Deleterious, protein-altering variants in the transcriptional coregulator ZMYM3 in 27 individuals with a neurodevelopmental delay phenotype [RNA-seq]
Neurodevelopmental disorders (NDDs) result from highly penetrant variation in hundreds of different genes, some of which have not yet been identified. Using the MatchMaker Exchange, we assembled a cohort of 27 individuals with rare, protein-altering variation in the transcriptional coregulator gene ZMYM3, located on the X chromosome. Most (n=24) individuals were males, 17 of which have a maternally inherited variant and four of which have de novo variants. Overlapping features included developmental delay, intellectual disability, behavioral abnormalities, and a specific facial gestalt in a subset of males. Variants in almost all individuals (n=26) are missense, including six with variants that have arisen independently at the same codon at least two times. Four unrelated probands were identified with inherited variation at Arg441 (Arg441Trp or Arg441Gln), a site at which variation has been previously seen in NDD-affected siblings, and two individuals have de novo variation at Arg1294 (Arg1294Cys). All variants affect evolutionarily conserved sites, and most are predicted to damage protein structure or function. ZMYM3 is relatively intolerant to variation in the general population, is widely expressed across human tissues, and encodes a component of the KDM1A-RCOR1 chromatin-modifying complex. ChIP-seq experiments on one mutant, Arg1274Trp, indicate dramatically reduced genomic occupancy, supporting a hypomorphic effect. Similarly, RNA-seq comparing mutant cells to reference revealed numerous expression changes. Such changes were not seen in edited cells harboring a likely benign variant, Arg688His. While we are unable to perform statistical evaluations to support a conclusive causative role for variation in ZMYM3 in disease, the totality of the evidence, including 27 affected individuals, recurrent variation affecting at least two codons, overlapping phenotypic features, protein-modeling data, evolutionary constraint, and experimentally-confirmed functional effects strongly support ZMYM3 as a novel NDD gene. Overall design: HepG2 cells were edited by CRISPR/Cas9 to add a FLAG epitope tag to ZMYM3 and to introduce putatively deleterious variants or reference controls. Cells were cultured and 3' RNA-seq was performed in triplicates.