The CYP8B1 gene is known to catalyse reactions that determine the ratio of primary bile salts and the loss of this gene has recently been linked to lack of cholic acid in the bile of naked-mole rats, elephants and manatees using forward genomics approaches. We screened the CYP8B1 gene sequence of more than 200 species and test for relaxation of selection along each terminal branch. The need for retaining a functional copy of the CYP8B1 gene is established by the presence of a conserved open reading frame across most species screened in this study. Interestingly, the dietary switch from bovid to cetacean species is accompanied by an exceptional ten amino acid extension at the C-terminal end through a single base frame-shift deletion. We also verify that the coding frame disrupting mutations previously reported in the elephant are correct, are shared by extinct Elephantimorpha species and coincide with the dietary switch to herbivory. Relaxation of selection in the CYP8B1 gene of the wombat (Vombatus ursinus) also corresponds to drastic change in diet. In summary, our forward genomics-based screen of bird and mammal species identifies recurrent changes in the selection landscape of the CYP8B1 gene concomitant with a change in dietary lipid content.

中文翻译：

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鸟类和哺乳动物CYP8B1基因中轻松选择的特征。

已知CYP8B1基因可催化确定初级胆汁盐比率的反应，并且该基因的缺失最近与裸鼠大鼠，大象和海牛的胆汁中胆酸缺乏有关，这是使用正向基因组学方法进行的。我们筛选了超过200种的CYP8B1基因序列，并测试了沿每个末端分支的选择松弛。保留CYP8B1基因功能性拷贝的需要是通过在这项研究中筛选出的大多数物种上存在一个保守的开放阅读框而建立的。有趣的是，从牛至鲸类的饮食转换在C末端通过单个碱基移码缺失而引起了异常的十个氨基酸延伸。我们还验证了先前在大象中报道的破坏编码框架的突变是正确的，被灭绝的象鼻虫物种共有，并且与饮食向草食性转变相吻合。袋熊（Vombatus ursinus）的CYP8B1基因选择的放松也对应于饮食的急剧变化。综上所述，我们基于鸟类和哺乳动物物种的前瞻性基于基因组学的筛查方法可确定CYP8B1基因选择格局中的反复变化，同时伴随饮食中脂质含量的变化。