NSD1 heterozygosity disrupts fetal growth and neonatal survival and placental abnormalities in mice

This study investigates the developmental consequences of Nsd1 haploinsufficiency in mice. NSD1 is a histone methyltransferase that catalyzes H3K36me2 and plays a key role in transcriptional regulation during development. Although homozygous deletion of Nsd1 results in embryonic lethality, the phenotypic impact of heterozygosity has remained unclear. We demonstrate that Nsd1+/- embryos are present at Mendelian ratios during gestation but exhibit significantly reduced survival within 48 hours after birth. Nsd1+/- fetuses display reduced body weight, increased placental weight, and decreased global H3K36me2 levels in the brain and placenta. Histological analysis reveals expansion of the placental junctional zone, and transcriptomic profiling indicates broad gene expression changes without enrichment of specific gene ontologies. These findings suggest that Nsd1 heterozygosity leads to subtle epigenetic and structural abnormalities during late gestation that impair neonatal adaptation and viability