Genotypic and clinical phenotypic analysis of DEPDC5 gene mutations.

Mutations in the DEPDC5 gene are inherited in an autosomal dominant manner and can lead to various clinical phenotypes, including focal seizures. While numerous case reports on DEPDC5 mutations exist, functional validation studies remain scarce. We analyzed seven cases of epilepsy or developmental disorders caused by DEPDC5 mutations, summarizing their clinical manifestations and conducting genetic analysis of the mutation sites. The age of onset in the seven patients ranged from 2 months to 4 years. Six mutation sites were identified, including three nonsense mutations: c.1443del (p.C481X), c.2512 C > T (p.R838X), and c.2620 C > T (p.R874X); one missense mutation: c.1140 C > A (p.F380L); and two splice-site mutations: c.2802-13 C > G (splicing) and c.4034-2 A > G (splicing). Among these, c.2512 C > T (p.R838X) and c.2620 C > T (p.R874X) had been previously reported, while the remaining mutations were novel. Minigene experiments confirmed that the c.4034-2 A > G mutation resulted in a slightly truncated protein.Focal seizures were the predominant symptom in six cases. Among the four patients with nonsense mutations, three (Cases 2, 4, and 5) exhibited drug-resistant epilepsy. Four out of seven patients responded effectively to lacosamide treatment. DEPDC5 mutations can cause focal seizures, with truncating mutations associated with more severe symptoms. Lacosamide may offer better therapeutic outcomes. The intronic mutation c.463 + 4 A > G (splicing) led to protein truncation and was determined to be pathogenic.