Abstract 12395: Knockdown of Murine Ndufs6 Expression Causes Mitochondrial Complex I Deficiency-Specific Cardiomyopathy and Left Ventricular Dysfunction
NADH dehydrogenase ubiquinone iron-sulfur protein subunit 6 (NDUFS6) is crucial to the assembly of mitochondrial respiratory complex I (CI). In human neonates, congenital NDUFS6 mutation causes severe CI-deficiency that is fatal within a few weeks. In order to determine the extent of molecular and functional consequences of CI-deficiency, mice were generated with knockdown of Ndufs6 (Ndufs6^gt/gt). Using Gene-Trap embryonic stem cells, a tetramer fusion protein of the Ndufs6 subunit was produced preventing correct assembly of CI. With only 1-34% of wildtype (WT) mRNA evident in all Ndufs6^gt/gt tissues, protein expression of Ndufs6 was diminished. The most marked decrease of CI occurred in Ndufs6^gt/gt hearts (<10% of CI activity in WT controls). Mitochondria were abnormally shaped with tightly stacked and aligned central cristae. Although other respiratory enzyme complexes had normal activity, ATP synthesis was ~40% of WT levels. Male Ndufs6^gt/gt mice had a normal phenotype and weight gain for ~4 months after which they developed weight loss, progressive cardiac enlargement, and increased gene expression of atrial natriuretic peptide and beta myosin heavy chain. Cohort mortality was 50% at 200 days. On echocardiography, left ventricular dilatation and reduced fractional shortening was evident in Ndufs6^gt/gt from 30 days of age. Frank-Starling relationships were determined in electrically paced (490 bpm), isolated buffer-perfused working heart preparations (50 mmHg afterload). At all levels of left atrial filling examined (5, 10, 15, 20, 25 mmHg), developed pressure, aortic output, coronary flow, stroke volume, rates of contractility and relaxation, and left ventricular external work in Ndufs6^gt/gt hearts were lower than in WT. Thus Ndufs6-specific CI-deficiency promotes cardiomyopathy with limited bioenergetic and cardiac functional reserve capacity. This murine model may permit study of the efficacy of novel therapeutic interventions for CI deficiency states.
- © 2011 by American Heart Association, Inc.