A gain-of-function mutation in CITED2 is associated with congenital heart disease.

CITED2 is a transcription co-activator that interacts with TFAP2 and CBP/ P300 transcription factors to regulate the proliferation and differentiation of the cardiac progenitor cells. It acts upstream to NODAL-PITX2 pathways and regulates the left-right asymmetry. Both human genetic and model organism studies have shown that altered expression of CITED2 causes various forms of congenital heart disease. Therefore, we sought to screen the coding region of CITED2 to identify rare genetic variants and assess their impact on the structure and function of the protein. Here, we have screened 271 non-syndromic, sporadic CHD cases by Sanger's sequencing method and detected a non-synonymous variant (c.301C>T, p.P101S) and two synonymous variants (c.21C>A, p.A7A; c.627C>G, p.P209P). The non-synonymous variant c.301C>T (rs201639244) is a rare variant with a minor allele frequency of 0.00011 in the gnomAD browser and 0.0018 in the present study. in vitro analysis has demonstrated that p.P101S mutation upregulates the expression of downstream target genes Gata4, Mef2c, Nfatc1&2, Nodal, Pitx2, and Tbx5 in P19 cells. Luciferase reporter assay also demonstrates enhanced activation of downstream target promoters. Further, in silico analyses implicate that increased activity of mutant CITED2 is possibly due to phosphorylation of Serine residue by proline-directed kinases. Homology modeling and alignment analysis have also depicted differences in hydrogen bonding and tertiary structures of wild-type versus mutant protein. The impact of synonymous variations on the mRNA structure of CITED2has been analyzed by Mfold and relative codon bias calculations. Mfold results have revealed that both the synonymous variants can alter the mRNA structure and stability. Relative codon usage analysis has suggested that the rate of translation is attenuated due to these variations. Altogether, our results from genetic screening as well as in vitro and in silico studies support a possible role of nonsynonymous and synonymous mutations in CITED2contributing to pathogenesis of CHD.