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Search Results: 1 - 10 of 12066 matches for " germline x-chromosome inactivation "
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Demasculinization of the Anopheles gambiae X chromosome
Kalle Magnusson, Gareth J Lycett, Antonio M Mendes, Amy Lynd, Philippos-Aris Papathanos, Andrea Crisanti, Nikolai Windbichler
BMC Evolutionary Biology , 2012, DOI: 10.1186/1471-2148-12-69
Abstract: We performed a meta-analysis of sex-biased gene expression in Anopheles gambiae which provides evidence for a general underrepresentation of male-biased genes on the X-chromosome that increased in significance with the observed degree of sex-bias. A phylogenomic comparison between Drosophila melanogaster, Aedes aegypti and Culex quinquefasciatus also indicates that the Anopheles X chromosome strongly disfavours the evolutionary conservation of male-biased expression and that novel male-biased genes are more likely to arise on autosomes. Finally, we demonstrate experimentally that transgenes situated on the Anopheles gambiae X chromosome are transcriptionally silenced in the male germline.The data presented here support the hypothesis that the observed demasculinization of the Anopheles X chromosome is driven by X-chromosome inactivation in the male germline and by sexual antagonism. The demasculinization appears to be the consequence of a loss of male-biased expression, rather than a failure in the establishment or the extinction of male-biased genes.
Prognostic value of X-chromosome inactivation in symptomatic female carriers of dystrophinopathy
Juan-Mateu Jonàs,Rodríguez Maria,Nascimento Andrés,Jiménez-Mallebrera Cecilia
Orphanet Journal of Rare Diseases , 2012, DOI: 10.1186/1750-1172-7-82
Abstract: Background Between 8% and 22% of female carriers of DMD mutations exhibit clinical symptoms of variable severity. Development of symptoms in DMD mutation carriers without chromosomal rearrangements has been attributed to skewed X-chromosome inactivation (XCI) favouring predominant expression of the DMD mutant allele. However the prognostic use of XCI analysis is controversial. We aimed to evaluate the correlation between X-chromosome inactivation and development of clinical symptoms in a series of symptomatic female carriers of dystrophinopathy. Methods We reviewed the clinical, pathological and genetic features of twenty-four symptomatic carriers covering a wide spectrum of clinical phenotypes. DMD gene analysis was performed using MLPA and whole gene sequencing in blood DNA and muscle cDNA. Blood and muscle DNA was used for X-chromosome inactivation (XCI) analysis thought the AR methylation assay in symptomatic carriers and their female relatives, asymptomatic carriers as well as non-carrier females. Results Symptomatic carriers exhibited 49.2% more skewed XCI profiles than asymptomatic carriers. The extent of XCI skewing in blood tended to increase in line with the severity of muscle symptoms. Skewed XCI patterns were found in at least one first-degree female relative in 78.6% of symptomatic carrier families. No mutations altering XCI in the XIST gene promoter were found. Conclusions Skewed XCI is in many cases familial inherited. The extent of XCI skewing is related to phenotype severity. However, the assessment of XCI by means of the AR methylation assay has a poor prognostic value, probably because the methylation status of the AR gene in muscle may not reflect in all cases the methylation status of the DMD gene.
X-Chromosome Inactivation in Rett Syndrome Human Induced Pluripotent Stem Cells
Lindsay M. Horvath,James Ellis
Frontiers in Psychiatry , 2012, DOI: 10.3389/fpsyt.2012.00024
Abstract: Rett syndrome (RTT) is a neurodevelopmental disorder that affects girls due primarily to heterozygous mutations in the X-linked gene encoding methyl-CpG binding protein 2 (MECP2). Random X-chromosome inactivation (XCI) results in cellular mosaicism in which some cells express wild-type (WT) MECP2 while other cells express mutant MECP2. The generation of patient-specific human induced pluripotent stem cells (hiPSCs) facilitates the production of RTT-hiPSC-derived neurons in vitro to investigate disease mechanisms and identify novel drug treatments. The generation of RTT-hiPSCs has been reported by many laboratories, however, the XCI status of RTT-hiPSCs has been inconsistent. Some report RTT-hiPSCs retain the inactive X-chromosome (post-XCI) of the founder somatic cell allowing isogenic RTT-hiPSCs that express only the WT or mutant MECP2 allele to be isolated from the same patient. Post-XCI RTT-hiPSCs-derived neurons retain this allele-specific expression pattern of WT or mutant MECP2. Conversely, others report RTT-hiPSCs in which the inactive X-chromosome of the founder somatic cell reactivates (pre-XCI) upon reprogramming into RTT-hiPSCs. Pre-XCI RTT-hiPSC-derived neurons exhibit random XCI resulting in cellular mosaicism with respect to WT and mutant MECP2 expression. Here we review and attempt to interpret the inconsistencies in XCI status of RTT-hiPSCs generated to date by comparison to other pluripotent systems in vitro and in vivo and the methods used to analyze XCI. Finally, we discuss the relative strengths and weaknesses of post- and pre-XCI hiPSCs in the context of RTT, and other X-linked and autosomal disorders for translational medicine.
