Essential Role of Mg2+ for Mouse Preimplantation Embryo Development Revealed by TRPM7 Chanzyme Deficient Gametes

TRPM7 (transient receptor potential cation channel subfamily M member 7) is a chanzyme with channel and kinase domains essential for embryo development. Using gamete-specific Trpm7-null lines, we report that TRPM7-mediated Mg2+ influx is indispensable for reaching the blastocyst stage. TRPM7 was expressed dynamically from gametes to blastocysts, displaying stage-specific and distinct localizations on the plasma membrane, cytoplasm, and nucleus, and undergoes cleavage that produces C- terminal kinase fragments. TRPM7 underpinned Mg2+ homeostasis throughout this time, and excess Mg2+ but not Zn2+ or Ca2+ overcame the arrest of Trpm7-null embryos; expressing Trpm7 mRNA restored development, but mutant versions failed or were less effective. Transcriptomic analyses of embryos lacking Trpm7 revealed an abundance of oxidative stress-pathway genes, confirmed by mitochondrial dysfunction, and a reduction of transcription factor networks essential for proliferation; Mg2+ supplementation corrected these defects. Hence, TRPM7 underpins Mg2+ homeostasis in preimplantation embryos, prevents oxidative stress, and promotes gene expression patterns necessary for developmental progression and cell lineage specification. RNAseq was performed in control or Trpm7 knockout metaphase II eggs, 1-cell, 2-cell, 4-cell, and 8-cell embryos, morulas, and blastocysts, as well as embryos cultured for 24 or 48 hours from the 2-cell stage in the presence of 10 mM MgSO4.TRPM7（瞬时受体电位阳离子通道亚家族M成员7，transient receptor potential cation channel subfamily M member 7）是一种兼具通道与激酶结构域的通道酶（chanzyme），其结构域对于胚胎发育至关重要。本研究借助配子特异性Trpm7敲除品系，证实TRPM7介导的Mg²+内流是胚胎发育至囊胚期的必要条件。TRPM7在配子至囊胚的整个发育进程中呈动态表达特征，具有阶段特异性，且在细胞膜、细胞质与细胞核中呈现出独特的亚细胞定位；该蛋白还会发生裂解，产生C端激酶片段。TRPM7在该发育全程维持Mg²+稳态，仅过量Mg²+（而非Zn²+或Ca²+）可挽救Trpm7敲除胚胎的发育阻滞；外源性导入Trpm7 mRNA可恢复胚胎发育，但突变型mRNA则无法发挥作用或效果有限。对Trpm7缺失胚胎的转录组分析显示，氧化应激通路基因显著富集，该结果通过线粒体功能障碍实验得到验证，同时调控细胞增殖的转录因子网络表达水平下调；补充Mg²+可有效纠正上述异常表型。综上，TRPM7通过维持植入前胚胎的Mg²+稳态，抑制氧化应激发生，并促进发育进程与细胞谱系特化所必需的基因表达程序。本研究对对照组或Trpm7敲除的MII期卵母细胞、1细胞期、2细胞期、4细胞期、8细胞期胚胎，桑椹胚及囊胚，以及在2细胞期体外培养24小时或48小时且添加10 mM硫酸镁的胚胎开展了RNA测序（RNAseq）。