{"title":"Delineating the W sex chromosome in the clam shrimp, Eulimnadia texana.","authors":"Chathumadavi Ediriweera, Stephen C Weeks","doi":"10.1159/000542284","DOIUrl":null,"url":null,"abstract":"<p><strong>Introduction: </strong>Sex chromosomes have evolved independently across various lineages, often showing convergent degradation of the sex-limited chromosome. While extensively studied in model organisms with ancient sex chromosomal systems, the evolution of early-stage sex chromosomes remains poorly understood. Eulimnadia texana, a freshwater crustacean with a unique androdioecious breeding system (ZZ, ZW, and viable WW genotypes), provides a rare opportunity to study early sex chromosome evolution. This study examines E. texana's W chromosome for evidence of a small localized non-recombining region, characterized by a transposable element (TE) \"hotspot\", low gene density, and low GC content.</p><p><strong>Methods: </strong>Sex-linked markers were mapped onto the W chromosome (Scaffold 1). TEs in the WW genome were identified using RepeatModeler and RepeatMasker. Statistical analyses compared TE distribution between the genome and Scaffold 1, which was then divided into 20 equal-sized \"bins\" for finer-scale statistical analyses. Gene density and GC content were analyzed across these bins.</p><p><strong>Results: </strong>While no significant TE accumulation was found across the entire W chromosome compared to the remaining genome, a specific region (6.6-8.8 Mb, fourth bin) showed significantly higher TE accumulation. This region also exhibited low gene density and low GC content, indicative of reduced recombination.</p><p><strong>Conclusion: </strong>Our findings suggest that E. texana's W chromosome contains a smaller region of crossover suppression, supporting the hypothesis that it is in a proto-sex chromosome in early evolutionary development. This study provides valuable insights into early sex chromosome evolution and establishes E. texana as an ideal model for further investigation of evolutionary processes driving proto-sex chromosome differentiation.</p>","PeriodicalId":11206,"journal":{"name":"Cytogenetic and Genome Research","volume":null,"pages":null},"PeriodicalIF":1.7000,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Cytogenetic and Genome Research","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1159/000542284","RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"CELL BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Introduction: Sex chromosomes have evolved independently across various lineages, often showing convergent degradation of the sex-limited chromosome. While extensively studied in model organisms with ancient sex chromosomal systems, the evolution of early-stage sex chromosomes remains poorly understood. Eulimnadia texana, a freshwater crustacean with a unique androdioecious breeding system (ZZ, ZW, and viable WW genotypes), provides a rare opportunity to study early sex chromosome evolution. This study examines E. texana's W chromosome for evidence of a small localized non-recombining region, characterized by a transposable element (TE) "hotspot", low gene density, and low GC content.
Methods: Sex-linked markers were mapped onto the W chromosome (Scaffold 1). TEs in the WW genome were identified using RepeatModeler and RepeatMasker. Statistical analyses compared TE distribution between the genome and Scaffold 1, which was then divided into 20 equal-sized "bins" for finer-scale statistical analyses. Gene density and GC content were analyzed across these bins.
Results: While no significant TE accumulation was found across the entire W chromosome compared to the remaining genome, a specific region (6.6-8.8 Mb, fourth bin) showed significantly higher TE accumulation. This region also exhibited low gene density and low GC content, indicative of reduced recombination.
Conclusion: Our findings suggest that E. texana's W chromosome contains a smaller region of crossover suppression, supporting the hypothesis that it is in a proto-sex chromosome in early evolutionary development. This study provides valuable insights into early sex chromosome evolution and establishes E. texana as an ideal model for further investigation of evolutionary processes driving proto-sex chromosome differentiation.
期刊介绍：
During the last decades, ''Cytogenetic and Genome Research'' has been the leading forum for original reports and reviews in human and animal cytogenetics, including molecular, clinical and comparative cytogenetics. In recent years, most of its papers have centered on genome research, including gene cloning and sequencing, gene mapping, gene regulation and expression, cancer genetics, comparative genetics, gene linkage and related areas. The journal also publishes key papers on chromosome aberrations in somatic, meiotic and malignant cells. Its scope has expanded to include studies on invertebrate and plant cytogenetics and genomics. Also featured are the vast majority of the reports of the International Workshops on Human Chromosome Mapping, the reports of international human and animal chromosome nomenclature committees, and proceedings of the American and European cytogenetic conferences and other events. In addition to regular issues, the journal has been publishing since 2002 a series of topical issues on a broad variety of themes from cytogenetic and genome research.
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