Clinically severe CACNA1A alleles affect synaptic function and neurodegeneration differentially.

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.