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In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila
Published on: August 20, 2019
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Uncovering functional insights into human pathogenic variants in CDK19 using Drosophila models
Karampal S Grewal1,2, Christopher Tam1,2, Jenny Z Liao1,2
1Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, B.C. V5A 1S6, Canada.
Human Molecular Genetics
|November 18, 2025
Summary
Two CDK19 variants linked to Developmental and Epileptic Encephalopathy-87 (DEE87) were studied in fruit flies. One variant (Y32H) showed function, while the other (T196A) appeared to be a loss of function.
Area of Science:
- Genetics
- Neuroscience
- Developmental Biology
Background:
- Heterozygous missense variants in CDK19 are associated with Developmental and Epileptic Encephalopathy-87 (DEE87), characterized by global developmental delay, intellectual disability, and neuromuscular issues.
- Previous studies proposed conflicting functions (loss-of-function vs. gain-of-function) for CDK19 variants Y32H and T196A based on Drosophila models.
Purpose of the Study:
- To functionally evaluate the dominant missense variants Y32H and T196 in CDK19 within Drosophila models of DEE87.
- To elucidate the precise functional nature of these variants and their implications for DEE87 pathogenesis.
Main Methods:
- Utilized Drosophila melanogaster models with RNA interference (RNAi)-mediated depletion of endogenous cdk8 (ortholog of human CDK8/CDK19).
- Expressed wild-type and variant human CDK19 (Y32H, T196A) in the cdk8-depleted fly background to assess functional rescue of observed phenotypes.
- Administered antioxidant supplementation to evaluate its effect on T196A variant phenotypes.
Main Results:
- Depletion of Drosophila cdk8 resulted in muscle myofibril thickening, mitochondrial fusion, and impaired climbing ability.
- Wild-type human CDK19 expression rescued these defects, confirming functional conservation.
- The Y32H variant demonstrated rescue capabilities, suggesting functional activity, whereas T196A failed to rescue, indicating a potential loss of function.
- Antioxidant treatment ameliorated T196A-associated phenotypes in the fly model.
Conclusions:
- The study provides a detailed functional characterization of CDK19 variants Y32H and T196A in a conserved Drosophila model.
- Results suggest Y32H may retain function, while T196A exhibits loss-of-function characteristics, potentially influenced by oxidative stress.
- These findings offer translational insights into DEE87 mechanisms and potential therapeutic avenues.
