title: Clear relationship between ETF/ETFDH genotype and phenotype in patients with multiple acyl-CoA dehydrogenation deficiency.
abstract: Mutations in electron transfer flavoprotein (ETF) and its dehydrogenase (ETFDH) are the molecular basis of multiple acyl-CoA dehydrogenation deficiency (MADD), an autosomal recessively inherited and clinically heterogeneous disease that has been divided into three clinical forms: a neonatal-onset form with congenital anomalies (type I), a neonatal-onset form without congenital anomalies (type II), and a late-onset form (type III). To examine whether these different clinical forms could be explained by different ETF/ETFDH mutations that result in different levels of residual ETF/ETFDH enzyme activity, we have investigated the molecular genetic basis for disease development in nine patients representing the phenotypic spectrum of MADD. We report the genomic structures of the ETFA, ETFB, and ETFDH genes and the identification and characterization of seven novel and three previously reported disease-causing mutations. Our molecular genetic investigations of these nine patients are consistent with three clinical forms of MADD showing a clear relationship between the nature of the mutations and the severity of disease. Interestingly, our data suggest that homozygosity for two null mutations causes fetal development of congenital anomalies resulting in a type I disease phenotype. Even minute amounts of residual ETF/ETFDH activity seem to be sufficient to prevent embryonic development of congenital anomalies giving rise to type II disease. Overexpression studies of an ETFB-D128N missense mutation identified in a patient with type III disease showed that the residual activity of the mutant enzyme could be rescued up to 59% of that of wild-type activity when ETFB-D128N-transformed E. coli cells were grown at low temperature. This indicates that the effect of the ETF/ETFDH genotype in patients with milder forms of MADD, in whom residual enzyme activity allows modulation of the enzymatic phenotype, may be influenced by environmental factors like cellular temperature.
authors.affiliation: Research Unit for Molecular Medicine, Aarhus University Hospital and Faculty of Health Sciences, Skejby Sygehus, Aarhus, Denmark. rikke.olsen@mmf.au.dk
authors.forename: Rikke K J
authors.initials: RK
authors.lastname: Olsen
authors.forename: Brage S
authors.initials: BS
authors.lastname: Andresen
authors.forename: Ernst
authors.initials: E
authors.lastname: Christensen
authors.forename: Peter
authors.initials: P
authors.lastname: Bross
authors.forename: Flemming
authors.initials: F
authors.lastname: Skovby
authors.forename: Niels
authors.initials: N
authors.lastname: Gregersen
mesh_terms: D042964:Acyl-CoA Dehydrogenase; D017668:Age of Onset; D017398:Alternative Splicing / Q000235:genetics; D002478:Cells, Cultured; D004252:DNA Mutational Analysis / Q000379:methods; D030541:Databases, Genetic; D004579:Electron Transport / Q000235:genetics; D044927:Electron-Transferring Flavoproteins; D004795:Enzyme Stability / Q000235:genetics; D005091:Exons / Q000235:genetics; D044943:Fatty Acid Desaturases / Q000172:deficiency* / Q000235:genetics*; D005347:Fibroblasts / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D005420:Flavoproteins / Q000235:genetics*; D005838:Genotype; D005977:Glutarates / Q000652:urine; D006801:Humans; D007231:Infant, Newborn; D007506:Iron-Sulfur Proteins; D008661:Metabolism, Inborn Errors / Q000201:enzymology / Q000235:genetics / Q000652:urine; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D000587:Oxidoreductases Acting on CH-NH Group Donors; D010641:Phenotype; D011110:Polymorphism, Genetic / Q000235:genetics; D017510:Protein Folding; D021122:Protein Subunits / Q000235:genetics; D012313:RNA / Q000235:genetics; D013696:Temperature
chemical_list: D044927:Electron-Transferring Flavoproteins; D005420:Flavoproteins; D005977:Glutarates; D007506:Iron-Sulfur Proteins; D009097:Multienzyme Complexes; D021122:Protein Subunits; D012313:RNA; D044943:Fatty Acid Desaturases; D042964:Acyl-CoA Dehydrogenase; D000587:Oxidoreductases Acting on CH-NH Group Donors; C023120:electron-transferring-flavoprotein dehydrogenase; C035736:glutaric acid