Alternative splicing of the Izumo1 gene ensures triggering gamete fusion in mice.
Alternative splicing of the Izumo1 gene ensures triggering gamete fusion in mice.
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Izumo1 基因的选择性剪接确保触发小鼠配子融合。
DOI：
10.1038/s41598-019-40130-7
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发表时间：
2019
影响因子：
4.6
通讯作者：
and Naokazu Inoue
中科院分区：
文献类型：
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作者：
Takako Saito;Ikuo Wada;and Naokazu Inoue
IZUMO1是一种精子顶体膜蛋白，通过识别卵母细胞表面的JUNO并伴随IZUMO1-JUNO复合物的形成，对哺乳动物受精至关重要。在这里，我们报道了一个新的izumo1基因剪接变异（IZUMO1_v2），它具有一个独特的52个氨基酸长的信号序列，转录自外显子1b。虽然睾丸中izumo1_v2的mRNA量比原IZUMO1_v1低76倍，但细胞-卵母细胞实验表明，表达izumo1_v2的COS-7细胞具有附着于IZUMO1_v1的卵母细胞的能力。为了阐明IZUMO1_v2的生理功能，我们通过CRISPR/Cas9系统构建了IZUMO1_v1特异性敲除小鼠系，该系在IZUMO1_v1初始蛋氨酸密码子附近有9个碱基缺失。IZUMO1_v1基因敲除的雄鼠精子中IZUMO1蛋白水平降低0.19倍；然而，与野生型小鼠相比，生育能力的降低仅受到最小的影响，这表明只有一小部分IZUMO1足以触发精子-卵子融合。我们提出，当剪接受到干扰时，产生IZUMO1_v2的备选剪接可能在小鼠中起到故障安全的作用。
IZUMO1 is a sperm acrosomal membrane protein that is essential for mammalian fertilization through recognition of JUNO on the oocyte surface and accompanying IZUMO1-JUNO complex formation. Here, we report a newIzumo1gene splicing variant (IZUMO1_v2) with a unique 52-amino-acid-long signal sequence transcribed from Exon 1b. Although the mRNA amount ofIzumo1_v2is 76 times lower than that of the originalIzumo1(IZUMO1_v1) in the testis, the cell-oocyte assay indicates that IZUMO1_v2-expressing COS-7 cells have the ability to attach to the oocyte equivalent of IZUMO1_v1. To clarify the physiological function of IZUMO1_v2, we produced an IZUMO1_v1-specific knockout mouse line with a nine-base deletion adjacent to the initial methionine codon of IZUMO1_v1 by the CRISPR/Cas9 system. The IZUMO1_v1 knockout male mice carry 0.19-fold lower level of IZUMO1 protein in the spermatozoon; however, reduction in fertility was only minimally affected compared to the wild-type mice, suggesting that only a small fraction of IZUMO1 is sufficient for triggering sperm-egg fusion. We propose that the alternative splicing generating IZUMO1_v2 might function as a fail-safe in mouse for when splicing is disturbed.