PRRT2 mutations lead to neuronal dysfunction and neurodevelopmental defects

Abstract

Mutations in the proline-rich transmembrane protein 2 (PRRT2) gene cause a wide spectrum of neurological diseases, ranging from paroxysmal kinesigenic dyskinesia (PKD) to mental retardation and epilepsy. Previously, seven PKD-related PRRT2 heterozygous mutations were identified in the Taiwanese population: P91QfsX, E199X, S202HfsX, R217PfsX, R217EfsX, R240X and R308C. This study aimed to investigate the disease-causing mechanisms of these PRRT2 mutations. We first documented that Prrt2 was localized at the pre- and post-synaptic membranes with a close spatial association with SNAP25 by synaptic membrane fractionation and immunostaining of the rat neurons. Our results then revealed that the six truncating Prrt2 mutants were accumulated in the cytoplasm and thus failed to target to the cell membrane; the R308C missense mutant had significantly reduced protein expression, suggesting loss-of function effects generated by these mutations. Using in utero electroporation of shRNA into cortical neurons, we further found that knocking down Prrt2 expression in vivo resulted in a delay in neuronal migration during embryonic development and a marked decrease in synaptic density after birth. These pathologic effects and novel disease-causing mechanisms may contribute to the severe clinical symptoms in PRRT2–related diseases.

The epileptic and nonepileptic spectrum of paroxysmal dyskinesias: Channelopathies, synaptopathies, and transportopathies

“…Its temporal expression increases during the development and in fact PRRT2 silencing in primary neurons decreases synaptic density and alters nerve terminal ultrastructure. Using RNA interference, it has been shown that knocking PRRT2 in mouse embryos leads to a delay in neuronal migration and defects in synaptic development [45]. Therefore, it is not surprising that homo- or heterozygous biallelic PRRT2 mutations can lead to neurodevelopmental disorders [46–48].…”

Dynamin 1 isoform roles in a mouse model of severe childhood epileptic encephalopathy

“…Seizure disorders associated with many of these newly identified mutations manifest in early childhood and are accompanied by serious behavioral comorbidities: SYN1 (Giannandrea et al, 2013; Paemka et al, 2013), STXBP1 (Stamberger et al, 2016), Prrt2 (Liu et al, 2016; Valente et al, 2016), NAPB (Conroy et al, 2016), SV2a. (Serajee and Huq, 2015).…”

PRRT2 missense mutations cluster near C‐terminus and frequently lead to protein mislocalization

“…The procedure was performed according to a previous report . Briefly, HEK293T human embryonic kidney cells were cultured in Dulbecco modified Eagle medium (Life Technologies) with 10% fetal bovine serum.…”

“…Most truncating variants of PRRT2 lead to a shortened protein that lacks both C‐terminal TM domains. Previous functional studies have confirmed that truncated PRRT2 failed to localize to the plasma membrane and distributed in the cytoplasm and sometimes in the nucleus . Thus, mislocalization of PRRT2 mutations may lead to the loss of its normal functions at the synapses .…”