Savtchenko E S, Schiff T A, Jiang C K, Freedberg I M, Blumenberg M
Department of Dermatology, New York University Medical Center, NY 10016.
Am J Hum Genet. 1988 Nov;43(5):630-7.
Analysis of the cytoskeletal components of early murine embryos has detected expression of two keratin proteins, K#8 and K#18, at the 4-8-cell stage. Comparable data for human embryos do not exist, although several processed pseudogenes corresponding to K#8 and K#18 have been discovered in the human genome. Because only genes that are expressed in pre-germ-line and germ-line cells can give rise to processed pseudogenes, the existence of human K#8 and K#18 processed pseudogenes is prima facie evidence for expression of keratins K#8 and K#18 in the early human embryo. We have cloned and determined the complete sequence of a processed pseudogene corresponding to another acidic human keratin. Comparison of its sequence with known sequences of other mammalian keratins indicates that the pseudogene arose from a reverse transcript of a correctly initiated and terminated functional human K#19 gene. This implies expression of K#19 keratin in addition to K#8 and K#18 in the early human embryo. We have proposed previously that K#19 evolved specifically to redress unbalanced production of various basic keratins, and our current evidence, that it is expressed at an early stage of development, implies that K#19 may fulfill this same role during human embryogenesis.
对早期小鼠胚胎细胞骨架成分的分析检测到，在4-8细胞阶段有两种角蛋白K#8和K#18表达。虽然在人类基因组中已发现了几个与K#8和K#18相对应的加工假基因，但关于人类胚胎的类似数据并不存在。由于只有在生殖系前体细胞和生殖系细胞中表达的基因才能产生加工假基因，人类K#8和K#18加工假基因的存在初步证明了角蛋白K#8和K#18在早期人类胚胎中的表达。我们已经克隆并确定了一个与另一种酸性人类角蛋白相对应的加工假基因的完整序列。将其序列与其他哺乳动物角蛋白的已知序列进行比较表明，该假基因源自一个起始和终止均正确的功能性人类K#19基因的逆转录产物。这意味着除了K#8和K#18之外，K#19角蛋白在早期人类胚胎中也有表达。我们之前曾提出，K#19是为了纠正各种碱性角蛋白的不均衡产生而专门进化的，而我们目前关于它在发育早期表达的证据表明，K#19在人类胚胎发生过程中可能也发挥着同样作用。
