Novel lissencephaly‐associated DCX variants in the C‐terminal DCX domain affect microtubule binding and dynamics

Abstract

Objective Pathogenic variants in DCX on the X chromosome lead to lissencephaly and subcortical band heterotopia (SBH), brain malformations caused by neuronal migration defects. Its product doublecortin (DCX) binds to microtubules to modulate microtubule polymerization. How pathogenic DCX variants affect these activities remains not fully investigated. Methods DCX variants were identified using whole exome and Sanger sequencing from six families with lissencephaly/SBH. We examined how these variants affect DCX functions using microtubule binding, regrowth, and colocalization assays. Results We found novel DCX variants p.Val177AlafsTer31 and p.Gly188Trp, as well as reported variants p.Arg196His, p.Lys202Met, and p.Thr203Ala. Incidentally, all of the missense variants were clustered on the C‐terminal DCX domain. The microtubule binding ability was significantly decreased in p.Val177AlafsTer31, p.Gly188Trp, p.Lys202Met, and previously reported p.Asp262Gly variants. Furthermore, expression of p.Val177AlafsTer31, p.Gly188Trp, p.Arg196His, p.Lys202Met, and p.Asp262Gly variants hindered microtubule growth in cells. There were also decreases in the colocalization of p.Val177AlafsTer31, p.Thr203Ala, and p.Asp262Gly variants to microtubules. Significance Our results indicate that these variants in the C‐terminal DCX domain altered microtubule binding and dynamics, which may underlie neuronal migration defects during brain development.

Novel lissencephaly-associated NDEL1 variant reveals distinct roles of NDE1 and NDEL1 in nucleokinesis and human cortical malformations

“…HEK293T and U2OS cells were cultured in DMEM (Life Technologies, USA) supplemented with 10% FBS at 37℃ in humidified air containing 5% CO 2 [ 36 , 72 ]. To transfect pEGFP-C1 constructs into cell culture, cells were placed in 6 cm Petri dishes with a density of 70–80%.…”

Phenotypic Variability in Novel Doublecortin Gene Variants Associated with Subcortical Band Heterotopia

“…N-DC specifically binds to assembled microtubules, whereas C-DC binds to both microtubules and unpolymerized tubulin. A recent study indicated that missense variants in the N-DC tend to induce more severe abnormalities compared to the variants in the C-DC [5].…”

DCX variants in two unrelated Chinese families with subcortical band heterotopia: Two case reports and review of literature

“…DCX is located in q22.3-q23 on the X chromosome and encodes the protein doublecortin (DCX). Mutations in DCX cause lissencephaly in hemizygous male patients, whereas lead to SBH in heterozygous female patients [ 2 , 3 ]. DCX mutations are found in 53–84 % of patients with SBH, making DCX more common than PAFAH1B1 and TUBA1A .…”