Shp2 knockdown and Noonan/LEOPARD mutant Shp2-induced gastrulation defects

Area of Science:

• Developmental Biology
• Cell Biology
• Genetics

Background:

• Shp2 is a cytoplasmic protein-tyrosine phosphatase vital for normal development.
• Mutations in Shp2 cause Noonan syndrome (activating) and LEOPARD syndrome (inactivating) in humans.
• The precise cellular mechanisms underlying these syndromes are not fully understood.

Purpose of the Study:

• To investigate the role of Shp2 in early zebrafish development.
• To elucidate the cell biological basis of Noonan and LEOPARD syndromes.
• To identify downstream signaling pathways regulated by Shp2.

Main Methods:

• Morpholino-mediated knockdown of Shp2 in zebrafish embryos.
• Cell tracing experiments to analyze cell movements during gastrulation.
• In situ hybridization to assess cell fate.
• Generation and expression of zebrafish Shp2 mutants mimicking human Noonan and LEOPARD mutations.
• Rescue experiments using active Fyn, Yes, and RhoA.

Main Results:

• Shp2 knockdown disrupted gastrulation, specifically convergence and extension cell movements, without affecting cell fate.
• Noonan and LEOPARD mutant Shp2s, mimicking human disease mutations, induced similar cell movement defects.
• Expression of these mutant Shp2s phenocopied craniofacial and cardiac defects observed in human patients.
• Src family kinases (Fyn, Yes) and RhoA were identified as downstream effectors of Shp2 signaling.

Conclusions:

• Shp2 is essential for normal cell movements during gastrulation, particularly convergence and extension.
• Dysfunctional Shp2 signaling, as seen in Noonan and LEOPARD syndromes, underlies critical developmental defects.
• These findings highlight early gastrulation cell movement defects as a potential diagnostic indicator for Noonan and LEOPARD syndromes.