Mowat-Wilson syndrome (MWS) is a severe intellectual disability (ID)-distinctive 
facial gestalt-multiple congenital anomaly syndrome, commonly associating 
microcephaly, epilepsy, corpus callosum agenesis, conotruncal heart defects, 
urogenital malformations and Hirschsprung disease (HSCR). MWS is caused by de 
novo heterozygous mutations in the ZEB2 gene. The majority of mutations lead to 
haplo-insufficiency through premature stop codons or large gene deletions. Only 
three missense mutations have been reported so far; none of which resides in a 
known functional domain of ZEB2. In this study, we report and analyze the 
functional consequences of three novel missense mutations, p.Tyr1055Cys, 
p.Ser1071Pro and p.His1045Arg, identified in the highly conserved C-zinc-finger 
(C-ZF) domain of ZEB2. Patients' phenotype included the facial gestalt of MWS 
and moderate ID, but no microcephaly, heart defects or HSCR. In vitro studies 
showed that all the three mutations prevented binding and repression of the 
E-cadherin promoter, a characterized ZEB2 target gene. Taking advantage of the 
zebrafish morphant technology, we performed rescue experiments using wild-type 
(WT) and mutant human ZEB2 mRNAs. Variable, mutation-dependent, embryo rescue, 
correlating with the severity of patients' phenotype, was observed. Our data 
provide evidence that these missense mutations cause a partial loss of function 
of ZEB2, suggesting that its role is not restricted to repression of E-cadherin. 
Functional domains other than C-ZF may play a role in early embryonic 
development. Finally, these findings broaden the clinical spectrum of ZEB2 
mutations, indicating that MWS ought to be considered in patients with lesser 
degrees of ID and a suggestive facial gestalt, even in the absence of congenital 
malformation.