A gain-of-function TBX20 mutation causes congenital atrial septal defects, patent foramen ovale and cardiac valve defects

Abstract

BackgroundOstium secundum atrial septal defects (ASDII) account for approximately 10% of all congenital heart defects (CHD), and mutations in cardiac transcription factors, including TBX20, were identified as an underlying cause for ASDII. However, very little is known about disease penetrance in families and functional consequences of inherited TBX20 mutations.MethodsThe coding region of TBX20 was directly sequenced in 170 ASDII patients. Functional consequences of one novel mutation were investigated by surface plasmon resonance, CD spectropolarymetry, fluorescence spectrophotometry, luciferase assay and chromatin immunoprecipitation.ResultsWe found a novel mutation in a highly conserved residue in the T-box DNA binding domain (I121M) segregating with CHD in a three generation kindred. Four mutation carriers revealed cardiac phenotypes in terms of cribriform ASDII, large patent foramen ovale or cardiac valve defects. Interestingly, tertiary hydrophobic interactions within the mutant TBX20 T-box were significantly altered leading to a more dynamic structure of the protein. Moreover, Tbx20-I121M resulted in a significantly enhanced transcriptional activity, which was further increased in the presence of co-transcription factors GATA4/5 and NKX2-5. Occupancy of DNA binding sites on target genes was also increased.ConclusionsWe suggest that TBX20-I121M adopts a more fluid tertiary structure leading to enhanced interactions with cofactors and more stable transcriptional complexes on target DNA sequences. Our data, combined with that of others, suggest that human ASDII may be related to loss-of-function as well as gain-of-function TBX20 mutations.

A novel variant in TBX20 (p.D176N) identified by whole-exome sequencing in combination with a congenital heart disease related gene filter is associated with familial atrial septal defect

“…Previous studies have demonstrated that identified ASD-related TBX20 mutations are all in the T-box DNA binding domain (109-288 AA) except p.A63T ( Fig. 3; Table 3) (Kirk et al, 2007;Liu et al, 2008;Qian et al, 2009;Posch et al, 2010a). Therefore, although in vitro assays were not performed in our study, we still believed that the mutation (p.D176N) in this study plays a critical role in CHDs.…”

“…TBX20 associated directly with other cardiac transcription factors, namely, the homeodomain factor NKX2-5 and zinc finger factor GATA4 and GATA5 (Stennard et al, 2003). Modification of amino acid from aspartic acid to asparagine may not prevent binding to its target DNA site, but there are other possibilities, such as an influenced rate of scanning of DNA or co-factors for interaction, or abnormal structure stability when bound to co-factors (Posch et al, 2010a). Previous studies have demonstrated that identified ASD-related TBX20 mutations are all in the T-box DNA binding domain (109-288 AA) except p.A63T ( Fig.…”

“…Qian et al (2009) reported that two different variants of TBX20 were found in four children with ASD with or without other CHD. Posch et al (2010a) identified a TBX20 missense variant in a patient with ASD with additional TOF and cardiac valve defect (Table 3).…”

“…In the developing mouse embryos, tbx20 is expressed in cardiac progenitor cells, as well as in the developing myocardium and endothelial cells associated with endocardial cushions, the precursor structures for the cardiac valves and the atrioventricular septum, which implies that tbx20 is essential for proper heart development. Loss function of tbx20 in the mouse has been found in connection with various forms of congenital heart defects, including defects in septation, valvulogenesis, cardiomyopathy, and arrhythmia (Stennard et al, 2003;Stennard et al, 2005;Kirk et al, 2007;Liu et al, 2008;Posch et al, 2010a;Sotoodehnia et al, 2010;Shen et al, 2011;Zhang et al, 2011;Qiao et al, 2012).…”

CCN1 Mutation is Associated with Atrial Septal Defect

“…Various mutations in transcription factors and sarcomeric genes were described in different studies [3]. We have analyzed different genes involved in the pathogenesis of CHDs and could identify mutations in ASD patients [4,5,6].…”