Spermatogenic cell specific gene expression in mammals : Enzymes of glycolysis

据报道，糖酵解途径中的几种酶具有生精细胞特异性酶和基因。我们先前报道了生精细胞特异性甘油醛-3-磷酸脱氢酶（mGapd-s）和三个独特的生精细胞特异性己糖激酶I型cDNA的分离（mHk 1-sa、mHk 1-sb和mHk 1-sc）及其在小鼠生精细胞中的表达模式[Mori等，Biol Reprod 46：859- 868，1992; Mori等，Biol Reprod 49：191- 203，1993]。为了进一步分析小鼠Gapd-s和小鼠Hk 1-s基因产物的功能，我们需要克隆人Gapd-s和人HK 1-s（t）基因，并将小鼠和人的Gapd-s和HK 1-s（t）基因序列进行比较。我们克隆了人Gapd-s基因，并鉴定了三种在人睾丸中表达的人己糖激酶I型mRNA（hHK 1-ta，hHK 1-tb和hHK 1-tc）。人GAPD-S的氨基酸序列与小鼠GAPD-S序列有91%的相似性，但与人体细胞GAPD-S序列的相似性仅为71%。（hHK 1-ta、hHK 1-tb和hHK 1-tc）不含孔蛋白结合蛋白（PBD），但它们含有共同的睾丸特异性序列和每个cDNA特有的序列。hHK 1-ta，hHK 1-tb，hHK 1-tc与mHk 1-sa、mHk 1-sb和mHk 1-sc中的一个生精细胞特异性基因序列有一定的同源性，但与基因库中已报道的其它已知基因没有明显的同源性。我们的研究结果表明，缺乏PBD的己糖激酶I型mRNA在其他哺乳动物的睾丸中表达，似乎支持其他人提出的哺乳动物己糖激酶基因进化模型。

Several enzymes in the glycolytic pathway are reported to have permatogenic cell-specific enzymes and genes. We previously reported isolation of spermatogenic cell specific glyceraldehyde-3-phosphate dehydrogenase (mGapd-s) and three unique spermatogenic cell specific hexokinase type I cDNAs (mHk1-sa, mHk1-sb and mHk1-sc) from mouse spermatogenic cell library and their expression patterns in mouse spermatogenic cells [Mori et al. Biol Reprod 46 : 859-868,1992 ; Mori et al. Biol Reprod 49 : 191-203,1993] . In order to analysis of function of gene products of mouse Gapd-s and mouse Hk1-s, we needed the cloning of human Gapd-s and human HK1-s (t) and the comparison of those sequences from mice and humans. We report here the cloning of human Gapd-s and the identification of three unique human hexokinase type I mRNAs (hHK1-ta, hHK1-tb and hHK1-tc) which are expressed in human testis. The amino acids of human GAPD-S have a 91% match with the mouse GAPD-S sequence, but only a 71% similarity to the human somatic GAPD.All three testis specific human hexokinase type I mRNAs (hHK1-ta, hHK1-tb and hHK1-tc) don't contain porin-binding protein (PBD) , but they contain a common testis-specific sequence and a sequence unique to each cDNA.This common testis-specific sequence in mRNAs of hHK1-ta, hHK1-tb, and hHK1-tc has some homology with a common spermatogenic cell-specific sequence in those of mHk1-sa, mHk1-sb and mHk1-sc, and but no significant homology with other known genes reported in GENE BANK in any species. Our findings show that hexokinase type I mRNAs lacking PBD are expressed in testes from other mammals, and appear to support a model proposed by others for hexokinase gene evolution in mammals.