Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27514
Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27514.
Genetics. 2019 Jun;212(2):469-487. doi: 10.1534/genetics.119.302232. Epub 2019 Apr 26.
Faithful segregation of homologous chromosomes at meiosis requires pairing and recombination. In taxa with dimorphic sex chromosomes, pairing between them in the heterogametic sex is limited to a narrow interval of residual sequence homology known as the pseudoautosomal region (PAR). Failure to form the obligate crossover in the PAR is associated with male infertility in house mice () and humans. Yet despite this apparent functional constraint, the boundary and organization of the PAR is highly variable in mammals, and even between subspecies of mice. Here, we estimate the genetic map in a previously documented expansion of the PAR in the subspecies and show that the local recombination rate is 100-fold higher than the autosomal background. We identify an independent shift in the PAR boundary in the subspecies and show that it involves a complex rearrangement, but still recombines in heterozygous males. Finally, we demonstrate pervasive copy-number variation at the PAR boundary in wild populations of , , and Our results suggest that the intensity of recombination activity in the PAR, coupled with relatively weak constraints on its sequence, permit the generation and maintenance of unusual levels of polymorphism in the population of unknown functional significance.
减数分裂中同源染色体的正确分离需要配对和重组。在具有二态性性染色体的分类单元中，它们在异型性别的配对仅限于称为假常染色体区（PAR）的残余序列同源性的狭窄间隔内。PAR 中必需的交叉形成失败与雄性不育有关小家鼠（）和人类。尽管存在这种明显的功能限制，但在哺乳动物中，甚至在小鼠亚种之间，PAR 的边界和组织都具有高度的可变性。在这里，我们估计了在先前记录的 PAR 扩展中的遗传图谱亚种并且表明局部重组率比常染色体背景高 100 倍。我们确定了亚种中 PAR 边界的独立转移，并且表明它涉及复杂的重排，但在杂合雄性中仍能重组。最后，我们证明了在亚种的 PAR 边界处存在普遍的拷贝数变异野生种群和。我们的研究结果表明，PAR 中重组活性的强度，再加上其序列的相对较弱的限制，允许在未知功能意义的种群中产生和维持异常水平的多态性。
