Abstract
We have created a mouse model with an isolated cytochrome
c
oxidase (COX) deficiency by disrupting the
COX10
gene in skeletal muscle. Missense mutations in
COX10
have been previously associated with mitochondrial disorders. Cox10p is a protoheme:heme-
O
-farnesyl transferase required for the synthesis of heme
a
, the prosthetic group of the catalytic center of COX.
COX10
conditional knockout mice were generated by crossing a LoxP-tagged
COX10
mouse with a transgenic mouse expressing cre recombinase under the myosin light chain 1f promoter. The
COX10
knockout mice were healthy until approximately 3 months of age when they started developing a slowly progressive myopathy. Surprisingly, even though COX activity in
COX10
KO muscles was <5% of control muscle at 2.5 months, these muscles were still able to contract at 80–100% of control maximal forces and showed only a 10% increase in fatigability, and no signs of oxidative damage or apoptosis were detected. However, the myopathy worsened with time, particularly in female animals. This
COX10
KO mouse allowed us to correlate the muscle function with residual COX activity, an estimate that can help predict the progression pattern of human mitochondrial myopathies.
