Chromosome 6 mutation in the gene for laforin. Laforin is an intracellular protein tyrosine phosphatase. Maternal inheritance from mitochondrial DNA mutation. Myoclonic epilepsy, mitochondrial myopathy, ataxia, deafness, and dementia. Affected gene codes for tRNA Lys , a mitochondrial transfer RNA that carries lysine into the translational process.
Protein synthesis is impaired at lysine residues.
This results in a premature termination of polypeptides. Affected mitochondria have impaired oxidative phosphorylation. Glutamate requires transport out of the cells. Loss of energy may causes excitotoxicity and neuronal hyperexcitability. Neuronal ceroid lipofuscinosis Accumulation of autofluorescent inclusions that resemble ceroid and lipofuscin in neurons.