Expression of Autophagy-Related Proteins in Microlissencephaly Associated with a Novel Variant in the WDR81 Gene.

Abstract

Introduction: Microlissencephaly is a subtype of congenital microcephaly characterized by extreme microcephaly with simplified gyral pattern. Other brain malformations may accompany it. WDR81 encodes a multi-domain transmembrane protein that is predominantly expressed in the brain and is thought to play a role in endolysosomal trafficking and autophagy.

Methods: We reported two siblings with microlissencephaly born to consanguineous Turkish parents and reviewed all previously reported patients with WDR81 variants presenting with severe microcephaly accompanied by congenital brain malformations. Whole-exome sequencing was performed on both siblings. Sanger DNA sequencing was performed on the patients' parents. We also examined LC3, p62, and Beclin 1 mRNA and protein expression levels from blood samples of both siblings using real-time PCR and Western blotting, respectively.

Results: Whole-exome sequencing revealed a novel biallelic c.4157+5G>A splice variant in the WDR81 gene in both siblings. In our study, LC3, p62, and Beclin 1 mRNA expression levels were high, LC3 protein expression level was also high and p62 and Beclin 1 protein expression levels were low.

Conclusion: High LC3 and low p62 protein expression levels supported studies concluding that WDR81 inhibits autophagy through PI3KC3 inhibition, while low Beclin 1 protein expression level supported studies concluding that autophagy is suppressed in case of loss of function variants in the WDR81 gene. We suggest that due to its role in endolysosomal trafficking, WDR81-related diseases should be included in vesicular trafficking disorders.