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Two microcephaly-associated novel missense mutations in CASK specifically disrupt the CASK-neurexin interaction.

Abstract：

:Deletion and truncation mutations in the X-linked gene CASK are associated with severe intellectual disability (ID), microcephaly and pontine and cerebellar hypoplasia in girls (MICPCH). The molecular origin of CASK-linked MICPCH is presumed to be due to disruption of the CASK-Tbr-1 interaction. This hypothesis, however, has not been directly tested. Missense variants in CASK are typically asymptomatic in girls. We report three severely affected girls with heterozygous CASK missense mutations (M519T (2), G659D (1)) who exhibit ID, microcephaly, and hindbrain hypoplasia. The mutation M519T results in the replacement of an evolutionarily invariant methionine located in the PDZ signaling domain known to be critical for the CASK-neurexin interaction. CASKM519T is incapable of binding to neurexin, suggesting a critically important role for the CASK-neurexin interaction. The mutation G659D is in the SH3 (Src homology 3) domain of CASK, replacing a semi-conserved glycine with aspartate. We demonstrate that the CASKG659D mutation affects the CASK protein in two independent ways: (1) it increases the protein's propensity to aggregate; and (2) it disrupts the interface between CASK's PDZ (PSD95, Dlg, ZO-1) and SH3 domains, inhibiting the CASK-neurexin interaction despite residing outside of the domain deemed critical for neurexin interaction. Since heterozygosity of other aggregation-inducing mutations (e.g., CASKW919R) does not produce MICPCH, we suggest that the G659D mutation produces microcephaly by disrupting the CASK-neurexin interaction. Our results suggest that disruption of the CASK-neurexin interaction, not the CASK-Tbr-1 interaction, produces microcephaly and cerebellar hypoplasia. These findings underscore the importance of functional validation for variant classification.

journal_name

Hum Genet

journal_title

Human genetics

authors

LaConte LEW,Chavan V,Elias AF,Hudson C,Schwanke C,Styren K,Shoof J,Kok F,Srivastava S,Mukherjee K

doi

10.1007/s00439-018-1874-3

subject

Has Abstract

pub_date

2018-03-01 00:00:00

pages

231-246

issue

eissn

0340-6717

issn

1432-1203

pii

10.1007/s00439-018-1874-3

journal_volume

137

pub_type

杂志文章

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Two microcephaly-associated novel missense mutations in CASK specifically disrupt the CASK-neurexin interaction.