@article{73a47de0ee2a11dd84b0000ea68e967b,
title = "Neo-sex chromosomes in the black muntjac recapitulate incipient evolution of mammalian sex chromosomes",
abstract = "BACKGROUND: The regular mammalian X and Y chromosomes diverged from each other at least 166 to 148 million years ago, leaving few traces of their early evolution, including degeneration of the Y chromosome and evolution of dosage compensation. RESULTS: We studied the intriguing case of black muntjac, in which a recent X-autosome fusion and a subsequent large autosomal inversion within just the past 0.5 million years have led to inheritance patterns identical to the traditional X-Y (neo-sex chromosomes). We compared patterns of genome evolution in 35-kilobase noncoding regions and 23 gene pairs on the homologous neo-sex chromosomes. We found that neo-Y alleles have accumulated more mutations, comprising a wide variety of mutation types, which indicates cessation of recombination and is consistent with an ongoing neo-Y degeneration process. Putative deleterious mutations were observed in coding regions of eight investigated genes as well as cis-regulatory regions of two housekeeping genes. In vivo assays characterized a neo-Y insertion in the promoter of the CLTC gene that causes a significant reduction in allelic expression. A neo-Y-linked deletion in the 3'-untranslated region of gene SNX22 abolished a microRNA target site. Finally, expression analyses revealed complex patterns of expression divergence between neo-Y and neo-X alleles. CONCLUSION: The nascent neo-sex chromosome system of black muntjacs is a valuable model in which to study the evolution of sex chromosomes in mammals. Our results illustrate the degeneration scenarios in various genomic regions. Of particular importance, we report--for the first time--that regulatory mutations were probably able to accelerate the degeneration process of Y and contribute to further evolution of dosage compensation.",
keywords = "Animals, Evolution, Molecular, Female, Male, Muntjacs, Mutation, Transcription, Genetic, X Chromosome, Y Chromosome",
author = "Qi Zhou and Jun Wang and Ling Huang and Wenhui Nie and Jinhuan Wang and Yan Liu and Xiangyi Zhao and Fengtang Yang and Wen Wang",
year = "2008",
month = jan,
day = "1",
doi = "10.1186/gb-2008-9-6-r98",
language = "English",
volume = "9",
pages = "R98",
journal = "Genome Biology",
issn = "1474-760X",
publisher = "BioMed Central",
number = "6",
}