Zuluaga-Forero, Maximiliano et al. (2021) International Worm Meeting "Novel patient-derived mutation in the presynaptic calcium channel UNC-2 reduces synaptic expression yet increases presynaptic release"

Kurshan, Peri T., Dong, Yongming, Bai, Jihong, Zuluaga-Forero, Maximiliano

[International Worm Meeting, 2021]

Channelopathies cause a wide variety of disorders, but understanding how specific mutations lead to disease has been complicated by gene redundancy and compensatory effects in various classical and complex vertebrate models. We use C. elegans to evaluate the functional and behavioral effect of a rare and novel human patient-derived point mutation (D1634N) in the P/Q-type voltage-gated calcium channel (CACNA1). Mutations in this channel are typically associated with autosomal dominant neurological disorders like familial hemiplegic migraine type 1 (FHM1), episodic ataxia type 2 (EA-2), and Spinocerebellar ataxia type 6 (SCA6); however, patients with the D1634N mutation have not been classified into any of these disorders, suggesting a novel mechanism of action. The worm has only one ortholog of the channel (UNC-2) expressed in its nervous system and shares high homology in the region of the single point mutation D1634N. Our CRISPR-generated D1634N worms show decreased channel expression at synapses using an endogenously-tagged protein. Surprisingly, acetylcholine release (as assessed by aldicarb sensitivity), miniature EPSC frequency, and behavioral readouts of hyperactivity are all increased, suggesting that this point mutation may affect channel voltage sensitivity and/or sub-synaptic localization at presynapses. Additional interactions with other presynaptic proteins and calcium channel auxiliary subunits are being evaluated to address the impact of this mutation on presynaptic morphology and synaptic function.