Retinitis pigmentosa (RP) is a rare, heterogenic, and hereditary disease that produces gradual loss of the visual field and can cause blindness. Mutations causing the disease are still unknown in about 50% of the cases. By CRISPR, we mimicked a few RP mutations in splicing-related genes such as PRPF8/prp-8 and SRNPN200/snpr-200 (Kukhtar et al, 2020). One of the alleles displaying a strong phenotype was used in a small-scale drug screen to identify small molecules capable of alleviating the phenotype. Unexpectedly, we found an FDA-approved drug having a detrimental effect on some of the mutant strains. Since RP onset and progression are highly variable due to environmental or genetic modifiers, C. elegans could help RP prognosis by identifying such modifiers. We performed an RNAi screen on RP mutants with no overt phenotypes and found synthetic interactions with other splicing-related genes. Thus, secondary mutations in these genetic interactors could act as modifiers of the course of the disease. We are taking steps towards establishing C. elegans as an RP diagnosis model by evaluating the functional impact of potential RP mutations, or variants of unknown significance (VUS), in worms. For that purpose, we are setting a panel of features associated with splicing-related RP mutations, including a genetic interaction with a CRISPR-edited Slow Polymerase II mutant (
ama-1(
cer135[R743H])), mortal germline, or aberrant splicing events at specific transcripts. We are also humanizing the sequence encoding the splicing factors
prp-3 in the endogenous locus to investigate if such humanization is beneficial for functional studies of VUS. Therefore, our RP research line in RP demonstrates the value of C. elegans for investigating rare diseases and for providing valuable information in the search of drugs, diagnosis, and prognosis.