Transcription factor with important role in somitogenesis. Defines the rostrocaudal patterning of the somite by participating in distinct Notch pathways. Regulates also the FGF signaling pathway. Specifies the rostral half of the somites. Generates rostro-caudal polarity of somites by down-regulating in the presumptive rostral domain DLL1, a Notch ligand. Participates in the segment border formation by activating in the anterior presomitic mesoderm LFNG, a negative regulator of DLL1-Notch signaling. Acts as a strong suppressor of Notch activity. Together with MESP1 is involved in the epithelialization of somitic mesoderm and in the development of cardiac mesoderm. May play a role with Tcf15 in the differentiation of myotomal and sclerotomal cells by regulating Pax family genes. Controls also the expression of the protocadherin PCDH8/PAPC, EPHA4, RIPPLY2, NOTCH2, FGFR1, and CER1. Binds to the E-boxes within the EPH4A and RIPPLY2 enhancers. First transiently detected in the nascent mesoderm at the onset of gastrulation. A second site of expression is detected at 8 dpc in the rostral region of the presomitic mesoderm inmediately before segmentation. Down-regulated immediately after the formation of the segmented somites before 13.5 dpc. Initially expressed throughout the length of one somite, and then quickly repressed in the presumptive caudal region. Mesp2 is involved in the rapid down-regulation of its own expression in the presumptive caudal half of the somite. Down-regulated in NOTCH1, DLL1, RBPJ and FOXC1/FOXC2 mutant mice. Expression in the anterior presomitic mesoderm is periodic, dissipating once the segmental border is established. Negatively regulated by RIPPLY2. Positively regulated by TBX6 and Notch signaling. Degraded by the proteasome. Phosphorylated. Mice die shortly after birth and show caudal truncation and severe skeletal malformations. Lack of segmentation and impaired segment polarity of the paraxial mesoderm are the primary defects. Mutants show altered expression of MEOX1, Pax1, and DLL1 and lack of expression of Notch1, Notch2, and FGFR1. Mice lacking Mesp1 and Mesp2 die around 9.5 dpc. The major defect is the apparent lack of any mesodermal layer between endoderm and ectoderm and a defect in the migratory activity of mesodermal cells.