Global developmental delay and focal seizures in individuals with de novo truncating MACF1 variants.

BACKGROUND: Microtubule and actin crosslinking factor 1 (MACF1) plays a critical role in cytoskeletal regulation. Pathogenic variants in MACF1 are associated with a heterogeneous range of phenotypes, including epilepsy, intellectual disability, developmental delay, brain malformations, and hypotonia. This study aims to report two novel MACF1 variants and further explore the genotype-phenotype correlations and pathogenic mechanisms of MACF1-related disorders. RESULTS: We identified two Chinese patients with de novo heterozygous MACF1 variants. Patient 1 carried a frameshift variant (c.18699_18700del, p.V6234Dfs*2) in the spectrin repeats domain (SRD) and presented with global developmental delay. Patient 2 harbored a nonsense variant (c.19657 C > T, p.Q6533*), also located in the SRD. This patient exhibited focal seizures that were readily controlled with valproic acid and perampanel, along with borderline intelligence, oppositional behavior, and hyperactivity. A review of the literature indicated that variants linked to neuropsychiatric disorders tend to cluster within the SRD, likely acting through a loss-of-function (LoF) mechanism and as risk factors for these type of disorders. Furthermore, the two truncating MACF1 variants we reported most likely act through haploinsufficiency. CONCLUSIONS: Our findings broaden the phenotypic spectrum of MACF1-associated disorders and provide additional evidence for genotype-phenotype correlations. The results also support the role of haploinsufficiency as a possible pathogenic mechanism in de novo MACF1 variants.