Yu Miao, Xue Ting, Chen Tiansheng, Fang Jian, Pan Qihua, Deng Yu, Li Lingyu, Chen Kai, Wang Yizhou
College of Fisheries, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Huazhong Agricultural University, Wuhan, People's Republic of China.
College of Fishery, Engineering Technology Research Center of Henan Province for Aquatic Animal Cultivation, Engineering Lab of Henan Province for Aquatic Animal Disease Control, Henan Normal University, Xinxiang, People's Republic of China.
J Exp Zool B Mol Dev Evol. 2017 Dec;328(8):749-759. doi: 10.1002/jez.b.22760. Epub 2017 Aug 23.
The homeodomain transcription factor Nanog plays an essential role in maintaining pluripotency and self-renewal of embryonic stem cells in mammals. However, the evolutionary conservation of its ortholog in teleosts remains elusive. Here we isolated and characterized a Nanog homolog named as Ma-Nanog in blunt-snout bream (Megalobrama amblycephala). The full-length genomic sequence is 3,326 bp in length and consists of four exons encoding a homeodomain protein of 386 amino acid residues. Comparison of protein sequences revealed that Ma-Nanog is highly homologous to those in other teleosts, particularly in the homeodomain region. During embryogenesis, RNA expression of Nanog was only detected in early developmental embryos, predominantly at the blastula stage, which suggested the transcripts were mainly present in pluripotent stem cells. RNA fluorescence in situ hybridization verified that the signal of the transcripts is present in the germ cells. RNA expression was observed in the oogonia and early stage of oocytes in the ovary, or in the spermatogonia, spermatocytes, and spermatids in the testis. Surprisingly, the transcripts were also detected in adult tissues such as in liver by RT-PCR or qRT-PCR. Subcellular localization of the Nanog protein was also verified in nuclei. Taken together, these results suggested that Ma-Nanog is maternally inherited with conserved features, thus can be potentially used as a marker for stem cells in blunt-snout bream.
同源结构域转录因子Nanog在维持哺乳动物胚胎干细胞的多能性和自我更新中起着至关重要的作用。然而，其在硬骨鱼中的直系同源物的进化保守性仍不清楚。在此，我们分离并鉴定了团头鲂（Megalobrama amblycephala）中一个名为Ma-Nanog的Nanog同源物。其全长基因组序列为3326 bp，由四个外显子组成，编码一个含有386个氨基酸残基的同源结构域蛋白。蛋白质序列比较显示，Ma-Nanog与其他硬骨鱼中的同源物高度同源，尤其是在同源结构域区域。在胚胎发育过程中，Nanog的RNA表达仅在早期发育胚胎中检测到，主要在囊胚期，这表明转录本主要存在于多能干细胞中。RNA荧光原位杂交证实转录本信号存在于生殖细胞中。在卵巢的卵原细胞和早期卵母细胞中，或在睾丸的精原细胞、精母细胞和精子细胞中观察到RNA表达。令人惊讶的是，通过RT-PCR或qRT-PCR在肝脏等成体组织中也检测到了转录本。Nanog蛋白的亚细胞定位也在细胞核中得到了证实。综上所述，这些结果表明Ma-Nanog是母系遗传的，具有保守特征，因此有可能作为团头鲂干细胞的标记物。
