Investigating the effect of PURA missense variants on neurodevelopment in X. tropicalis frogs using CRISPR base editing

PURA is a gene that encodes a DNA and RNA-binding protein with multiple functions that is essential for successful neurodevelopment in vertebrates. Spontaneous genetic variants in PURA cause a severe neurodevelopmental disorder in humans, PURA syndrome, characterised by intellectual disability, muscle weakness and other, variable symptoms. These genetic variants span the length of the PURA protein, but no strong correlation has been found between the type and localisation of these variants and the presence or severity of patient symptoms. This limits prediction of patient prognosis and the scope of therapy design.

Xenopus frogs have been estimated to share almost 80% of all known human disease genes, including PURA. Knockout of frog pura in X. tropicalis produces a clear neurodevelopmental phenotype, effecting morphology, survival and working memory in the resulting tadpoles. To determine their effect on neurodevelopment, PURA missense variants from medical genomics databases and the literature will be precisely recreated in X. tropicalis frogs using CRISPR base editing. By comparison with AI-generated variant effect predictions, phenotypic effects of pura missense variants in Xenopus frogs will then be used to determine the accuracy of the AI tools, and to further our understanding of the relationship between the position and nature of the change in the protein and symptom severity in PURA syndrome.