The role of meiosis on the evolution of the sex chromosomes

从一对假定的祖先常染色体中了解形成性染色体的进化选择力量是生物学中的一个主要问题(在Khil和Camerini-Otero(2005)Crit中回顾。Biochem牧师。摩尔。比奥尔。40,313)。几年前，有报道称，对线虫和黑腹线虫的全基因组分析表明，男性特有的基因在X染色体上的表达不足，而大约20多个小鼠的精原基因则相反。这款鼠标真的不一样吗？我们对Spo11成年小鼠微阵列数据的分析为睾丸基因的表达提供了一个时间线。我们发现，那些在减数分裂后期细胞中表达的基因，包括大多数富含睾丸的基因，在X染色体上表达不足。然而，早期基因被过度表达。由于先前发表的小鼠数据仅与早期精原基因有关，这些结果与所有数据相一致。此外，我们增加了一块缺失的拼图，提出在大多数生物中，X染色体的去维管化(男性基因的移除)受到男性减数分裂期间性染色体失活的影响(见Reinke(2004)NAT的评论)。吉内。6548人)。实现X染色体重塑的一种方式是通过从X染色体到常染色体的逆转座，而不是在常染色体之间(Shiao等人，在出版社中)。目前，我们没有积极参与这个项目，但计划在明年内开始研究染色体配对如何调节染色体沉默。

Understanding the evolutionary selective forces that fashioned the sex chromosomes from a putative ancestral autosome pair is a major problem in biology (reviewed in Khil and Camerini-Otero (2005) Crit. Rev. Biochem. Mol. Biol. 40, 313). A few years ago it was reported that genome-wide analyses of C. elegans and D. melanogaster revealed that male-specific genes are underrepresented on the X-chromosome whereas the opposite was reported for about 2 dozen mouse spermatogonial genes. Is the mouse really different? Our analysis of the Spo11 adult mice microarray data provided a time line for the expression of testis genes. We found that those genes expressed in cells late in meiosis, including the majority of testis-enriched genes, are underrepresented on the X. However, early genes are overrepresented. Since the previously published mouse data pertained to early spermatogonial genes only, these results reconcile all the data. Furthermore, we added a missing piece of the puzzle by proposing that the demasculinization (removal of male genes) of the X chromosome in most organisms is influenced by inactivation of the sex chromosomes during male meiosis (see commentary in Reinke (2004) Nat. Genet. 6, 548). One manner by which this reshaping of the X chromosome is achieved is by retrotransposition from the X chromosome to autosomes much more frequently than between autosomes (Shiao et al., in press). Presently, we are not actively working on this project bu plan to start within the next year to investigate how chromosome pairing regulates chromosome silencing.