Massive expansion of sex-specific SNPs, transposon-related elements, and neocentromere formation shape the young W-chromosome from the mosquitofish Gambusia affinis.
Neocentromere
SNP accumulation
Sex chromosome evolution
Transposable element
W-specific non-coding gonadal expression
ZZ/ZW sex chromosomes
Journal
BMC biology
ISSN: 1741-7007
Titre abrégé: BMC Biol
Pays: England
ID NLM: 101190720
Informations de publication
Date de publication:
15 05 2023
15 05 2023
Historique:
received:
09
12
2022
accepted:
27
04
2023
medline:
17
5
2023
pubmed:
16
5
2023
entrez:
15
5
2023
Statut:
epublish
Résumé
The Western mosquitofish, Gambusia affinis, is a model for sex chromosome organization and evolution of female heterogamety. We previously identified a G. affinis female-specific marker, orthologous to the aminomethyl transferase (amt) gene of the related platyfish (Xiphophorus maculatus). Here, we have analyzed the structure and differentiation of the G. affinis W-chromosome, using a cytogenomics and bioinformatics approach. The long arm of the G. affinis W-chromosome (Wq) is highly enriched in dispersed repetitive sequences, but neither heterochromatic nor epigenetically silenced by hypermethylation. In line with this, Wq sequences are highly transcribed, including an active nucleolus organizing region (NOR). Female-specific SNPs and evolutionary young transposable elements were highly enriched and dispersed along the W-chromosome long arm, suggesting constrained recombination. Wq copy number expanded elements also include female-specific transcribed sequences from the amt locus with homology to TE. Collectively, the G. affinis W-chromosome is actively differentiating by sex-specific copy number expansion of transcribed TE-related elements, but not (yet) by extensive sequence divergence or gene decay. The G. affinis W-chromosome exhibits characteristic genomic properties of an evolutionary young sex chromosome. Strikingly, the observed sex-specific changes in the genomic landscape are confined to the W long arm, which is separated from the rest of the W-chromosome by a neocentromere acquired during sex chromosome evolution and may thus have become functionally insulated. In contrast, W short arm sequences were apparently shielded from repeat-driven differentiation, retained Z-chromosome like genomic features, and may have preserved pseudo-autosomal properties.
Sections du résumé
BACKGROUND
The Western mosquitofish, Gambusia affinis, is a model for sex chromosome organization and evolution of female heterogamety. We previously identified a G. affinis female-specific marker, orthologous to the aminomethyl transferase (amt) gene of the related platyfish (Xiphophorus maculatus). Here, we have analyzed the structure and differentiation of the G. affinis W-chromosome, using a cytogenomics and bioinformatics approach.
RESULTS
The long arm of the G. affinis W-chromosome (Wq) is highly enriched in dispersed repetitive sequences, but neither heterochromatic nor epigenetically silenced by hypermethylation. In line with this, Wq sequences are highly transcribed, including an active nucleolus organizing region (NOR). Female-specific SNPs and evolutionary young transposable elements were highly enriched and dispersed along the W-chromosome long arm, suggesting constrained recombination. Wq copy number expanded elements also include female-specific transcribed sequences from the amt locus with homology to TE. Collectively, the G. affinis W-chromosome is actively differentiating by sex-specific copy number expansion of transcribed TE-related elements, but not (yet) by extensive sequence divergence or gene decay.
CONCLUSIONS
The G. affinis W-chromosome exhibits characteristic genomic properties of an evolutionary young sex chromosome. Strikingly, the observed sex-specific changes in the genomic landscape are confined to the W long arm, which is separated from the rest of the W-chromosome by a neocentromere acquired during sex chromosome evolution and may thus have become functionally insulated. In contrast, W short arm sequences were apparently shielded from repeat-driven differentiation, retained Z-chromosome like genomic features, and may have preserved pseudo-autosomal properties.
Identifiants
pubmed: 37189152
doi: 10.1186/s12915-023-01607-0
pii: 10.1186/s12915-023-01607-0
pmc: PMC10186657
doi:
Substances chimiques
DNA Transposable Elements
0
Types de publication
Journal Article
Research Support, Non-U.S. Gov't
Langues
eng
Sous-ensembles de citation
IM
Pagination
109Informations de copyright
© 2023. The Author(s).
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