YWHAZ encodes an adapter protein 14–3-3ζ, which is involved in many signaling pathways that control cellular proliferation, migration, and differentiation. It has not been definitely correlated to any phenotype in OMIM. To investigate the role of YWHAZ gene in intellectual disability and global developmental delay, we conducted whole-exon sequencing in all of available members from a large three-generation family and we discovered that a novel variant of the YWHAZ gene was associated with intellectual disability and global developmental delay. This variant is a missense mutation of YWHAZ, p.Lys49Asn/c.147A > T, which was found in all affected members but not found in other unaffected members. We also conducted computational modeling and knockdown/knockin with Drosophila to confirm the role of the YWHAZ variant in intellectual disability. Computational modeling showed that the binding energy was increased in the mutated protein combining with the ligand indicating that the c147A > T variation was a loss-of-function variant. Cognitive defects and mushroom body morphological abnormalities were observed in YWHAZ c.147A > T knockin flies. The YWHAZ knockdown flies also manifested serious cognitive defects with hyperactivity behaviors, which is consistent with the clinical features. Our clinical and experimental results consistently suggested that YWHAZ was a novel intellectual disability pathogenic gene.

IntroductionWith the advent of trio-based whole-exome sequencing, the identification of epilepsy candidate genes has become easier, resulting in a large number of potential genes that need to be validated in a whole-organism context. However, conducting animal experiments systematically and efficiently remains a challenge due to their laborious and time-consuming nature. This study aims to develop optimized strategies for validating epilepsy candidate genes using the Drosophila model.MethodsThis study incorporate behavior, morphology, and electrophysiology for genetic manipulation and phenotypic examination. We utilized the Gal4/UAS system in combination with RNAi techniques to generate loss-of-function models. We performed a range of behavioral tests, including two previously unreported seizure phenotypes, to evaluate the seizure behavior of mutant and wild-type flies. We used Gal4/UAS-mGFP flies to observe the morphological alterations in the brain under a confocal microscope. We also implemented patch-clamp recordings, including a novel electrophysiological method for studying synapse function and improved methods for recording action potential currents and spontaneous EPSCs on targeted neurons.ResultsWe applied different techniques or methods mentioned above to investigate four epilepsy-associated genes, namely Tango14, Klp3A, Cac, and Sbf, based on their genotype-phenotype correlation. Our findings showcase the feasibility and efficiency of our screening system for confirming epilepsy candidate genes in the Drosophila model.DiscussionThis efficient screening system holds the potential to significantly accelerate and optimize the process of identifying epilepsy candidate genes, particularly in conjunction with trio-based whole-exome sequencing.

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.

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