicolinae/genética , Feminino , Masculino , Meiose , Cromossomos Sexuais/genética , Cromossomo X/genética , Cromossomo Y/genéticaRESUMO
BACKGROUND: Stroke is a sexually dimorphic disease. Previous studies have found that young females are protected against ischemia compared to males, partially due to the protective effect of ovarian hormones, particularly estrogen (E2). However, there are also genetic and epigenetic effects of X chromosome dosage that contribute to stroke sensitivity and neuroinflammation after injury, especially in the aged. Genes that escape from X chromosome inactivation (XCI) contribute to sex-specific phenotypes in many disorders. Kdm5c and kdm6a are X escapee genes that demethylate H3K4me3 and H3K27me3, respectively. We hypothesized that the two demethylases play critical roles in mediating the stroke sensitivity. METHODS: To identify the X escapee genes involved in stroke, we performed RNA-seq in flow-sorted microglia from aged male and female wild type (WT) mice subjected to middle cerebral artery occlusion (MCAO). The expression of these genes (kdm5c/kdm6a) were confirmed in four core genotypes (FCG) mice and in post-mortem human stroke brains by immunohistochemistry (IHC), Western blot, and RT-PCR. Chromatin immunoprecipitation (ChIP) assays were conducted to detect DNA levels of inflammatory interferon regulatory factor (IRF) 4/5 precipitated by histone H3K4 and H3K27 antibodies. Manipulation of kdm5c/kdm6a expression with siRNA or lentivirus was performed in microglial culture, to determine downstream pathways and examine the regulatory roles in inflammatory cytokine production. RESULTS: Kdm5c and kdm6a mRNA levels were significantly higher in aged WT female vs. male microglia, and the sex difference also existed in ischemic brains from FCG mice and human stroke patients. The ChIP assay showed the IRF 4/5 had higher binding levels to demethylated H3K4 or H3K27, respectively, in female vs. male ischemic microglia. Knockdown or over expression of kdm5c/kdm6a with siRNA or lentivirus altered the methylation of H3K4 or H3K27 at the IRF4/5 genes, which in turn, impacted the production of inflammatory cytokines. CONCLUSIONS: The KDM-Histone-IRF pathways are suggested to mediate sex differences in cerebral ischemia. Epigenetic modification of stroke-related genes constitutes an important mechanism underlying the ischemic sexual dimorphism.
Assuntos
Epigênese Genética/genética , Inflamação/genética , AVC Isquêmico/genética , Caracteres Sexuais , Cromossomo X/genética , Idoso , Idoso de 80 Anos ou mais , Animais , Imunoprecipitação da Cromatina , Citocinas/biossíntese , Feminino , Genótipo , Histona Desmetilases/genética , Humanos , Masculino , Camundongos , Pessoa de Meia-Idade , RNA Interferente Pequeno/genética , Transdução de Sinais/genéticaRESUMO
The current COVID-19 pandemic is caused by infections with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A sex-bias has been observed, with increased susceptibility and mortality in male compared to female patients. The gene for the SARS-CoV-2 receptor ACE2 is located on the X chromosome. We previously generated TP53 mutant pigs that exhibit a sex-specific patho-phenotype due to altered regulation of numerous X chromosome genes. In this study, we explored the effect of p53 deficiency on ACE2 expression in pigs. First, we identified the p53 binding site in the ACE2 promoter and could show its regulatory effect on ACE2 expression by luciferase assay in porcine primary kidney fibroblast cells. Later, quantitative PCR and western blot showed tissue- and gender-specific expression changes of ACE2 and its truncated isoform in p53-deficient pigs. We believe these findings will broaden the knowledge on ACE2 regulation and COVID-19 susceptibility.
