Human Genetics of Atrial Septal Defect.

Although atrial septal defects (ASD) can be subdivided based on their anatomical location, an essential aspect of human genetics and genetic counseling is distinguishing between isolated and familiar cases without extracardiac features and syndromic cases with the co-occurrence of extracardiac abnormalities, such as developmental delay. Isolated or familial cases tend to show genetic alterations in genes related to important cardiac transcription factors and genes encoding for sarcomeric proteins. By contrast, the spectrum of genes with genetic alterations observed in syndromic cases is diverse. Currently, it points to different pathways and gene networks relevant to the dysregulation of cardiomyogenesis and ASD pathogenesis. Therefore, this chapter reflects the current knowledge and highlights stable associations observed in human genetics studies. It gives an overview of the different types of genetic alterations in these subtypes, including common associations based on genome-wide association studies (GWAS), and it highlights the most frequently observed syndromes associated with ASD pathogenesis.

NKX2-5 variants screening in patients with atrial septal defect in Indonesia.

BACKGROUND: NKX2-5 variant in atrial septal defect patients has been reported. However, it is not yet been described in the Southeast Asian population. Here, we screened the NKX2-5 variants in patients with atrial septal defect (ASD) in the Indonesian population. METHOD: We recruited 97 patients with ASD for genetic screening of the NKX2-5 variant using Sanger sequencing. RESULTS: We identified three variants of NKX2-5: NM_004387.4:c.63A>G at exon 1, NM_004387.4:c.413G>A, and NM_004387.4:c.561G>C at exon 2. The first variant is commonly found (85.6%) and benign. The last two variants are heterozygous at the same locus. These variants are rare (3.1%) and novel. Interestingly, these variants were discovered in familial atrial septal defects with a spectrum of arrhythmia and severe pulmonary hypertension. CONCLUSION: Our study is the first report of the NKX2-5 variant in ASD patients in the Southeast Asian population, including a novel heterozygous variant: NM_004387.4:c.413G>A and NM_004387.4:c.561G>C. These variants might contribute to familial ASD risk with arrhythmia and severe pulmonary hypertension. Functional studies are necessary to prove our findings.

Familial Atrial Septal Defect and Sudden Cardiac Death: Identification of a Novel NKX2-5 Mutation and a Review of the Literature.

OBJECTIVE: Atrial septal defect (ASD) is the second most common congenital heart defect (CHD) and is observed in families as an autosomal dominant trait as well as in nonfamilial CHD. Mutations in the NKX2-5 gene, located on chromosome 5, are associated with ASD, often combined with conduction disturbances, cardiomyopathies, complex CHD, and sudden cardiac death as well. Here, we show that NKX2-5 mutations primarily occur in ASD patients with conduction disturbances and heritable ASD. Furthermore, these families are at increased risk of sudden cardiac death. RESULTS: We screened 39 probands with familial CHD for mutations in NKX2-5 and discovered a novel mutation in one family (2.5%) with ASD and atrioventricular block. A review of the literature revealed 59 different NKX2-5 mutations in 202 patients. Mutations were significantly more common in familial cases compared to nonfamilial cases (P = 7.1 × 10(-9) ). The majority of patients (74%) had ASD with conduction disturbance. Nineteen patients (15%) of 120 with familial ASD and conduction disturbance died from sudden cardiac death of which nine (8%) were confirmed mutation carriers, and 10 were possible carriers. CONCLUSIONS: NKX2-5 mutations mainly occur in familial CHD, the signature phenotype is ASD with conduction disturbances and mutation carriers are at increased risk of sudden cardiac death. We suggest that familial ASD patients should be screened for NKX2-5 mutations and, if they are mutation carriers, implantation of an implantable cardioverter-defibrillator should be considered in these patients.