Expression of Autophagy-Related Proteins in Microlissencephaly Associated with a Novel Variant in the WDR81 Gene
Hatice Yelda Yalçın1, Ufkay Karabay2,3, Tayfun Cinleti1
1Department of Pediatric Genetics, İzmir Provincal Health Directorate, İzmir City Hospital, Izmir, Turkey.
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.
Insights
A novel splice variant in the WDR81 gene causes microlissencephaly, a severe brain malformation. This finding links WDR81 gene function to endolysosomal trafficking and autophagy, suggesting WDR81-related disorders are vesicular trafficking diseases.
Area of Science:
- Genetics
- Neuroscience
- Cell Biology
Background:
- Microlissencephaly is a severe congenital microcephaly subtype with simplified gyral patterns and potential brain malformations.
- The WDR81 gene encodes a protein crucial for brain endolysosomal trafficking and autophagy.
Purpose of the Study:
- To investigate the genetic basis of microlissencephaly in two siblings with a novel WDR81 variant.
- To analyze the functional impact of the WDR81 variant on autophagy-related protein and mRNA expression.
Main Methods:
- Whole-exome sequencing and Sanger DNA sequencing were used to identify genetic variants.
- Real-time PCR and Western blotting were employed to assess mRNA and protein expression levels of LC3, p62, and Beclin 1.
Main Results:
- A novel biallelic c.4157+5G>A splice variant in the WDR81 gene was identified in both siblings.
- Elevated LC3, p62, and Beclin 1 mRNA levels were observed.
- High LC3 and low p62 and Beclin 1 protein levels indicated altered autophagy pathways.
Conclusions:
- The WDR81 variant disrupts autophagy, potentially through PI3KC3 inhibition and suppression of autophagy.
- WDR81's role in endolysosomal trafficking suggests WDR81-related diseases should be classified as vesicular trafficking disorders.
More Related Videos
Related Concept Videos
01:22Lysosomal Hydrolases
01:27Autophagy
An autophagic pathway consists of a series of signaling events activated in response to diverse stress and physiological conditions such as food deprivation,...