Absence of GATA4 Mutations in Moroccan Patients with Atrial Septal Defect (ASD) Provides Further Evidence of Limited Involvement of GATA4 in Major Congenital Heart Defects.

OBJECTIVE: Atrial septal defect (ASD) is one of the most common types of congenital heart disease (CHD). It is mainly caused by mutations of NK2 homeobox 5, GATA binding protein 4 (GATA4), and myosin heavy chain 6 in non-syndromic cases. This study aims to carry out, for the first time, the GATA4 mutation screening in a Moroccan population affected by ASD and compare the obtained mutation rate across populations. MATERIALS AND METHODS: A total of 33 patients were enrolled in this study. DNAs were extracted from peripheral blood samples, and we performed PCR-sequencing for GATA4 coding regions. Sequences were analyzed by sequence alignment and functional impact prediction tools. Mutation rate comparisons were performed by R software using the appropriate statistical tests. RESULTS: We detected 7 variants, but no pathogenic mutation was revealed, except for Asn352= that was assessed by human splicing finder algorithms to have a potential impairing effect on the splicing mechanism. Until proven by in vitro functional studies, the current pathogenic mutation rate in our cohort seems to be 0%. Statistical comparison with previous studies from all over the world shows no significant difference. Seemingly, comparison of previous GATA4 mutation rates among tetralogy of Fallot (TOF) populations shows no significant difference. CONCLUSION: The low rates of GATA4 mutations observed throughout ASD and TOF international populations may suggest a limited causality of GATA4 mutations in the main CHDs, which further confirms the co-involvement of additional genetic and/or environmental factors in the manifestation of these phenotypes.

GATA4 molecular screening and assessment of environmental risk factors in a Moroccan cohort with tetralogy of Fallot.

BACKGROUND: Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect (CHD) with an incidence of 1/3600 live births. This disorder was associated with mutations in the transcription factors involved in cardiogenesis, like Nk2 homeobox5 (NKX2-5), GATA binding protein4 (GATA4) and T-BOX1 (TBX1). GATA4 contributes particularly to heart looping and differentiation of the second heart field. OBJECTIVES: The aim of this study was to screen a Moroccan cohort with tetralogy of Fallot for GATA4 mutations, and to assess environmental risk factors that could be involved in the occurrence of this disorder. METHODS: Thirty-one non-syndromic TOF patients, enrolled between 5th April 2014 and 18th June 2015, were screened for GATA4 mutations using direct sequencing of GATA4 coding exons. Statistical assessment of different risk factors, which is a retrospective study, was carried out using Chi-square and Fisher's exact tests. RESULTS: We identified seven exonic variants in nine patients (two missense and five synonymous variants); in addition of eight intronic variants. Assessment of environmental risk factors shows significant association of maternal passive smoking with TOF in the Moroccan population. CONCLUSION: The present study allowed, for the first time, the molecular and environmental characterisation of Moroccan TOF population. Our findings emphasise particularly the strong association of passive smoking with the emergence of tetralogy of Fallot.

Novel NKX2-5 germline mutation in a Moroccan child with transitional atrio-ventricular septal defect (tAVSD).

Atrioventricular septal defect is a complex congenital heart defects (CHD) with a prevalence of approximately 4% of all CHDs. Transitional form of atrio-ventricular septal defect (tAVSD) associates ostium primum atrial septal defect, common atrioventricular annulus with distinct atrioventricular valvar orifices in addition of restrictive ventricular septal defect. We describe in this report clinical and molecular features of a Moroccan boy that carries a novel NK2 homeobox 5 (NKX2-5) germline mutation (Pro141Ala), and exhibits a transitional atrio-ventricular septal defect. This phenotype has never been reported in association with NKX2-5 germline mutations. Pro141Ala is a non-reported pathogenic mutation that alters the nuclear localization signal sequence, leading to disruption of NKX2-5 nuclear translocation mechanism. Such alteration would decrease nuclear transcriptional activity of NKX2-5 and impair cardiogenesis process. The present report comes to widen the phenotypic spectrum of congenital heart disease caused by NKX2-5 germline mutations, and highlights as well the importance of the nuclear localization system in NKX2-5 activity.

Noonan syndrome-causing genes: Molecular update and an assessment of the mutation rate.

Noonan syndrome is a common autosomal dominant disorder characterized by short stature, congenital heart disease and facial dysmorphia with an incidence of 1/1000 to 2500 live births. Up to now, several genes have been proven to be involved in the disturbance of the transduction signal through the RAS-MAP Kinase pathway and the manifestation of Noonan syndrome. The first gene described was PTPN11, followed by SOS1, RAF1, KRAS, BRAF, NRAS, MAP2K1, and RIT1, and recently SOS2, LZTR1, and A2ML1, among others. Progressively, the physiopathology and molecular etiology of most signs of Noonan syndrome have been demonstrated, and inheritance patterns as well as genetic counseling have been established. In this review, we summarize the data concerning clinical features frequently observed in Noonan syndrome, and then, we describe the molecular etiology as well as the physiopathology of most Noonan syndrome-causing genes. In the second part of this review, we assess the mutational rate of Noonan syndrome-causing genes reported up to now in most screening studies. This review should give clinicians as well as geneticists a full view of the molecular aspects of Noonan syndrome and the authentic prevalence of the mutational events of its causing-genes. It will also facilitate laying the groundwork for future molecular diagnosis research, and the development of novel treatment strategies.