The appearance of mammalian-specific skin features was a key evolutionary event contributing for the elaboration of physiological processes such as thermoregulation, adequate hydration, locomotion, and inflammation. Skin inflammatory and autoimmune processes engage a population of skin-infiltrating T cells expressing a specific C-C chemokine receptor (CCR10) which interacts with an epidermal CC chemokine, the skin-specific C-C motif chemokine ligand 27 (CCL27). CCL27 is selectively produced in the skin by keratinocytes, particularly upon inflammation, mediating the adhesion and homing of skin-infiltrating T cells. Here, we examined the evolution and coding condition of Ccl27 in 112 placental mammalian species. Our findings reveal that a number of open reading frame inactivation events such as insertions, deletions, and start and stop codon mutations independently occurred in Cetacea, Pholidota, Sirenia, Chiroptera, and Rodentia, totalizing 18 species. The diverse habitat settings and lifestyles of Ccl27-eroded lineages probably implied distinct evolutionary triggers rendering this gene unessential. For example, in Cetacea, the rapid renewal of skin layers minimizes the need for an elaborate inflammatory mechanism, mirrored by the absence of epidermal scabs. Our findings suggest that the convergent and independent loss of Ccl27 in mammalian evolution concurred with unique adaptive roads for skin physiology.

中文翻译：

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在哺乳动物进化中皮肤特异性CC基序趋化因子配体27的收敛失活。

哺乳动物特有的皮肤特征的出现是关键的进化事件，有助于阐明生理过程，例如温度调节，适当的水合作用，运动和炎症。皮肤炎性和自身免疫过程与表达特定CC趋化因子受体（CCR10）的皮肤浸润T细胞结合，该受体与表皮CC趋化因子，皮肤特异性CC基序趋化因子配体27（CCL27）相互作用。CCL27由角质形成细胞在皮肤中选择性产生，尤其是在炎症时，介导皮肤浸润性T细胞的粘附和归巢。在这里，我们检查了112个胎盘哺乳动物物种中Ccl27的进化和编码条件。我们的发现揭示了许多开放阅读框失活事件，例如插入，缺失，和起始和终止密码子突变分别发生在鲸类，凤尾科，西里尼亚，翼手目和啮齿动物中，共有18种。Ccl27侵蚀的血统的不同的栖息地设置和生活方式可能暗示着独特的进化触发因素，使该基因变得不必要。例如，在鲸类中，皮肤层的快速更新将对精细炎症机制的需求降至最低，这与不存在表皮sc疮的情况相吻合。我们的发现表明，哺乳动物进化过程中Ccl27的收敛和独立丧失与皮肤生理学的独特适应性道路一致。例如，在鲸类中，皮肤表皮的快速更新使对精细炎症机制的需求降至最低，这与不存在表皮sc疮的情况相映成趣。我们的发现表明，哺乳动物进化过程中Ccl27的收敛和独立丧失与皮肤生理学的独特适应性道路一致。例如，在鲸类中，皮肤表皮的快速更新使对精细炎症机制的需求降至最低，这与不存在表皮sc疮的情况相映成趣。我们的发现表明，哺乳动物进化过程中Ccl27的收敛和独立丧失与皮肤生理学的独特适应性道路一致。