Phosphoribosyl pyrophosphate synthetase-1 (PRPS1) is a key enzyme in nucleotide biosynthesis, and mutations in PRPS1 are found in several human diseases including nonsyndromic sensorineural deafness, Charcot-Marie-Tooth disease-5, and Arts Syndrome. We utilized zebrafish as a model to confirm that mutations in PRPS1 result in phenotypic deficiencies in zebrafish similar to those in the associated human diseases. We found two paralogs in zebrafish, prps1a and prps1b and characterized each paralogous mutant individually as well as the double mutant fish. Zebrafish prps1a mutants and prps1a;prps1b double mutants showed similar morphological phenotypes with increasingly severe phenotypes as the number of mutant alleles increased. Phenotypes included smaller eyes and reduced hair cell numbers, consistent with the optic atrophy and hearing impairment observed in human patients. The double mutant also showed abnormal development of primary motor neurons, hair cell innervation, and reduced leukocytes, consistent with the neuropathy and recurrent infection of the human patients possessing the most severe reductions of PRPS1 activity. Further analyses indicated the phenotypes were associated with a prolonged cell cycle likely resulting from reduced nucleotide synthesis and energy production in the mutant embryos. We further demonstrated the phenotypes were caused by delays in the tissues most highly expressing the prps1 genes.
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We would like to thank Dustin Prebilic, Colin Huck, and their team members at Charles Rivers for animal husbandry; Haigen Huang and Shou Lin for in vitro fertilization of the prps1a viral mutant; Sahlee Sabala from Department of Laboratory Medicine at NIH for Wright Giemsa staining of the blood smear slides; Stephen Wincovitch from NHGRI Cytogenetics and Microscopy Core for assistance in imaging; the members of the Burgess Laboratory for helpful discussions. This research was supported by the Intramural Research Program of the National Human Genome Research Institute (ZIAHG200386-05), the National Eye Institute (EY019267 to L.A.S.), and the National Institute of Dental and Craniofacial Research MinnCResT Training Grant (T32DE07288, T90DE022732 to P.R.P.).