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. Overall design: 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.