Last update: 12/12/2007
Background to disease
Main referral types:
1) Lebers Hereditary Optic Neuropathy (LHON): OMIM #535000
2) Neuropathy, Ataxia and Retinitis Pigmentosa (NARP) `` OMIM #551500 (gene OMIM #516060)
3) Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis and Stroke-Like Episodes (MELAS) OMIM #540000 (gene OMIM #590050)
4)` Myoclonus Epilepsy associated with Ragged Red Fibres (MERRF) OMIM #545000 (gene OMIM #590060)
5) Deafness Not GENLYNC (see note below) - see Deafness page OMIM #520000 (gene OMIM #221745)
A human cell contains thousands of copies of mitochondrial DNA (mDNA) but the total mDNA complement represents 0.5% of the total DNA in a nucleated cell. The double stranded circular mDNA genome is 16,569bp long. The mDNA encodes 37 genes, of which 22 code for mitochondrial tRNA molecules and 2 for mitochondrial rRNA molecules involved in mitochondrial protein synthesis. The remaining 13 code for polypeptides involved in the mitochondrial oxidative phosphorylation system. Inheritance of mitochondria are exclusively maternal.
Mitochondrial Disease |
Gene(s) affected |
Common mutations |
|
LHON |
NADH dehydrogenase genes (ND1, ND4, ND6) |
3460G>A, 11778G>A, 14484T>C |
|
NARP |
ATPase6 subunit |
8993T>G, 8993T>C |
|
MELAS |
tRNAleu gene |
3243A>G |
|
MERRF |
T j loop of the tRNAlys gene |
8344A>G |
Mitochondrial deafness testing is also available (see Deafness page)
Laboratory Analysis
Analysis for this disease is now carried out by the Northern Genetics Service under a reciprocal arrangement (GENLYNC). Please contact them directly regarding information regarding turnaround time and sensitivity. Local samples should still be sent via the Yorkshire Regional Genetic Laboratory where they will be forwarded as whole blood as appropriate. DNA from these samples can be stored in the Yorkshire Regional Genetic Laboratory if it is anticipated that future tests may be required (please indicate clearly on referral card if required).