Ndufa9 Conditional Knockout mouse models

Ndufa9, ortholog of human NDUFA9, encodes the 39 kDa accessory subunit of complex I, a short-chain dehydrogenase and reductase family fold that binds NADPH as a structural cofactor and packs against the core subunits forming the quinone chamber, stabilizing the junction between peripheral and membrane arms during assembly. Human biallelic variants cause severe neonatal lactic acidosis, Leigh syndrome or fatal infantile cardiomyopathy, and cell models show loss of holoenzyme with accumulation of Q module intermediates, indicating an assembly rather than catalytic mechanism. Because the human alleles are largely hypomorphic missense affecting NADPH binding or protein stability, knocking in the specific residue changes gives a graded, interpretable model, whereas a conditional null establishes maximal tissue dependence and is best deployed with inducible Cre in heart or brain. No paralogous subunit compensates. Match allele to endpoint, using complexome profiling, NADPH binding assays on purified enzyme, respirometry, blood and cerebrospinal fluid lactate, and cardiac imaging.

Tissue restricted knockout of Ndufa9 keeps wild type function everywhere else. Breeding is often more robust, and the setup mirrors patient biology where mutations arise in a subset of cells.