MSGN1 (mesogenin 1) is a basic-helix-loop-helix transcription factor that plays a crucial role in early vertebrate development, specifically in the formation and specification of paraxial mesoderm 1. MSGN1 functions as a presomitic mesoderm marker gene that is induced by Wnt signaling during early embryonic development 2. The gene is progressively expressed during the differentiation pathway from mesoderm to somite formation, following normal patterns of embryonic myogenesis 3. Mechanistically, MSGN1 expression levels are regulated by FGF signaling concentration, with higher FGF levels supporting posterior presomitic mesoderm formation where MSGN1 expression depends on FGF ligand concentration 4. MSGN1 also responds to retinoic acid receptor inverse agonist treatment, which promotes paraxial mesoderm lineage differentiation 5. Disease relevance includes a novel skeletal dysplasia syndrome associated with a gain-of-function mutation (p.Arg125Leu) that causes severe skeletal abnormalities including mesomelic dysplasia and vertebral defects 1. The mutant protein shows enhanced transcriptional activity compared to wild-type, leading to altered downstream signaling including ectopic tbx6 and bmp2 expression 1. MSGN1 variants have also been associated with Chiari malformation type I susceptibility 6.