Analysis of Linkage for Ten X-STR Markers in a Rio de Janeiro (Brazil) Three-Generation Family Sample  [PDF]
Roberto Chan, Elizeu Fagundes de Carvalho, Juliana Gozi de Aquino, Dayse Aparecida da Silva, Gisele L？bo-Hajdu
Open Journal of Genetics (OJGen) , 2014, DOI: 10.4236/ojgen.2014.43025
Abstract:

Recently, typing of polymorphisms on the X chromosome has become a standard technique in forensic genetics and a growing number of short tandem repeats (STR) has been established in this chromosome related to genetic population studies. Knowledge of marker recombination is very important especially when the X chromosome typing is used in forensic kinship analysis. It is known that the meiotic recombination is not a simple function of the physical distance between segments of the DNA but the recombination events between them tend to be clustered at special regions of the chromosome. Information on the rate of recombination among markers can be gathered by studying families through several generations. In this work we have typed DNA samples of pedigree consisting of nineteen families in Rio de Janeiro, constituted of grandfather, mother and grandson, and in some cases grandmother and aunt, and reported the recombination of 10 STR markers of the X chromosome. The study of the linkage analysis using the LOD score has shown that the marker pairs DXS8378-DXS7423, DXS7132-DXS9898, DXS7132-GATA172D05 DXS9898-DXS7133 and DXS6809-DXS7133 are not transmitted in a random way, during a recombination event.

Fine-scale evolutionary genetic insights into Anopheles gambiae X-chromosome  [PDF]
Hemlata Srivastava, Jyotsana Dixit, Aditya P. Dash, Aparup Das
Journal of Biomedical Science and Engineering (JBiSE) , 2009, DOI: 10.4236/jbise.2009.25045
Abstract: Understanding the genetic architecture of indi-vidual taxa of medical importance is the first step for designing disease preventive strategies. To understand the genetic details and evolu-tionary perspective of the model malaria vector, Anopheles gambiae and to use the information in other species of local importance, we scanned the published X-chromosome se-quence for detail characterization and obtain evolutionary status of different genes. The te-locentric X-chromosome contains 106 genes of known functions and 982 novel genes. Majori-ties of both the known and novel genes are with introns. The known genes are strictly biased towards less number of introns; about half of the total known genes have only one or two in-trons. The extreme sized (either long or short) genes were found to be most prevalent (58% short and 23% large). Statistically significant positive correlations between gene length and intron length as well as with intron number and intron length were obtained signifying the role of introns in contributing to the overall size of the known genes of X-chromosome in An. gam-biae. We compared each individual gene of An. gambiae with 33 other taxa having whole ge-nome sequence information. In general, the mosquito Aedes aegypti was found to be ge-netically closest and the yeast Saccharomyces cerevisiae as most distant taxa to An. gambiae. Further, only about a quarter of the known genes of X-chromosome were unique to An. gambiae and majorities have orthologs in dif-ferent taxa. A phylogenetic tree was constructed based on a single gene found to be highly orthologous across all the 34 taxa. Evolutionary relationships among 13 different taxa were in-ferred which corroborate the previous and pre-sent findings on genetic relationships across various taxa.
Late-replicating X-chromosome: replication patterns in mammalian females
Tunin, Karen;Otto, Priscila Guimar？es;
Genetics and Molecular Biology , 2002, DOI: 10.1590/S1415-47572002000300009
Abstract: the gtg-banding and 5-brdu incorporation patterns of the late-replicating x-chromosome were studied in female dogs and cattle, and compared to human female patterns. the replication patterns of the short arm of the x-chromosomes did not show any difference between human, dog and cattle females. as to the long arm, some bands showed differences among the three studied species regarding the replication kinetics pattern. these differences were observed in a restricted region of the x-chromosome, delimited by xq11 ？ q25 in humans, by xq1 ？ q8 in dogs, and by xq12 ？ q32 in cattle. in an attempt to find out if these differences in the replication kinetics could be a reflection of differences in the localization of genes in that region of the x-chromosome, we used the probe for the human androgen receptor gene (ar) localized at xq12, which is in the region where we observed differences among the three studied species. we did not, however, observe hybridization signals. our study goes on, using other human probes for genes located in the region xq11 ？ xq25.
