De novo variants in UPF1 associated with intellectual disabilities: Human genetic and functional evidences using Drosophila model.

Nonsense-mediated mRNA decay represents a biologic clearing system against aberrant mRNAs harboring nonsense and frameshift mutations and depends on three factors, UPF1, UPF2, and UPF3 (UPF3A, UPF3B). While germline pathogenic variants of UPF3B and UPF2 are known to be associated with neurodevelopmental disorders, germline variants in UPF1 have not been reported, until date, as being associated with any human disorders. Herein, we report two unrelated patients with de novo UPF1 variants.