美国加州大学河滨分校Polly Campbell研究小组揭示缓行田鼠的性染色体转变和雄性X染色体的起源。相关论文于2021年5月7日发表于国际学术期刊《科学》。
据研究人员介绍，哺乳动物的性染色体系统（XX雌性/XY雄性）是古老且高度保守的。缓行田鼠（Microtus oregoni）的性染色体核型代表了一个长期存在的异常，其X染色体在雌性中不成对（X0），并且仅由母体传播。
研究人员获得了一个高度连续的雄性基因组装配体，以??及两个性别的短读基因组和转录组。研究人员表明，缓行田鼠已经失去了一个独立分离的Y染色体，而雄性特定的性染色体是第二条X染色体，与母体传播的X染色体在很大程度上同源。母体遗传的和雄性特定的性染色体都携带祖先的片段Y染色体。
这种最近转变的性染色体系统的后果包括：在雄性特异性X上发生Y样变性和基因扩增，在雌性中祖先Y连锁基因的表达以及在雄性体细胞中雄性特异性染色体的X失活。缓行田鼠的基因组阐明了影响哺乳动物性染色体基因内容和剂量的过程，并举例说明了古代性染色体系统中罕见的可塑性案例。
附：英文原文
Title: Sex chromosome transformation and the origin of a male-specific X chromosome in the creeping vole
Author: Matthew B. Couger, Scott W. Roy, Noelle Anderson, Landen Gozashti, Stacy Pirro, Lindsay S. Millward, Michelle Kim, Duncan Kilburn, Kelvin J. Liu, Todd M. Wilson, Clinton W. Epps, Laurie Dizney, Luis A. Ruedas, Polly Campbell
Issue&Volume: 2021/05/07
Abstract: The mammalian sex chromosome system (XX female/XY male) is ancient and highly conserved. The sex chromosome karyotype of the creeping vole (Microtus oregoni) represents a long-standing anomaly, with an X chromosome that is unpaired in females (X0) and exclusively maternally transmitted. We produced a highly contiguous male genome assembly, together with short-read genomes and transcriptomes for both sexes. We show that M. oregoni has lost an independently segregating Y chromosome and that the male-specific sex chromosome is a second X chromosome that is largely homologous to the maternally transmitted X. Both maternally inherited and male-specific sex chromosomes carry fragments of the ancestral Y chromosome. Consequences of this recently transformed sex chromosome system include Y-like degeneration and gene amplification on the male-specific X, expression of ancestral Y-linked genes in females, and X inactivation of the male-specific chromosome in male somatic cells. The genome of M. oregoni elucidates the processes that shape the gene content and dosage of mammalian sex chromosomes and exemplifies a rare case of plasticity in an ancient sex chromosome system.
DOI: 10.1126/science.abg7019
Source: https://science.sciencemag.org/content/372/6542/592