Assuntos
Enzima de Conversão de Angiotensina 2/metabolismo , Regulação da Expressão Gênica , Especificidade de Órgãos , Caracteres Sexuais , Sus scrofa/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Enzima de Conversão de Angiotensina 2/química , Enzima de Conversão de Angiotensina 2/genética , Animais , Sequência de Bases , Sítios de Ligação , COVID-19/metabolismo , COVID-19/virologia , Modelos Animais de Doenças , Feminino , Fibroblastos , Deleção de Genes , Masculino , Regiões Promotoras Genéticas/genética , Proteína Supressora de Tumor p53/deficiência , Proteína Supressora de Tumor p53/genética , Cromossomo X/genéticaRESUMO
Owing to bursts in the expression of thousands of germline-specific genes, the testis has the most diverse and complex transcriptome of all organs. By analyzing the male germline of mice, we demonstrate that the genome-wide reorganization of super-enhancers (SEs) drives bursts in germline gene expression after the mitosis-to-meiosis transition. SE reorganization is regulated by two molecular events: the establishment of meiosis-specific SEs via A-MYB (MYBL1), a key transcription factor for germline genes, and the resolution of SEs in mitotically proliferating cells via SCML2, a germline-specific Polycomb protein required for spermatogenesis-specific gene expression. Before entry into meiosis, meiotic SEs are preprogrammed in mitotic spermatogonia to ensure the unidirectional differentiation of spermatogenesis. We identify key regulatory factors for both mitotic and meiotic enhancers, revealing a molecular logic for the concurrent activation of mitotic enhancers and suppression of meiotic enhancers in the somatic and/or mitotic proliferation phases.
Assuntos
Elementos Facilitadores Genéticos , Meiose/genética , Mitose/genética , Proteínas do Grupo Polycomb/genética , Proteínas Proto-Oncogênicas c-myb/genética , Espermatogênese/genética , Transativadores/genética , Animais , Diferenciação Celular , Regulação da Expressão Gênica , Masculino , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mutação , Proteínas do Grupo Polycomb/metabolismo , Proteínas Proto-Oncogênicas c-myb/metabolismo , Espermatogônias/citologia , Espermatogônias/fisiologia , Transativadores/metabolismo , Cromossomo X/genéticaRESUMO
Human sperm protein associated with the nucleus on the X chromosome (SPANX) genes encode a protein family (SPANX-A, -B, -C and -D), whose expression is limited to the testis and spermatozoa in normal tissues and to a wide variety of tumour cells. Present only in hominids, SPANX-A/D is exclusively expressed in post-meiotic spermatids and mature spermatozoa. However, the biological role of the protein family in human spermatozoa is largely unknown. Combining proteomics and molecular approaches, the present work describes the presence of all isoforms of SPANX-A/D in human spermatozoa and novel phosphorylation sites of this protein family. In addition, we identify 307 potential SPANX-A/D interactors related to nuclear envelop, chromatin organisation, metabolism and cilia movement. Specifically, SPANX-A/D interacts with fumarate hydratase and colocalises with both fumarate hydratase and Tektin 1 proteins, involved in meeting energy demands for sperm motility, and with nuclear pore complex nucleoporins. We provide insights into the molecular features of sperm physiology describing for the first time a multifunctional role of SPANX-A/D protein family in nuclear envelope, sperm movement and metabolism, considered key functions for human spermatozoa. SPANX-A/D family members, therefore, might be promising targets for sperm fertility management.
Assuntos
Proteínas Nucleares/metabolismo , Motilidade dos Espermatozoides/fisiologia , Espermatozoides/metabolismo , Sequência de Aminoácidos , Animais , Linhagem Celular , Linhagem Celular Tumoral , Núcleo Celular/genética , Núcleo Celular/metabolismo , Cromatina/genética , Células HEK293 , Células HeLa , Hominidae/metabolismo , Humanos , Masculino , Membrana Nuclear/metabolismo , Fosforilação/genética , Isoformas de Proteínas/metabolismo , Proteômica/métodos , Homologia de Sequência de Aminoácidos , Espermátides/metabolismo , Testículo/metabolismo , Fatores de Transcrição/metabolismo , Cromossomo X/genéticaRESUMO
Long thought to be dispensable after establishing X chromosome inactivation (XCI), Xist RNA is now known to also maintain the inactive X (Xi). To what extent somatic X reactivation causes physiological abnormalities is an active area of inquiry. Here, we use multiple mouse models to investigate in vivo consequences. First, when Xist is deleted systemically in post-XCI embryonic cells using the Meox2-Cre driver, female pups exhibit no morbidity or mortality despite partial X reactivation. Second, when Xist is conditionally deleted in epithelial cells using Keratin14-Cre or in B cells using CD19-Cre, female mice have a normal life span without obvious illness. Third, when Xist is deleted in gut using Villin-Cre, female mice remain healthy despite significant X-autosome dosage imbalance. Finally, when the gut is acutely stressed by azoxymethane/dextran sulfate (AOM/DSS) exposure, both Xist-deleted and wild-type mice develop gastrointestinal tumors. Intriguingly, however, under prolonged stress, mutant mice develop larger tumors and have a higher tumor burden. The effect is female specific. Altogether, these observations reveal a surprising systemic tolerance to Xist loss but importantly reveal that Xist and XCI are protective to females during chronic stress.
