Preprint implicates IRX4 variants in non-syndromic and Down syndrome-associated congenital heart disease

A bioRxiv preprint describes sequencing of the IRX4 gene — which encodes a TALE-homeodomain transcription factor essential for cardiac ventricular development — in a cohort of 205 individuals with non-syndromic congenital heart disease (CHD), alongside 24 individuals with Down syndrome (DS) and CHD, 27 individuals with DS without CHD, and 150 healthy controls.

Two novel missense variants (p.Ser24Asn and p.Thr217Iso) were identified exclusively in non-syndromic CHD cases, and a previously reported variant (rs2232376) was found across both non-syndromic and DS-with-CHD groups but not in DS cases without cardiac involvement. The authors propose that IRX4 variants may act as a contributory factor in CHD susceptibility, including within the context of trisomy 21, where cardiac malformations affect approximately 40–50% of individuals.

In murine models, loss of Irx4 is associated with impaired ventricular function and cardiomyopathy, providing prior mechanistic plausibility. The preprint has not been peer-reviewed, and the cohort sizes — particularly for DS subgroups — are modest, which limits statistical confidence. Replication in larger, independent cohorts and functional characterisation of the identified variants are required before firm conclusions can be drawn. The findings will be of interest to researchers in cardiovascular genetics and those working on the genetic modifiers of DS-associated phenotypes.