Bellott Daniel W, Skaletsky Helen, Hughes Jennifer F, Brown Laura G, Pyntikova Tatyana, Cho Ting-Jan, Koutseva Natalia, Zaghlul Sara, Kizghin Dilziba, Mendoza Mayra, Raudsepp Terje, Dugan Shannon, Khan Ziad, Wang Qiaoyan, Watt Jennifer, Worley Kim C, Scherer Steven, Muzny Donna M, Gibbs Richard A, Page David C
Whitehead Institute, Cambridge, Massachusetts 02142, USA.
Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts 02142, USA.
bioRxiv. 2025 Jun 1:2025.05.28.656580. doi: 10.1101/2025.05.28.656580.
Crossing-over between Chr X and Chr Y was first observed 90 years ago, in the brown rat, . However, the sequence of the rat pseudoautosomal region (PAR) has remained a mystery. We produced a near-complete sequence of Chr Y from the SHR strain, along with nearly a megabase of sequence from both telomeres of Chr X. Both telomeric ends of Chr Y display extensive homology to Chr X, but no homology to the ancestral PAR of placental mammals. Using rat Y BACs probes for FISH on meiotic cells, we show that pairing almost always occurs between the tips of Yq and Xp, which are virtually identical in nucleotide sequence, but contain no protein-coding genes. Homology at the other ends of Chr X and Chr Y is likely the result of a recent transposition of five genes from Xq to Yp. These sequences are only 99.5% identical and pair infrequently, but show signs that it may have been pseudoautosomal in the ancestor of the rat genus. The rat Chr Y sequence presents opportunities for experimental studies of meiotic phenomena in a tractable model organism. The short PAR, with a correspondingly high recombination rate, represents a unique substrate for molecular studies of crossing-over. Likewise, the absence of extensively co-amplified testis gene families on the rat X and Y suggests they might serve as control for the intense competition between selfish elements that completely remodeled the mouse sex chromosomes.
90年前，在褐鼠中首次观察到X染色体与Y染色体之间的交叉现象。然而，大鼠假常染色体区域（PAR）的序列一直是个谜。我们生成了SHR品系Y染色体的近乎完整的序列，以及X染色体两个端粒近1兆碱基的序列。Y染色体的两个端粒末端与X染色体显示出广泛的同源性，但与胎盘哺乳动物的祖先PAR没有同源性。使用大鼠Y BAC探针在减数分裂细胞上进行荧光原位杂交，我们发现配对几乎总是发生在Yq和Xp的末端之间，它们在核苷酸序列上几乎相同，但不包含蛋白质编码基因。X染色体和Y染色体另一端的同源性可能是最近五个基因从Xq转座到Yp的结果。这些序列只有99.5%的同一性，配对很少见，但显示出在大鼠属的祖先中可能是假常染色体的迹象。大鼠Y染色体序列为在一个易于处理的模式生物中对减数分裂现象进行实验研究提供了机会。短的PAR具有相应高的重组率，是交叉分子研究的独特底物。同样，大鼠X染色体和Y染色体上没有广泛共扩增的睾丸基因家族，这表明它们可能作为自私元件之间激烈竞争的对照，这些自私元件完全重塑了小鼠性染色体。
