ZFHX3variants cause childhood partial epilepsy and infantile spasms with favorable outcomes

Abstract

Background: TheZFHX3gene is highly expressed in the developing brain and plays vital roles in embryonic development, cell proliferation, neuronal differentiation, and neuronal death. The association between theZFHX3gene and human disease was undefined. This study aims to explore the relationship betweenZFHX3variants and epilepsy. Methods: Whole-exome sequencing was performed in patients with partial epilepsy without acquired causes.Drosophilamodel ofZfh2(ortholog ofZFHX3) knockdown was used to validate the association betweenZFHX3and epilepsy. The expression level ofZFHX3in different developmental stages was analyzed by using the data in humans from the Brainspan database and in flies and mice determined by RT-qPCR. Results: Eight pairs of compound heterozygous variants inZFHX3were identified in eight unrelated cases of childhood epilepsies. All patients presented partial epilepsy, including two with early spasms and one with frequent nonconvulsive status epilepticus. The three cases with severe epilepsies also had neurodevelopmental abnormities. However, all patients became seizure-free, including the patients with spasms. These variants had no or low allele frequencies in controls and presented statistically higher frequency in the case cohort than the controls. The number of recessiveZFHX3variants identified in this cohort was significantly more than the expected number of the East Asian population and that of the control of 1942 asymptomatic parents. Variants were predicted to be damaging by protein modeling and/or in silico prediction tools. Genotype-phenotype correlation analysis revealed that the patients with missense variants in C-terminus or C-terminus-truncated variant exhibited mild phenotype (only partial epilepsy). Knockdown ofZfh2in flies led to increased susceptibility to seizures and abnormal firing of excitability neurons. InDrosophila, the expression ofZfh2is high in larvae, decreased in pupae and early adults, and increased in later adults. In mice,Zfhx3is predominantly expressed in fetuses and decreased dramatically after birth. In humans, the data from the Brainspan database showed thatZFHX3is highly expressed in the embryonic period and decreased after birth with a nadir at approximately 10 years old. The dramatical decreasing ofZFHX3in early life correlated with the natural course of the illness. Conclusion:ZFHX3variants were potentially associated with partial epilepsy of childhood and infant spasms. The correlation between the outcome and gene expression stage provided insight into the underlying mechanism of the natural course of illness, potentially being helpful in management of the patients.