Tanaka K, Parvinen M, Nigg E A
Department of Molecular Biology, Sciences II, University of Geneva, Switzerland.
Exp Cell Res. 1997 Dec 15;237(2):264-74. doi: 10.1006/excr.1997.3788.
The human protein kinase Nek2 is related to the NIMA cell cycle regulatory kinase of Aspergillus nidulans. Whereas NIMA has been shown to be essential for cell cycle progression into mitosis in this fungus, the function of mammalian Nek2 remains to be elucidated. In this study, we isolated a cDNA coding for a mouse ortholog of human Nek2 and analyzed the expression of this kinase in different organs. RNase protection assays performed on RNAs from mouse adult organs showed very high expression of Nek2 in testis. Lower levels of transcripts were detected in intestine, thymus, and skin, three mitotically active organs, and whole-mount in situ hybridization performed on 10.5-day embryos allowed the detection of Nek2 transcripts in the brain. In situ hybridization analysis of testis sections revealed that the transcription of Nek2 occurred in a stage-specific manner during spermatogenesis. The strongest signals were seen in cells undergoing meiosis, but Nek2 transcripts could also be detected in haploid cells (stage I and II spermatids). Extending these results, in situ hybridization performed on ovary sections revealed strong signals in meiotically active oocytes. In addition, some Nek2 transcription was observed in actively dividing follicle cells surrounding the oocytes and in the oviduct. Finally, indirect immunofluorescence staining of testis sections with Nek2-specific antibodies confirmed that this kinase is highly expressed in spermatocytes and, to a lesser extent, in early spermatids. Taken together, these results indicate that Nek2 may play an important role not only during mitosis but also during meiosis.
人类蛋白激酶Nek2与构巢曲霉的NIMA细胞周期调节激酶相关。虽然已证明NIMA对于该真菌进入有丝分裂的细胞周期进程至关重要，但哺乳动物Nek2的功能仍有待阐明。在本研究中，我们分离出编码人类Nek2小鼠直系同源物的cDNA，并分析了该激酶在不同器官中的表达。对来自成年小鼠器官的RNA进行的核糖核酸酶保护分析显示，Nek2在睾丸中表达非常高。在肠道、胸腺和皮肤这三个有丝分裂活跃的器官中检测到较低水平的转录本，对10.5天胚胎进行的全胚胎原位杂交检测到大脑中有Nek2转录本。睾丸切片的原位杂交分析表明，Nek2的转录在精子发生过程中以阶段特异性方式发生。在进行减数分裂的细胞中观察到最强的信号，但在单倍体细胞（I期和II期精子细胞）中也能检测到Nek2转录本。扩展这些结果，对卵巢切片进行的原位杂交显示在减数分裂活跃的卵母细胞中有强信号。此外，在围绕卵母细胞的活跃分裂的卵泡细胞和输卵管中观察到一些Nek2转录。最后，用Nek2特异性抗体对睾丸切片进行间接免疫荧光染色证实，该激酶在精母细胞中高度表达，在早期精子细胞中表达程度较低。综上所述，这些结果表明Nek2不仅在有丝分裂期间，而且在减数分裂期间可能都发挥重要作用。
