Variants in ZFX Cause an X-linked Neurodevelopmental Disorder with Recurrent Facial Gestalt

Pathogenic variants in multiple X-linked genes have been implicated in syndromic and non- syndromic intellectual disability disorders. The gene ZFX on Xp22.11 encodes a transcription factor that has been linked to diverse processes including oncogenesis and development, but germline variants have not previously been reported in association with disease. Here, we present clinical and molecular characterization of 18 patients with germline ZFX variants. Exome or genome sequencing revealed 11 variants in 18 subjects (14 males and 4 females) from 16 unrelated families. Four missense variants were identified in 11 subjects, with seven frameshift variants in the remaining individuals. Clinical findings included developmental delay/intellectual disability, behavioral abnormalities, hypotonia, and congenital anomalies. Overlapping and recurrent facial features were identified in all subjects, including thickening and medial broadening of eyebrows, variations in the shape of the face, external eye abnormalities, smooth and/or long philtrum and ear abnormalities. Hyperparathyroidism was found in 4 families with missense variants and enrichment of different types of tumors was also observed. In molecular studies, variants in the DNA-binding domain demonstrated differential expression of target genes relative to wild-type ZFX in cultured cells, suggesting a gain or loss of transcriptional activity. Additionally, a zebrafish model of ZFX loss displayed an altered behavioral phenotype, supporting the pathogenicity of predicted loss- of-function frameshift variants. Our clinical and experimental data support that variants in ZFX cause a novel X-linked intellectual disability syndrome characterized by a recurrent facial gestalt, neurocognitive and behavioral abnormalities, and an increased risk for congenital anomalies and hyperparathyroidism. RNA-seq and ChIP-seq in HEK293T Kidney Cells and ZFX/ZNF711 Knockout HEK293T Kidney Cells