Idh2-α-KG axis dysregulation disrupts epigenetic landscape and imprinted genes, inducing placental hypertrophy in somatic cell nuclear transfer Bos taurus

Placental hypertrophy is a major cause of pregnancy failure in somatic cell nuclear transfer (SCNT) animals, with metabolic-epigenetic crosstalk proposed as a key regulatory node, yet its molecular mechanism remains elusive. Isocitrate dehydrogenase 2 (Idh2) is a critical mitochondrial metabolic enzyme that controls the production of α-Ketoglutarate (α-KG), a central regulator of epigenetic modifications. Abnormally elevated α-KG levels were found in SCNT Bos taurus placentomes and derived placental mesenchymal cells. Further functional experiments in these cells suggested that elevated α-KG levels were associated with significant increases in 5-hydroxymethylcytosine (5hmC) and the active histone marker H3K4me3, as well as decreases in the repressive markers H3K9me3 and H3K27me3, accompanied by altered expression of ten-eleven translocation (TET) dioxygenases and lysine demethylase (KDMs). This ultimately led to the dysregulation of key imprinted genes associated with placental development, including upregulation of Insulin-like growth factor 2 receptor (Igf2r) and Zinc figer protein 597 (Znf597), and downregulation of Pleckstrin homology-like domain family A member 2 (Phlda2), Paternally expressed gene 10 (Peg10), and MAGE family member L2 (Magel2). Further analysis revealed that Idh2, a key enzyme for α-KG synthesis, was significantly upregulated in SCNT B. taurus placentas, with its promoter region exhibiting hypomethylation, increased H3K4me3 modification, and enhanced chromatin accessibility. Targeted knockdown of Idh2 via CRISPR-Cas9 or inhibition of α-KG production using specific inhibitors effectively reversed these epigenetic abnormalities and improved the placental hypertrophy phenotype. In Mus musculus validation experiments, maternal α-KG supplementation during pregnancy induced placental hypertrophy, whereas inhibiting Idh2 activity completely rescued this phenotype. This study is the first to elucidate the molecular mechanism by which Idh2-α-KG axis regulates placental development through a "metabolism-epigenetics" axis, providing novel strategies to improve cloning efficiency and potential intervention targets for treating placenta-related diseases (e.g., placental macrosomia).