Abstract
Purpose :
CACNA1F encodes a voltage-dependent L-type calcium channel associated with IRD. We hypothesize that defects associated with mutations in CACNA1F that cause decreased protein production lead to degeneration. 14 unrelated patients with congenital stationary night blindness, Aland Island eye disease, cone-rod dystrophy, and macular degeneration harboring a VUS in CACNA1F were identified.
Methods :
All procedures adhered to the Declaration of Helsinki and were approved by institutional ethics review boards. Exclusion criteria included confounding diagnoses such as autoimmune retinopathy, age-related macular degeneration, and history of retinotoxic medications. Following IRD diagnosis, patient samples were collected for third party genetic testing. Alternative splicing was predicted using SpliceFinder, MaxEntScan, NNSPLICE, GeneSplicer, and Ex-Skip (Alamut Visual Plus). Pathogenesis of identified variants was determined by the consequences of the change including amino acid substitution, evolutionary conservation, presence in a number of reference population databases, and in mutation databases. Fundus images of dilated eyes were acquired with the Optos® camera. Horizontal line scans were obtained with spectral-domain optical coherence tomography.
Results :
8 unique mutations from the 14 patients were identified in CACNA1F. Patients present with retinal mottling and reduction in macular thickness. Variants include c.5128G>T, 2683C>T(p.Arg895*), c.2576+1G>A, c.244C>T, c.2707-2A>G, c.3742-2A>C, and c.370A>G. The variants c.2707-2A>G and c.3742-2A>C are predicted to generate new acceptor sites for splicing. The variant c.370A>G changes an asparagine residue to an aspartic acid at a highly conserved location in the first transmembrane domain.
Conclusions :
Patient phenotypes were consistent with previous reports of CACNA1F-IRD and modeling of mutations from these patients support our hypothesis. Defective splicing is likely to cause changes in the balance of CACNA1F isoforms thereby disrupting the influx of ions at the photoreceptor synaptic terminal, ultimately affecting downstream glutamate release. Ongoing functional studies will further test the molecular mechanisms associated with the mutations in CACNA1F.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.