Using primary fibroblasts containing bi-allelic mutations (p.Tyr565His and p.Glu733Lys; NM_004793.3) within the LONP1 ATPase domain associated with congenital lactic acidosis, muscle weakness, and multiple mitochondrial OXPHOS deficiencies29, we found substantially reduced solubility of mtHSP70, DNAJA3 and OXA1L (Fig. 4d). Here, DNAJA3 is linked to lactic acidosis.