Screening of NKX2.5 gene in Moroccan Tetralogy of Fallot (TOF) patients: worldwide mutation rate comparisons show a significant association between R25C variant and TOF phenotype

Abstract

Background Tetralogy of Fallot is the most prevalent cyanotic congenital heart disease, occurring in 1/3 600 live births. This disorder comprises ventricular septal defect, right ventricular outflow obstruction, over-riding aorta, and right ventricular hypertrophy. The present study aims to reveal the spectrum of Nk2 homeobox 5 (NKX2-5) variants identified in a Moroccan non-syndromic tetralogy of Fallot cohort and to compare mutation rate with different studies from all over the world. Thirty-one patients with non-syndromic tetralogy of Fallot were recruited in this cross-sectional study. DNAs were extracted, and coding regions of NKX2.5 were PCR-amplified and sequenced. The obtained sequences were analyzed using different bioinformatics tools. Statistical comparisons were carried out using the R software. Results R25C mutation was found in two patients, in association with the E21E variant. The latter variant was frequently observed in the population and seems to have a potential altering effect on the splicing process. The NKX2.5 mutation rate in our tetralogy of Fallot population is around 6.4%, and no significant difference was noticed in comparison with previous studies. At the same time, a comparison of R25C mutation rate between atrial septal defect and tetralogy of Fallot worldwide populations shows a particular association of R25C mutation with tetralogy of Fallot phenotype. Conclusions This study reveals a consistency between our NKX2.5 mutation rate and those of different tetralogy of Fallot populations around the world. Our findings suggest a possible combined effect of R25C mutation and E21E variant on the carriers and emphasize particularly the significant association of R25C mutation with tetralogy of Fallot, which highlights the importance of an anticipative screening for TOF phenotype among the carriers’ offspring at the perinatal period.

Genetic insights into non-syndromic Tetralogy of Fallot

“…Bioinformatic predictions indicate that the E21E variant might impair NKX2.5 transcript splicing by removing a whole exon from the transcript, resulting in translation of a shortened protein that is most likely inactive. Further in vitro functional tests are needed to validate this finding ( EL Bouchikhi et al, 2021 ).…”

“…Several studies have also reported that variants in NKX2.5 cause a wide range of CHDs, including ASD, VSD, TOF, HLH, CoA, TGA, Double Outlet Right Ventricle (DORV), IAA, and cardiac outflow tract (OFT) anomalies; reviewed in ( Chung and Rajakumar, 2016 ). Recently, new NKX2.5 variants were discovered in a Moroccan cohort with non-syndromic TOF; a missense variant R25C and a synonymous variant E21E ( EL Bouchikhi et al, 2021 ). The R25C variant is expected to impair NKX2.5 dimerisation and impede activation of downstream target genes ( Kasahara et al, 2000 ; Dentice et al, 2006 ).…”

Mutational Assessment in NKX2-5 and ACTC1 Genes in Patients with Congenital Cardiac Septal Defect (CCSD) from Ethnic Kashmiri Population

“…The human NKX2-5 gene maps to chromosome 5q34 and consists of two exons that encode a 324-amino acid protein [ 16 ]. Previous studies evaluated the exonic regions of the NKX2-5 gene; however, recent findings instead investigate the mutations and associated CHDs in the intronic and promoter regions of the NKX2-5 gene [ 17 ]. Functional analysis has elucidated the mechanism of action in various mutations of the NKX2-5 gene and future studies are required in order to understand the involvement of NKX2-5 in complex cardiac abnormalities [ 18 ].…”