Functional Validation of CLDN Variants Identified in a Neural Tube Defect Cohort Demonstrates Their Contribution to Neural Tube Defects.

Amanda I Baumholtz,Valeria Capra,Patrizia De Marco,Aimee K Ryan

doi:10.3389/fnins.2020.00664

Amanda I Baumholtz, Valeria Capra + Show 2 more

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https://doi.org/10.3389/fnins.2020.00664

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Abstract

Neural tube defects (NTDs) are severe malformations of the central nervous system that affect 1–2 individuals per 2,000 births. Their etiology is complex and involves both genetic and environmental factors. Our recent discovery that simultaneous removal of Cldn3, -4, and -8 from tight junctions results in cranial and spinal NTDs in both chick and mouse embryos suggests that claudins play a conserved role in neural tube closure in vertebrates. To determine if claudins were associated with NTDs in humans, we used a Fluidigm next generation sequencing approach to identify genetic variants in CLDN loci in 152 patients with spinal NTDs. We identified eleven rare and four novel missense mutations in ten CLDN genes. In vivo validation of variant pathogenicity using a chick embryo model system revealed that overexpression of four variants caused a significant increase in NTDs: CLDN3 A128T, CLDN8 P216L, CLDN19 I22T, and E209G. Our data implicate rare missense variants in CLDN genes as risk factors for spinal NTDs and suggest a new family of proteins involved in the pathogenesis of these malformations.

Highlights

Neural tube defects (NTDs) [MIM: 182940] are a group of congenital central nervous system malformations that affect the brain and spinal cord, caused by failure of neural tube closure during embryogenesis
We have shown that claudins are required for apical constriction and convergent extension and mutations in CLDN genes may be implicated in both cranial and spinal NTDs
Our study highlights the conserved function of claudins among species in neural tube closure and supports the hypothesis that rare deleterious variants in CLDN genes are significant risk factors for human spinal NTDs

Summary

Introduction

Neural tube defects (NTDs) [MIM: 182940] are a group of congenital central nervous system malformations that affect the brain and spinal cord, caused by failure of neural tube closure during embryogenesis. They have a complex etiology involving both genetic and environmental factors. NTDs are the second most common birth defect with a varying incidence, affecting 1–2 per 2,000 pregnancies in North America post-folic acid fortification, and as high as 20 per 1,000 births in certain regions of China (Chen et al, 2009). There is an urgent need to better understand the underlying pathogenic mechanisms of NTDs, those not prevented by folic acid fortification

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