Subproject 4

Investigating the Pathophysiology and treatment options of ataxia-associated CACNA1A disease variants in Drosophila melanogaster

In the era of unbiased, diagnostic next-generation sequencing, our knowledge of disease-associated sequence variants is rapidly growing, while our functional understanding is greatly lagging behind. This has important implications for rational patient treatment, as for loss- and gain-of-function mutations diametrically opposite interventions are necessary. In addition, genetic evidence alone is often not sufficient in establishing pathogenicity.

In a well characterized German ataxia cohort, we have detected 17 such variants in the CACNA1A gene, encoding the CaV2.1 voltage gated calcium channel. Given the large number of CACNA1A disease associated mutations described to date, we aim to utilize a rapid and powerful genetic model – Drosophila melanogaster – to investigate selected variants. Its highly conserved CACNA1A ortholog cacophony will be used to (1) test the pathogenicity of candidate variants; (2) assess whether the mutations increase or decrease channel activity and (3) perform preliminary pharmacological studies. We will therefore introduce the orthologous mutations into Drosophila and assess their capacity to rescue lethality of animals where no functional wild-type cacophony is present; record electrophysiological properties of these neurons; and test if small molecule drugs can revert such physiological changes, thereby representing the first steps towards ultimately enabling personalized treatments of CACNA1A patients, guided by the precise nature of the underlying mutation.