Late-replicating X-chromosome: replication patterns in mammalian females
Tunin Karen,Otto Priscila Guimar？es
Genetics and Molecular Biology , 2002,
Abstract: The GTG-banding and 5-BrdU incorporation patterns of the late-replicating X-chromosome were studied in female dogs and cattle, and compared to human female patterns. The replication patterns of the short arm of the X-chromosomes did not show any difference between human, dog and cattle females. As to the long arm, some bands showed differences among the three studied species regarding the replication kinetics pattern. These differences were observed in a restricted region of the X-chromosome, delimited by Xq11 -> q25 in humans, by Xq1 -> q8 in dogs, and by Xq12 -> q32 in cattle. In an attempt to find out if these differences in the replication kinetics could be a reflection of differences in the localization of genes in that region of the X-chromosome, we used the probe for the human androgen receptor gene (AR) localized at Xq12, which is in the region where we observed differences among the three studied species. We did not, however, observe hybridization signals. Our study goes on, using other human probes for genes located in the region Xq11 -> Xq25.
A Study on the Genetic Inheritance of Ankyloglossia Based on Pedigree Analysis
Soo-Hyung Han,Min-Cheol Kim1,Yun-Seok Choi,Jin-Soo Lim
Archives of Plastic Surgery , 2012, DOI: http://dx.doi.org/10.5999/aps.2012.39.4.329
Abstract: Background Ankyloglossia or tongue-tie is a congenital anomaly characterized by an abnormallyshort lingual frenum. Its prevalence in the newborn population is approximately 4%. Its modeof inheritance has been studied in some articles, but no conclusion has been established. Also,no relevant report has been published in Korea. This study was conducted to elucidate thegenetic inheritance of ankyloglossia via pedigree analysis.Methods In this study, 149 patients with no other congenital anomaly who underwentfrenuloplasty between March 2001 and March 2010 were studied. Pedigrees were made viapre- or post-operative history taking, and patients with uncertain histories were excluded.In the patient group that showed a hereditary nature, the male-to-female ratio, inheritancerate, and pattern of inheritance were investigated.Results One hundred (67.11%) of the patients were male and 49 (32.89%) were female(male-female ratio=2.04:1). Ninety-one (61.07%) patients reported no other relative withankyloglossia, and 58 (38.93%) patients had a relative with this disease. The inheritance ratewas 20.69% in the 58 cases with a hereditary nature. In the group with no family history ofankyloglossia, the male-female ratio was 3.79:1, which significantly differed from that ofthe group with a family history of ankyloglossia. X-chromosome mediated inheritance andvariation in the gene expression was revealed in the pedigree drawn for the groups withhereditary ankyloglossia.Conclusions Ankyloglossia has a significant hereditary nature. Our data suggest X-linkedinheritance. This study with 149 patients, the first in Korea, showed X-linked inheritance inpatients with a sole anomaly.
Turner Syndrome
Ramachandran Sudarshan,G. Sree Vijayabala,KS Prem Kumar
Arsiv Kaynak Tarama Dergisi , 2012,
Abstract: Turner syndrome is a genetic disorder that affects mostly females. Affected females have characteristic features such as short stature, premature ovarian failure, and several other features. Oral manifestations of this condition are not much discussed in the literature. But reported literature includes teeth, palate, periodontal and salivary changes. So the aim of this review is to illustrate the general manifestations, and especially the oral manifestations of Turner syndrome and evaluate their possible management. [Archives Medical Review Journal 2012; 21(4.000): 246-252]
Regions of XY homology in the pig X chromosome and the boundary of the pseudoautosomal region
Skinner Benjamin M,Lachani Kim,Sargent Carole A,Affara Nabeel A
BMC Genetics , 2013, DOI: 10.1186/1471-2156-14-3
Abstract: Background Sex chromosomes are subject to evolutionary pressures distinct from the remainder of the genome, shaping their structure and sequence content. We are interested in the sex chromosomes of domestic pigs (Sus scrofa), how their structure and gene content compares and contrasts with other mammalian species, and the role of sex-linked genes in fertility. This requires an understanding of the XY-homologous sequence on these chromosomes. To this end, we performed microarray-based comparative genomic hybridisation (array-CGH) with male and female Duroc genomic DNA on a pig X-chromosome BAC tiling-path microarray. Putative XY-homologous BACs from regions of interest were subsequently FISH mapped. Results We show that the porcine PAR is approximately 6.5-6.9 Mb at the beginning of the short arm of the X, with gene content reflective of the artiodactyl common ancestor. Our array-CGH data also shows an XY-homologous region close to the end of the X long arm, spanning three X BACs. These BACs were FISH mapped, and paint the entire long arm of SSCY. Further clones of interest revealed X-autosomal homology or regions containing repetitive content. Conclusions This study has identified regions of XY homology in the pig genome, and defined the boundary of the PAR on the X chromosome. This adds to our understanding of the evolution of the sex chromosomes in different mammalian lineages, and will prove valuable for future comparative genomic work in suids and for the construction and annotation of the genome sequence for the sex chromosomes. Our finding that the SSCYq repetitive content has corresponding sequence on the X chromosome gives further insight into structure of SSCY, and suggests further functionally important sequences remain to be discovered on the X and Y.
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