Harrison Gavan A, Young Lauren J, Watson Catherine M, Miska Katarzyna B, Miller Robert D, Deane Elizabeth M
School of Science, Food and Horticulture, BCRI Building, University of Western Sydney, Locked bag 1797, Penrith South DC, NSW 1797, Australia.
Cytokine. 2003 Feb 7;21(3):105-19. doi: 10.1016/s1043-4666(03)00029-2.
Sequence data for type I interferons (IFNs) have previously only been available for birds and eutherian ('placental') mammals, but not for the other two groups of extant mammals, the marsupials and monotremes. This has left a large gap in our knowledge of the evolutionary and functional relationships of what is a complex gene family in eutherians. In this study, a PCR-based survey of type I IFN genes from a marsupial, the tammar wallaby (Macropus eugenii), and a monotreme, the short-beaked echidna (Tachyglossus aculeatus), was conducted. Along with Southern blot and phylogenetic analysis, this revealed a large number of type I IFN genes for the wallaby, rivalling that of eutherians, but relatively few type I IFN genes in the echidna. The wallaby genes include both IFNA and IFNB orthologues, indicating that the gene duplication leading to these subtypes occurred prior to the divergence of marsupials and eutherians some 130 million years ago. Results from this study support the idea that the expansion of type I IFN gene complexity in mammals coincides with a concomitant expansion in the functionality of these molecules. For example, this expansion in complexity may have, at least partially, facilitated the evolution of viviparity in marsupials and eutherians. Other evolutionary aspects of these sequences are also discussed.
I型干扰素（IFNs）的序列数据此前仅在鸟类和真兽亚纲（“有胎盘的”）哺乳动物中可得，而在现存的另外两类哺乳动物——有袋类动物和单孔目动物中却没有。这使得我们对于真兽亚纲中这个复杂基因家族的进化和功能关系的了解存在很大空白。在本研究中，对一种有袋类动物——帚尾袋鼩（Macropus eugenii）和一种单孔目动物——短吻针鼹（Tachyglossus aculeatus）的I型干扰素基因进行了基于聚合酶链反应（PCR）的调查。结合Southern印迹法和系统发育分析，结果显示帚尾袋鼩拥有大量的I型干扰素基因，数量与真兽亚纲动物相当，但短吻针鼹的I型干扰素基因相对较少。帚尾袋鼩的基因包括IFNA和IFNB直系同源基因，这表明导致这些亚型的基因复制发生在约1.3亿年前有袋类动物和真兽亚纲动物分化之前。本研究结果支持这样一种观点，即哺乳动物中I型干扰素基因复杂性的扩展与这些分子功能的相应扩展是一致的。例如，这种复杂性的扩展可能至少部分地促进了有袋类动物和真兽亚纲动物胎生的进化。还讨论了这些序列的其他进化方面。
