This thesis describes the use of zebrafish to study Noonan-(NS) and LEOPARD syndromes (LS), two autosomal dominant disorders with overlapping symptoms, caused by mutations in protein-tyrosine... Show moreThis thesis describes the use of zebrafish to study Noonan-(NS) and LEOPARD syndromes (LS), two autosomal dominant disorders with overlapping symptoms, caused by mutations in protein-tyrosine phosphatase, non-receptor type 11 (PTPN11). Intriguingly, while NS mutations result in a more __active__ state of Shp2, LS mutations give rise to a PTP defective protein. First, we studied the role of ptpn11 in zebrafish embryonic development. Whereas ptpn11a is crucial for development ptpn11b seems dispensible. Moreover, using phoshoproteomics we show hypo- and hypertyrosyl phosphorylation of Fer kinase and PZR (Protein zero related), respectively and study their roles as (potential) interacting proteins in the etiology of both NS and LS. Defective heart development is a prominent symptom of NS and LS. Embryos expressing NS and LS Shp2 showed impaired expression of laterality markers, impaired cilia function in Kupffer__s vesicle and at later stages, heart function defects. Finally we identified several mutations in Alpha-2-Macroglobulin-Like-1 (A2ML1) in patients diagnosed with NS. Functional characterization of these mutations in zebrafish showed NS-like developmental defects. This is the first example of an extracellular factor in a disorder clinically related to NS and LS, providing potential new leads for better understanding of the molecular basis of these developmental syndromes. Show less
