Acosta M J, Romero-Fernández I, Sánchez A, Marchal J A
Departamento de Biología Experimental, Facultad de Ciencias Experimentales, Universidad de Jaén, Jaén, Spain.
Cytogenet Genome Res. 2011;132(1-2):47-54. doi: 10.1159/000318012. Epub 2010 Jul 30.
Sex chromosome evolution in mammals has been extensively investigated through chromosome-painting analyses. In some rodent species from the subfamily Arvicolinae the sex chromosomes contain remarkable features such as giant size, a consequence of heterochromatic enlargement, or asynaptic behaviour during male meiosis. Here, we have made a comparative study of the sex chromosomes in 6 arvicolid species using different probes from the X and Y chromosomes of 3 species, in order to gain knowledge about intra- or interspecific preservation of euchromatic regions. Our results clearly reveal poor conservation of the euchromatic region of the Y chromosome within these species, while the euchromatin on the X chromosome is extremely well preserved. Furthermore, we detected no clear correlation between the synaptic/asynaptic behaviour of the sex chromosomes, and the presence or absence of sequence homology within their euchromatic regions. Notably, our study has shown a new relationship between the giant sex chromosomes of 2 species, Microtus agrestis and Microtus cabrerae, that is, both X and Y share a novel region of common sequences in the euchromatin that is not present in the other species analysed. This interspecific euchromatic conservation, limited to the giant sex chromosomes, could point towards a common evolutionary origin for the heterochromatic enlargement process that has characterized the evolution of the sex chromosomes in some arvicolid species.
哺乳动物的性染色体进化已通过染色体涂染分析得到广泛研究。在田鼠亚科的一些啮齿动物物种中，性染色体具有显著特征，如巨大的尺寸，这是异染色质扩增的结果，或者在雄性减数分裂期间表现出不同步行为。在这里，我们使用来自3个物种的X和Y染色体的不同探针，对6种田鼠科物种的性染色体进行了比较研究，以便了解常染色质区域在种内或种间的保留情况。我们的结果清楚地表明，这些物种中Y染色体的常染色质区域保守性较差，而X染色体上的常染色质则保存得非常好。此外，我们没有检测到性染色体的联会/不同步行为与其常染色质区域内序列同源性的有无之间存在明显的相关性。值得注意的是，我们的研究揭示了两个物种，即田鼠和卡氏田鼠的巨大性染色体之间的一种新关系，也就是说，X和Y在常染色质中共享一个其他分析物种中不存在的新的共同序列区域。这种仅限于巨大性染色体的种间常染色质保守性，可能指向一些田鼠科物种性染色体进化所特有的异染色质扩增过程的共同进化起源。
