Does polyribonucleotide nucleotidyltransferase (PNPase) mutation affect the energetic metabolism and the microRNA profile in cell and mitochondria

Objectives PNPase is a protein of the intermembrane space, encoded by PNPT1 and involved in RNA mitochondrial import [1]. PNPT1 mutations have been described in patients suffering from a severe neurological disease and combined respiratory chain defect [2]. We hypothesized that PNPAse could play a role in miRNA import [3]. The objective was to compare the miRNA and metabolomic profile from control and PNPT1 mutant fibroblasts. Methodology and Results Fibroblasts from a patient with PNPT1 mutation (c.1160A>G, p.Gln387Arg) and from a control (C) were grown. Comparison of the metabolomic NMR spectra of their culture media suggested that PNPT1 cells had lower glycolysis, TCA and protein synthesis activity than C cells. Total RNA was extracted from whole cells, isolated mitochondria and mitoplasts. The total number of miRNA detected by RT-qPCR in PNPT1 cells was about 6 times lower than in C cells: 47 vs 310 miRNAs but their average expression was higher (p<10-6). Their distribution among mitochondria, mitoplasts and cells was different (p<10-6): in C cells, there was a gradient from mitoplasts (153) to mitochondria (94) whereas in PNPT1 cells, there was no difference (130 vs 126).