Clinically severe CACNA1A alleles affect synaptic function and neurodegeneration differentially
Xi Luo1, Jill A Rosenfeld1, Shinya Yamamoto1,2
1Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States of America.
Plos Genetics
|July 26, 2017
Summary
Dominant CACNA1A mutations cause neurological disorders. A novel R1673P variant leads to neurodegeneration via toxic gain-of-function, while R1664Q shows loss-of-function.
Area of Science:
- Neuroscience
- Genetics
- Molecular Biology
Background:
- Dominant mutations in CACNA1A, encoding a key calcium channel subunit, are linked to various neurological conditions.
- Severe early-onset developmental delay and ataxia can arise from de novo CACNA1A missense alleles, particularly those affecting transmembrane segments.
Observation:
- Exome sequencing identified a novel CACNA1A variant (p.R1673P) in a patient with global developmental delay and cerebellar atrophy.
- A recurrent variant (p.R1664Q) was found in four individuals with developmental delay, hypotonia, and ophthalmologic issues.
- Functional studies in Drosophila were performed using conserved point mutations in the cac gene, the fly homolog of CACNA1A.
Findings:
- The p.R1673P mutant failed to rescue cac lethality and demonstrated gain-of-function in electroretinograms, leading to neurodegeneration in aging flies.
- The p.R1664Q variant exhibited loss-of-function and did not cause neurodegeneration.
- These findings suggest the R1673P allele induces neurodegenerative phenotypes through a toxic gain-of-function mechanism.
Implications:
- The novel R1673P CACNA1A allele contributes to severe neurodevelopmental disorders and progressive cerebellar atrophy.
- Understanding the gain-of-function mechanism of R1673P may reveal new therapeutic targets for related neurological diseases.
- This study highlights the utility of Drosophila models for investigating the functional impact of human neurological disease-associated variants.
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