Abnormal mesoderm patterning in mouse embryos mutant for the SH2 tyrosine phosphatase Shp-2.

Shp-1, Shp-2 and corkscrew comprise a small family of cytoplasmic tyrosine phosphatases that possess two tandem SH2 domains. To investigate the biological functions of Shp-2, a targeted mutation has been introduced into the murine Shp-2 gene, which results in an internal deletion of residues 46-110 in the N-terminal SH2 domain. Shp-2 is required for embryonic development, as mice homozygous for the mutant allele die in utero at mid-gestation. The Shp-2 mutant embryos fail to gastrulate properly as evidenced by defects in the node, notochord and posterior elongation. Biochemical analysis of mutant cells indicates that Shp-2 can function as either a positive or negative regulator of MAP kinase activation, depending on the specific receptor pathway stimulated. In particular, Shp-2 is required for full and sustained activation of the MAP kinase pathway following stimulation with fibroblast growth factor (FGF), raising the possibility that the phenotype of Shp-2 mutant embryos results from a defect in FGF-receptor signalling. Thus, Shp-2 modulates tyrosine kinase signalling in vivo and is crucial for gastrulation during mammalian development.