Biomedical subjects

Roel Smeets

Publications and source records attributed to Roel Smeets.

4 recordsLinked to original sources

PubMed2006

Mutated ND2 impairs mitochondrial complex I assembly and leads to Leigh syndrome.

We describe a novel mitochondrial ND2 mutation (T4681C) in a patient presenting with Leigh Syndrome. Biochemical analyses revealed a low isolated complex I activity in patient's fibroblasts, blood and skeletal muscle. Mutant transmitochondrial cybrid clones retained the specific complex I defect, demonstrating the mitochondrial genetic origin of the disease. The mutation leads to a L71P substitution at an evolutionary conserved amino acid stretch. By two-dimensional blue native electrophoresis (2D-BN-SDS-PAGE), decreased complex I levels were observed together with an accumulation of specific assembly intermediates, suggesting that the mutation disturbs the complex I assembly pathway.

Amino Acid Sequence↗

PubMed2003

Leigh syndrome due to compound heterozygosity of dihydrolipoamide dehydrogenase gene mutations. Description of the first E3 splice site mutation.

UNLABELLED: A boy with recurrent episodes of hypoglycaemia and ataxia, microcephaly, mental retardation, permanent lactic acidaemia, intermittent 2-oxoglutaric aciduria as well as elevation of serum branched chain amino acids was diagnosed with dihydrolipoamide dehydrogenase (E3) deficiency. Analysis of genomic DNA revealed compound heterozygosity for two novel mutations: I393T in exon 11, located at the interface domain of the protein and possibly interfering with its dimerisation, and IVS9+1G>A located at a consensus splice site. A heterozygous polymorphism was also detected. In the patient's cDNA the I393T mutation and the polymorphism appeared to be homozygous, indicating that the mRNA coming from the IVS9+1G>A mutant allele is not stable. CONCLUSION: as opposed to the non-neurological phenotype of patients with a homozygous G229C mutation, this patient developed Leigh syndrome. Dihydrolipoamide dehydrogenase and pyruvate dehydrogenase complex activities in muscle were 29% and 14% of the lowest control values, respectively. Pyruvate dehydrogenase complex activity in fibroblasts was normal, however, indicating that the biochemical examination of defects in energy metabolism should be performed in a more energy demanding tissue.

Child, Preschool↗

PubMed2003

Impaired complex I assembly in a Leigh syndrome patient with a novel missense mutation in the ND6 gene.

We describe a novel mutation in the ND6 gene (T14487C) in a patient with Leigh syndrome. Biochemical analyses indicated a low complex I activity in the patient's fibroblasts but normal values in muscle and liver. Cybrid clones showed a specific complex I defect that correlates with the mutant heteroplasmy levels. Additionally, we demonstrate an altered mobility and a decrease in the levels of fully assembled complex I in the patient's fibroblasts and cybrids, suggesting that the mutation has a profound effect on complex I assembly and/or stability.

Cells, Cultured↗

PubMed2002

CIA30 complex I assembly factor: a candidate for human complex I deficiency?

The human mitochondrial NADH:ubiquinone oxidoreductase (complex I), the first complex of the oxidative phosphorylation system, is composed of at least 42 subunits. Little is known about the assembly process of these subunits into the mature complex. Recently, two proteins in Neurospora crassa have been found to be involved in the assembly of complex I. These proteins are not constituent parts of the mature complex but are associated with smaller intermediate complexes of the assembly process and have a chaperone-like function. We have characterized the human homologue of one of these two complex I intermediate associated proteins, named CIA30, and show that expression of the human CIA30 protein is ubiquitous with a slightly higher expression in various heart tissues, kidney, lung and liver. As deletion of the Neurospora crassa CIA genes results in severe disruption of the assembly process, human CIA30 can be considered as a candidate gene related to complex I deficiency. Thirteen patients with an isolated complex I deficiency, but who were ruled out for mutations in the 35 nuclear genes of the complex and mtDNA, were subjected to mutational analysis of the gene coding for the human CIA30 protein. Four new single nucleotide polymorphisms (SNPs) were detected but no functional mutation was found.

Amino Acid Sequence↗