FBXO22 deficiency defines a pleiotropic syndrome of growth restriction and multi-system anomalies associated with a unique epigenetic signature

Abstract

FBXO22 encodes an F-box protein which acts as a substrate-recognition component of the SKP1-CUL1-F-box (SCF) E3 ubiquitin ligase complex. Despite its known roles in the post-translational ubiquitination and degradation of specific substrates, including histone demethylases, the impact of FBXO22 on human development remains unknown. Here, we characterize a pleiotropic syndrome with prominent prenatal onset growth restriction and notable neurodevelopmental delay across 14 cases from 12 families. Through exome and genome sequencing, we identify three distinct homozygous loss-of-function FBXO22 variants segregating with the disease: p.(Arg53Serfs*13), p.(Pro3Leufs*3) and p.(Val240Alafs*6), all predicted to lead to premature translation termination due to frameshift effects. We confirm that patient-derived primary fibroblasts are bereft of FBXO22 and show increased levels of the known substrate histone H3K9 demethylase KDM4B. Accordingly, we delineate a unique epigenetic signature for this disease in peripheral blood. Altogether, we identify and demonstrate that FBXO22 deficiency leads to a pleiotropic syndrome in humans encompassing growth restriction and neurodevelopmental delay, the pathogenesis of which may be explained by broad chromatin alterations.