Characterization of a loss-of-function NSF attachment protein beta mutation in monozygotic triplets affected with epilepsy and autism using cortical neurons from proband-derived and CRISPR-corrected induced pluripotent stem cell lines.

We investigated whether a homozygous recessive genetic variant of NSF attachment protein beta (NAPB) gene inherited by monozygotic triplets contributed to their phenotype of early-onset epilepsy and autism. Induced pluripotent stem cell (iPSC) lines were generated from all three probands and both parents. The NAPB genetic variation was corrected in iPSC lines from two probands by CRISPR/Cas9 gene editing. Cortical neurons were produced by directed, in vitro differentiation from all iPSC lines. These cell line-derived neurons enabled us to determine that the genetic variation in the probands causes exon skipping and complete absence of NAPB protein. Electrophysiological and transcriptomic comparisons of cortical neurons derived from parents and probands cell lines indicate that loss of NAPB function contributes to alterations in neuronal functions and likely contributed to the impaired neurodevelopment of the triplets.

Generation of induced pluripotent stem cell lines from nonaffected parents and monozygotic triplets affected with autism spectrum disorder and epilepsy.

We have generated induced pluripotent stem cell (iPSC) lines from monozygotic triplets with a rare homozygous mutation in NAPB gene (c.354+2T>G). iPSC lines were also generated from their consanguineous parents who were both heterozygous for the inherited NAPB mutation. The iPSC lines were generated using non-integrating Sendai viral vectors. All iPSC lines showed prototypical stem cell morphology, expressed pluripotency markers and were able to differentiate to all three germ lineages. These iPSC lines will be useful to explore the molecular function of NAPB in neurophysiology and how its dysfunction potentially contributes to the progression of neurodevelopmental disorders associated with autism and epilepsy.