title: Molecular diagnostics of mitochondrial disorders.
abstract: The mitochondrial respiratory chain (RC) results from the expression of both mitochondrial and nuclear genes. The number of disease-causing mutations in nuclear genes is steadily growing and mitochondrial DNA (mtDNA) deletions and mutations account for no more than 15-20% of pediatric patients. Unfortunately, the disease-causing mutations have been identified for only a small number of patients. Thus, elucidating the genetic bases of RC is both essential for genetic diagnosis of patients and for fundamental knowledge of these disorders. The molecular diagnostics of mitochondrial disorders come under both genetic diagnosis and research. Indeed, identification of a new gene in a specific patient allows to perform genetic diagnosis in other families and identification of mutations in already known disease-causing genes allows to constitute a cohort of patients for further functional studies. Thus, elucidating the genetic bases of RC deficiency is an essential task that needs the use of several appropriate strategies. Fine phenotypage of patients and candidate gene screening is the first step for the constitution of a well-characterized cohort of patients. Genetic mapping has to be used in large families. This approach is greatly enhanced in the case of consanguineous families. The consanguinity of the parents should also lead to test genetic markers surrounding the gene loci rather than to directly sequence several candidate genes. However, the main problem is encountered in the cases of sporadic cases for which no genetic approaches can be developed. In these cases, functional complementation by human chromosomes or cDNA is the only presently available strategy.
authors.affiliation: INSERM U393, Service de Génétique, Hôpital Necker-Enfants Malades, Unite de Recherches sur les, 149 rue de Sèvres, 75015 Paris, France. roetig@necker.fr
authors.forename: Agnès
authors.initials: A
authors.lastname: Rötig
authors.forename: Sophie
authors.initials: S
authors.lastname: Lebon
authors.forename: Elena
authors.initials: E
authors.lastname: Zinovieva
authors.forename: Julie
authors.initials: J
authors.lastname: Mollet
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Sarzi
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Bonnefont
authors.forename: Arnold
authors.initials: A
authors.lastname: Munnich
mesh_terms: D016227:Benzoquinones / Q000378:metabolism; D002467:Cell Nucleus / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D042967:Electron Transport Complex I / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D014450:Electron Transport Complex III / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000235:genetics; D005260:Female; D006801:Humans; D028361:Mitochondrial Diseases / Q000175:diagnosis* / Q000235:genetics*; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009154:Mutation; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods; D012120:Respiration Disorders / Q000175:diagnosis / Q000209:etiology
chemical_list: D016227:Benzoquinones; D004272:DNA, Mitochondrial; C004532:quinone; D003576:Electron Transport Complex IV; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III