Mesoderm Posterior 1 Homolog (MESP1)

The Mesp1 transcript encodes a 243-amino acid putative transcription factor containing a basic helix-loop-helix (bHLH) motif.Both MESP1 and MESP2 contain a unique CPXCP motif immediately C-terminal to the bHLH domain. The N- and C-terminal domains of MESP1 are separated by a 2-repeat GQ region, which in MESP2 is expanded to 13 repeats.At 7.5 dpc, Mesp1 expression was detected at the base of the allantois. Shortly thereafter, expression spread to the lateral margins of the tail bud mesoderm, in a pattern corresponding to that of the initial migration of primordial germ cells, before disappearing. No Mesp1 expression was detected in later development or in adult tissues except in testis, in which a different isoform from that seen in early mesoderm was observed.