Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0162671 (MELAS)
 587 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Because Wolfram (or DIDMOAD) syndrome is supposed to be a mitochondrial (mt)-mediated disease, we investigated a group of eight DIDMOAD patients with respect to point mutations of the mtDNA thus far described as being associated with defined mitochondrial disorders such as MELAS, MERRF, and LHON. Furthermore, to screen DIDMOAD patients for other mtDNA defects we used Southern blot analysis to detect mtDNA length mutations and rearrangements as well as PCR-SSCP and direct sequencing to screen all ND genes (complex I of the respiratory chain), the 22 tRNAs, and a part of the cyt b gene for unknown mutations. As a disease control group, 17 LHON patients (harboring one of the primary LHON mutations) were included in this study because of the overlapping clinical symptoms (optic atrophy) in both syndromes. We compared mtDNA variants identified in DIDMOAD patients with those found in LHON patients as well as in a control group consisting of 67 healthy German blood donors. In total, the control group was characterized by 29 polymorphic sites in ND and tRNA genes that define certain major Caucasian haplotypes. We found that a cluster of nucleotide exchanges at nucleotide positions (nps) 4216 and 11,251 roughly discriminates controls (12/67 controls, 18%) from the disease groups (6/8 DIDMOAD patients, 75%; 10/17 LHON patients, 59%). All 4216-positive LHON patients (10 patients) were concentrated in a haplogroup defined by additional exchanges at nps 10,398, 12,612, and 13,708 (haplogroup A), while the bulk of 4216-positive DIDMOAD patients (5 patients) were found in a distinct haplogroup consisting of nucleotide exchanges at nps 4917, 10,463, 13,368, 14,233, and 15,928. The frequencies of both haplogroups were significantly lower in the control group versus the respective disease groups. A more detailed analysis was performed by sequencing the two hypervariable regions of the non-coding D-loop region from patients and controls and corroborated the ranging in the two major haplogroups. Thus, the different clinical features of the mitochondrial disease groups investigated here corresponded to different clusters of mtDNA variants, which might act as predisposing haplotypes, increasing the risk for disease.
 ...
PMID:Wolfram (DIDMOAD) syndrome and Leber hereditary optic neuropathy (LHON) are associated with distinct mitochondrial DNA haplotypes. 902 81

Mitochondrial (mt)DNA haplogroups in a German control group (n = 67) were characterized by screening mitochondrial coding regions encompassing most of the ND, tRNA and cyt b genes. We used a PCR-SSCP screening approach followed by direct sequencing of polymorphic mtDNA fragments. Five major mtDNA lineages, diverging in at least nine different haplogroups, could be defined by characteristic polymorphic sites in mitochondrial genes. Additional sequencing of two hypervariable segments (HVS-I and II) of the non-coding displacement (D) loop in all control subjects revealed that certain D loop variants were strongly correlated with lineages and haplogroups, while others represented hotspots occurring frequently in different haplogroups. The existence of identified lineages and haplogroups received support from data in the literature, obtained by use of different approaches. Subsequently, we investigated four disease groups for association with these haplogroups: (i) LHON patients (n = 55) carrying at least one of the primary/intermediate LHON mutations at nt 3460, 11778, 14484 and/or 15257; (ii) patients suffering from Wolfram or DIDMOAD syndrome (n = 8); (iii) MELAS patients (n = 9); (iv) a group of children, who died from 'sudden infant death syndrome' (SIDS) (n = 9). The distribution patterns among the haplogroups of the disease groups (LHON, DIDMOAD and SIDS) differed considerably from the control population. LHON and DIDMOAD were significantly under-represented in the most frequent German haplogroup DC, but were concentrated in a mtDNA lineage defined by polymorphisms at nt 4216 + 11251 + 16126. As this lineage diverged into two precisely defined haplogroups, LHON and DIDMOAD could be assigned to the two haplogroups separately. Strikingly, SIDS was often found in association with two rare German haplogroups. MELAS patients were equally distributed among German haplogroups and, moreover, did not reveal any accumulation of specific D loop variants. We conclude that certain European mtDNA haplogroups define a genetic susceptibility basis for various disorders.
 ...
PMID:Population genetics and disease susceptibility: characterization of central European haplogroups by mtDNA gene mutations, correlation with D loop variants and association with disease. 930 61

Mutations in the mitochondrial tRNA(leu) (UUR) gene have been associated with diabetes mellitus and deafness. We screened for the presence of mtDNA mutations in the tRNA(leu) (UUR) gene and adjacent ND1 sequences in 12 diabetes mellitus pedigrees with a possible maternal inheritance of the disease. One patient carried a G to A substitution at nt 3243 (tRNA(leu) (UUR) gene) in heteroplasmic state. In a second pedigree a patient had an A to G substitution at nt 3397 in the ND1 gene. All maternal relatives of the proband had the 3397 substitution in homoplasmic state. This substitution was not present in 246 nonsymptomatic Caucasian controls. The 3397 substitution changes a highly conserved methionine to a valine at aa 31 and has previously been found in Alzheimer's (AD) and Parkinson's (PD) disease patients. Substitutions in the mitochondrial ND1 gene at aa 30 and 31 have associated with a number of different diseases (e.g. AD/PD, MELAS, cardiomyopathy and diabetes mellitus, LHON, Wolfram-syndrome and maternal inherited diabetes) suggesting that changes at these two codons may be associated with very diverse pathogenic processes. In a further attempt to search for mtDNA mutations outside the tRNAleu gene associated with diabetes, the whole mtDNA genome sequence was determined for two patients with maternally inherited diabetes and deafness. Except for substitutions previously reported as polymorphisms, none of the two patients showed any non-synonymous substitutions either in homoplasmic or heteroplasmic state. These results imply that the maternal inherited diabetes and deafness in these patients must result from alterations of nuclear genes and/or environmental factors.
 ...
PMID:MtDNA mutations in maternally inherited diabetes: presence of the 3397 ND1 mutation previously associated with Alzheimer's and Parkinson's disease. 1203 16