Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK.
J Mol Evol. 2021 Jul;89(6):396-414. doi: 10.1007/s00239-021-10012-6. Epub 2021 Jun 7.
The majority of homeobox genes are highly conserved across animals, but the eutherian-specific ETCHbox genes, embryonically expressed and highly divergent duplicates of CRX, are a notable exception. Here we compare the ETCHbox genes of 34 mammalian species, uncovering dynamic patterns of gene loss and tandem duplication, including the presence of a large tandem array of LEUTX loci in the genome of the European rabbit (Oryctolagus cuniculus). Despite extensive gene gain and loss, all sampled species possess at least two ETCHbox genes, suggesting their collective role is indispensable. We find evidence for positive selection and show that TPRX1 and TPRX2 have been the subject of repeated gene conversion across the Boreoeutheria, homogenising their sequences and preventing divergence, especially in the homeobox region. Together, these results are consistent with a model where mammalian ETCHbox genes are dynamic in evolution due to functional overlap, yet have collective indispensable roles.
大多数同源盒基因在动物中高度保守，但真兽类特异性的 ETCHbox 基因是 CRX 胚胎表达且高度分化的重复基因，是一个显著的例外。在这里，我们比较了 34 种哺乳动物的 ETCHbox 基因，揭示了基因丢失和串联重复的动态模式，包括在欧洲兔（Oryctolagus cuniculus）基因组中存在大量串联的 LEUTX 基因座。尽管广泛的基因获得和丢失，所有采样的物种至少拥有两个 ETCHbox 基因，表明它们的集体作用是不可或缺的。我们发现了正选择的证据，并表明 TPRX1 和 TPRX2 一直是 Boreoeutheria 中基因转换的对象，使它们的序列同质化，防止了分化，尤其是在家盒区。总的来说，这些结果与一个模型一致，即由于功能重叠，哺乳动物的 ETCHbox 基因在进化中是动态的，但具有集体不可或缺的作用。
