Abstract 1476: Different Role Of Shp2 Mutants In Cardiomyocyte Hypertrophy In Noonan/leopard Syndrome Spectrum
Background: Hypertrophic cardiomyopathy (HCM) is the distinct cardiac phenotype in Noonan syndrome (NS) and LEOPARD syndrome (LS). We have recently demonstrated a possible correlation between phenotype of cardiac hypertrophy and phosphatase activities of SHP2, a product of the PTPN11 gene in NS and LS. The aim of the current study is to investigate whether SHP2 mutants could induce different types of cardiomyocyte hypertrophy in vitro.
Methods: Patients with HCM in NS or LS(n=8) were screened for mutations in the PTPN11 gene. The six mutations(NS:4, LS:2) were isolated and those were cloned into a pAd DEST/V5 vector. Neonatal rat cardiomyocytes (CM) were isolated and infected. After CM were cultured alone or with non-CM for 72 hrs, we performed the quantitative morphometry (surface area) in each cardiomyocyte and investigate the expression of marker genes (ANP mRNA, αskeletal-actin mRNA) responsible for cardiac hypertrophy by real-time PCR.
Results: WT(wild type)-SHP2 expressed cardiomyocyte showed significant increase in surface area compared to control (LacZ-expressed, p<0.01) in co-culture system (CM+non-CM). Overexpression of Y279C, Q510E mutants(LS type) caused additional increase in surface area of cardiomyocyte than WT (p<0.01). Moreover, significant increase in the expression of αskeletal-actin mRNA was observed in Y279C and Q510E transduced cardiomyocyte. Interestingly, however, all mutants do not induce any significant increase in surface area compared to WT and LacZ in CM culture alone.
Summary: SHP2 mutants in LS induced cardiomyocyte hypertrophy in vitro, whereas SHP2 mutants in NS did not. Q510E mutants identified in LS with severe HCM induced most significant increase in surface area of cardiomyocyte. In addition, our investigation suggests that interaction between CM and non-CM is essential requirement in cardiomyocyte hypertrophy of SHP2 mutants in LS. We need further studies to elucidate a key role of SHP2 in cardiomyocyte hypertrophy and find out therapentic target molecules involved in hypertrophic signaling via SHP2.