Box 1: Areas for future development
- GENETIC COUNSELLING – There are currently no statistically-derived genetic counselling guidelines for mtDNA disease. A multi-national consortium is currently collecting data, and robust guidelines should become available in the next few years when a large cohort has been assembled.
- NUCLEAR–MITOCHONDRIAL INTERACTIONS – By studying relatively rare mitochondrial disorders we will increase our understanding of the way that mitochondria interact with cellular metabolism and particularly the cell nucleus. It is likely that this will have a broader relevance for other neurological diseases.
- ANIMAL MODELS – We currently do not have a good model for heteroplasmic mtDNA point mutation disorders (such as "MELAS" or "MERRF" – see table 2), but there is considerable effort worldwide to generate the model. Many of the unanswered questions about genotype and phenotype can be addressed when the model becomes available, and it may be used to test new treatments.
- NOVEL TREATMENTS – There are currently no treatments for mitochondrial disease, but various avenues show promise, and are likely to enter clinical practice within the next decade (see text).
- ENVIRONMENTAL/EXTERNAL FACTORS – Although it is generally accepted that exogenous factors influence mitochondrial function in humans, identifying them is proving difficult. Population based studies and the further investigation of animal models are likely to provide some insight. If these exogenous factors can be changed (by dietary or pharmacological manipulation), this approach may open up avenues for new treatments.