Mutation Analysis of TBX1 in Children with Conotruncal Heart Anomalies

Abstract

To the Editor: Conotruncal heart anomalies (CTA) are structural malformations involving the outflow tract. While the exact incidence of CTA in India is not known, it remains the most common type of structural birth defect with a major impact on pediatric morbidity and mortality. While most CTA are sporadic, a few are associated with genetic syndromes; the 22q11 deletion syndrome (22q11.2DS) being the predominate one. The CTA related to the 22q11.2DS are usually associated with a common 3 Mb or 1.5 Mb proximally deleted region, both of which include the TBX1 gene. However, mutations of the TBX1 gene have also been reported in patients who do not have the 22q11.2 deletion but present with CTA. The TBX1 gene encodes a transcription factor of the T-box family and mouse models have demonstrated that TBX1 haploinsufficiency cause cardiac outflow tract lesions.In a case-control study involving 96 cases of CTA and 100 control subjects, ranging in age from newborns to 18 y, fluorescence in situ hybridization (FISH) was performed on the cases to rule out the 22q11.2 μ-deletion. Further, screening for mutations or sequence variants in four exons of the T-box region, which showed 98 % homology to mouse TBX1, was performed using Sanger sequencing.One out of the 96 cases with CTA (1 %) was found to have the 22q11.2 μ-deletion. However, no pathogenic mutations or sequence variants of TBX1 were detected in the patients and healthy controls. While this is in agreement with the report by Conti et al. [1], it is also in contrast with a few studies that have documented either mutations or polymorphisms in TBX1 associated with isolated CTA [2-5]. Our results, though negative, provide corroborative evidence that TBX1 mutations may not be associated with CTA in the selected pediatric population.

Use of Array Comparative Genomic Hybridization for the Diagnosis of DiGeorge Syndrome in Saudi Arabian Population

“…Ten minutes before harvesting, 65 μL colcemid was added to the culture flask to induce metaphase stage arrest [Driscoll et al, 1993] after which cells were pelleted by centrifugation at 900 rpm for 6 min and resuspended in 0.5 mL of PBS. Treatment with prewarmed potassium chloride hypotonic solution (10 mL; 0.075 M KCl) was carried out at 37 ° C for 20 min [Koshy et al, 2016]. Freshly prepared Carnoy's fixative (10 mL of methanol:glacial acetic acid, 3: 1) was slowly added, mixed, and cells were centrifuged.…”