Assuntos
Neoplasias Gastrointestinais/fisiopatologia , Doenças Genéticas Ligadas ao Cromossomo X/genética , Doenças Genéticas Ligadas ao Cromossomo X/microbiologia , RNA Longo não Codificante/genética , Cromossomo X/genética , Animais , Feminino , Neoplasias Gastrointestinais/etiologia , Neoplasias Gastrointestinais/genética , Neoplasias Gastrointestinais/metabolismo , Trato Gastrointestinal/metabolismo , Doenças Genéticas Ligadas ao Cromossomo X/complicações , Doenças Genéticas Ligadas ao Cromossomo X/metabolismo , Humanos , Masculino , Camundongos , RNA Longo não Codificante/metabolismo , Estresse Fisiológico , Carga Tumoral , Inativação do Cromossomo XRESUMO
A GWAS was performed for inborn X-linked facial dysmorphia with severe growth retardation in Labrador Retrievers. This lethal condition was mapped on the X chromosome at 17-21 Mb and supported by eight SNPs in complete LD. Dams of affected male puppies were heterozygous for the significantly associated SNPs and male affected puppies carried the associated alleles hemizygously. In the near vicinity to the associated region, RPS6KA3 was identified as a candidate gene causing facial dysmorphia in humans and mice known as Coffin-Lowry syndrome. Haplotype analysis showed significant association with the phenotypes of all 18 animals under study. This haplotype was validated through normal male progeny from a dam with the not-associated haplotype on both X chromosomes but male affected full-sibs with the associated haplotype.
Assuntos
Craniossinostoses/veterinária , Doenças do Cão/genética , Cães/genética , Genes Letais , Proteínas Quinases S6 Ribossômicas 90-kDa/genética , Animais , Craniossinostoses/genética , Feminino , Estudos de Associação Genética/veterinária , Haplótipos , Masculino , Linhagem , Fenótipo , Polimorfismo de Nucleotídeo Único , Cromossomo X/genéticaRESUMO
Justificación:Las repeticiones cortas en tándem (STRs) están distribuidos por toda la extensión del genoma humano, los ubicados en los cromosomas autosómicos y en el cromosoma Y han sido ampliamente utilizados en los laboratorios de genética forense debido a las características y patrones hereditarios que estos poseen. ObjetivoA fin de caracterizar y determinar parámetros de interés forense en secuencias de tipo STR del cromosoma X (DXS8378, DXS9902, DXS7132, DXS9898, DXS6809, DXS6789, DXS7133, GATA172D05, GATA31E08 y DXS7423) en la población del Estado Zulia.Metodología:Se eligieron 108 individuos (130 cromosomas X),cuyos ADN se amplificaron mediante la reacción en cadena de la polimerasa, los fragmentos se separaron por electroforesis capilar y los alelos reportadoscon respecto a la escalera alélica. Resultados: El contenido de información polimórfica demostró ser mayor de 0,5 en todos los microsatélites y el poder de discriminación acumulado fue de 0,99999997 en mujeres y 0,99999816 en hombres.Conclusiones:Los datos demuestran que los microsatélites del cromosoma X analizados son lo suficientemente informativos como para ser utilizados en casos de vínculos biológicos complejos y la identificación humana...(AU)
Assuntos
Humanos , Cromossomo X/genética , Repetições de Microssatélites , Genética Forense/métodos , Medicina Legal/métodosRESUMO
Mechanisms establishing higher-order chromosome structures and their roles in gene regulation are elusive. We analyzed chromosome architecture during nematode X chromosome dosage compensation, which represses transcription via a dosage-compensation condensin complex (DCC) that binds hermaphrodite Xs and establishes megabase-sized topologically associating domains (TADs). We show that DCC binding at high-occupancy sites (rex sites) defines eight TAD boundaries. Single rex deletions disrupted boundaries, and single insertions created new boundaries, demonstrating that a rex site is necessary and sufficient to define DCC-dependent boundary locations. Deleting eight rex sites (8rexΔ) recapitulated TAD structure of DCC mutants, permitting analysis when chromosome-wide domain architecture was disrupted but most DCC binding remained. 8rexΔ animals exhibited no changes in X expression and lacked dosage-compensation mutant phenotypes. Hence, TAD boundaries are neither the cause nor the consequence of DCC-mediated gene repression. Abrogating TAD structure did, however, reduce thermotolerance, accelerate aging, and shorten lifespan, implicating chromosome architecture in stress responses and aging.
