A homozygous variant in mitochondrial RNase P subunit PRORP is associated with Perrault syndrome characterized by hearing loss and primary ovarian insufficiency

Perrault syndrome is a rare autosomal recessive condition characterised by sensorineural hearing loss in both sexes and primary ovarian insufficiency in 46 XX, females. It is genetically heterogeneous with biallelic variants in six genes identified to date ( HSD17B4, HARS2, LARS2, CLPP, C10orf2 and ERAL1 ). Most genes possessing variants associated with Perrault syndrome are involved in mitochondrial translation. We describe a consanguineous family with three affected individuals homozygous for a novel missense variant c.1454Cu003eT; p.(Ala485Val) in KIAA0391 , encoding proteinaceous RNase P (PRORP), the metallonuclease subunit of the mitochondrial RNase P complex, responsible for the 5′-end processing of mitochondrial precursor tRNAs. In RNase P activity assays, RNase P complexes containing the PRORP disease variant produced ~35-45% less 5′-processed tRNA than wild type PRORP. Consistently, the accumulation of unprocessed polycistronic mitochondrial transcripts was observed in patient dermal fibroblasts, leading to an observable loss of steady-state levels of mitochondrial oxidative phosphorylation components. Expression of wild type KIAA0391 in patient fibroblasts rescued tRNA processing. Immunohistochemistry analyses of the auditory sensory epithelium from postnatal and adult mouse inner ear showed a high level of PRORP in the efferent synapses and nerve fibres of hair cells, indicating a possible mechanism for the sensorineural hearing loss observed in affected individuals. We have identified a variant in an additional gene associated with Perrault syndrome. With the identification of this disease-causing variant in KIAA0391 , reduced function of each of the three subunits of mitochondrial RNase P have now been associated with distinct clinical presentations.