LaFlamme S E, Jamrich M, Richter K, Sargent T D, Dawid I B
Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, Maryland 20892.
Genes Dev. 1988 Jul;2(7):853-62. doi: 10.1101/gad.2.7.853.
Screening of a cDNA library from neurula stage Xenopus laevis for notochord-specific sequences led to the isolation of a cDNA clone, XK endo B (Xenopus keratin endo B), which encodes a nonepidermal type I keratin. In situ and Northern blot hybridizations indicate that expression of XK endo B RNA is concentrated in the notochord, whereas expression in the endoderm is 5-10 times lower. XK endo B mRNA is present in the oocyte and increases from late gastrula. Accumulation peaks by late neurula and is greatly reduced by the tadpole stage; in the adult, a low level of XK endo B RNA is present in the liver. XK endo B shows sequence homology to mouse endo B; genomic Southern blots show that XK endo B is the most similar sequence to mouse endo B in the Xenopus genome, and vice versa, indicating that XK endo B and mouse endo B are homologs. The use of endo B as a marker and the germ layer derivation of the notochord are discussed in light of these results.
从非洲爪蟾神经胚期的cDNA文库中筛选脊索特异性序列，得到一个cDNA克隆，即XK内B（非洲爪蟾角蛋白内B），它编码一种非表皮型I角蛋白。原位杂交和Northern印迹杂交表明，XK内B RNA的表达集中在脊索中，而在内胚层中的表达则低5至10倍。XK内B mRNA存在于卵母细胞中，从原肠胚后期开始增加。在神经胚后期积累达到峰值，到蝌蚪期则大幅减少；在成体中，肝脏中存在低水平的XK内B RNA。XK内B与小鼠内B显示出序列同源性；基因组Southern印迹表明，XK内B是非洲爪蟾基因组中与小鼠内B最相似的序列，反之亦然，这表明XK内B和小鼠内B是同源物。根据这些结果，讨论了使用内B作为标记以及脊索的胚层起源。