Assuntos
Mecanismo Genético de Compensação de Dose/genética , Regulação da Expressão Gênica/genética , Longevidade/fisiologia , Cromossomo X/genética , Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Animais , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismoRESUMO
The synaptonemal complex (SC) is a proteinaceous scaffold required for synapsis and recombination between homologous chromosomes during meiosis. Although the SC has been linked to differences in genome-wide crossover rates, the genetic basis of standing variation in SC structure remains unknown. To investigate the possibility that recombination evolves through changes to the SC, we characterized the genetic architecture of SC divergence on two evolutionary timescales. Applying a novel digital image analysis technique to spermatocyte spreads, we measured total SC length in 9,532 spermatocytes from recombinant offspring of wild-derived mouse strains with differences in this fundamental meiotic trait. Using this large dataset, we identified the first known genomic regions involved in the evolution of SC length. Distinct loci affect total SC length divergence between and within subspecies, with the X chromosome contributing to both. Joint genetic analysis of MLH1 foci-immunofluorescent markers of crossovers-from the same spermatocytes revealed that two of the identified loci also confer differences in the genome-wide recombination rate. Causal mediation analysis suggested that one pleiotropic locus acts early in meiosis to designate crossovers prior to SC assembly, whereas a second locus primarily shapes crossover number through its effect on SC length. One genomic interval shapes the relationship between SC length and recombination rate, likely modulating the strength of crossover interference. Our findings pinpoint SC formation as a key step in the evolution of recombination and demonstrate the power of genetic mapping on standing variation in the context of the recombination pathway.
Assuntos
Troca Genética , Variação Genética , Proteína 1 Homóloga a MutL/genética , Complexo Sinaptonêmico/genética , Cromossomo X/genética , Animais , Mapeamento Cromossômico/métodos , Evolução Molecular , Loci Gênicos , Ensaios de Triagem em Larga Escala/métodos , Processamento de Imagem Assistida por Computador , Masculino , Camundongos , Microscopia de Fluorescência , Proteína 1 Homóloga a MutL/metabolismo , Espermatócitos/metabolismo , Complexo Sinaptonêmico/metabolismo , Cromossomo X/metabolismoRESUMO
Implantation of the blastocyst into the uterus is the gateway for further embryonic development in mammals. Programming of blastocyst to an implantation-competent state known as blastocyst activation is the determining factor for implantation into the receptive uterus. However, it remains largely unclear how the blastocyst is globally programmed for implantation. Employing a delayed implantation mouse model, we show here that the blastocyst undergoes extensive programming essential for implantation. By analyzing the transcriptional profile of blastocysts with different implantation competency, we reveal the dynamic change in the biosynthesis, metabolism, and proliferation during blastocyst reactivation from diapause. We also demonstrate that reactivation of the X chromosome, one of the most important events during periimplantation of female embryonic development, is not completed even in blastocysts under conditions of dormancy, despite long term suspension in the uterus. Moreover, the mural trophectoderm (TE), but not the polar TE, differentiates to be more invasive through the weakened cell-cell tight junctions and extracellular matrices (ECMs). By analyzing the differentially expressed profile of secretory proteins, we further demonstrate that the blastocyst functions as a proinflammatory body to secrete proinflammatory signals, such as TNFα and S100A9, thereby triggering embryo-uterine attachment reaction during implantation. Collectively, our data systematically and comprehensively disclose the programming of blastocyst reactivation from diapause for implantation and uncover previously undefined roles of blastocyst during implantation.