日本科学家25日报告说,他们在面包酵母体内发现了8种与染色体数目异常相关的基因。由于人体内也存在类似基因,这项成果可能有助于研究染色体数目异常引起的流产和唐氏综合征等疾病。
人类染色体共有23对,46条。46条染色体经过减数分裂平均分配到形成的精子或卵子中,受精后,染色体数目便恢复到46条。约95%的唐氏综合征患者由“21三体”导致,即在卵细胞减数分裂过程中,一条21号染色体不分离,使受精卵的21号染色体增至3条,而不是正常情况下的两条。而流产很多情况下也是因为染色体数目出现异常。
减数分裂中会发生同源染色体配对和基因重组,以往的研究发现,如果不经过基因重组,染色体就不能正常分离,最终造成精子和卵子染色体数目异常。
日本大阪大学蛋白质研究所教授篠原彰等研究人员在25日的《自然·遗传学》杂志网络版上发表文章说,他们以染色体数目异常而不能正常产生孢子(相当于精子或卵子)的面包酵母为对象,研究它们体内的基因情况。
研究人员发现,这些面包酵母体内有8个与染色体异常相关的基因,其中任何一个基因出现问题,酵母染色体基因不能重组的概率都会提高。他们还发现,这8个基因合成的蛋白质会结合成一个复合体,不能形成复合体的酵母染色体数目也会发生偏差。
研究人员推测,这种蛋白质复合体保证染色体基因重组顺利进行,如果能证实人类的流产等是由这一复合体功能下降引起的,将有助于诊断和治疗相关疾病。
生物谷推荐原文提要:
Crossover assurance and crossover interference are distinctly regulated by the ZMM proteins during yeast meiosis
Miki Shinohara, Steve D Oh, Neil Hunter & Akira Shinohara,
Abstract:Meiotic crossing-over is highly regulated such that each homolog pair typically receives at least one crossover (assurance) and adjacent crossovers are widely spaced (interference). Here we provide evidence that interference and assurance are mechanistically distinct processes that are separated by mutations in a new ZMM (Zip, Msh, Mer) protein from Saccharomyces cerevisiae, Spo16. Like other zmm mutants, spo16 cells have defects in both crossing-over and synaptonemal complex formation. Unlike in previously characterized zmm mutants, the residual crossovers in spo16 cells show interference comparable to that in the wild type. Spo16 interacts with a second ZMM protein, Spo22 (also known as Zip4), and spo22 mutants also show normal interference. Notably, assembly of the MutS homologs Msh4 and Msh5 on chromosomes occurs in both spo16 and spo22, but not in other zmm mutants. We suggest that crossover interference requires the normal assembly of recombination complexes containing Msh4 and Msh5 but does not require Spo16- and Spo22-dependent extension of synaptonemal complexes. In contrast, crossover assurance requires all ZMM proteins and full-length synaptonemal complexes.