RESUMO
AIM: To investigate the presence/absence of the Chr-11 tRNA-Lys-CUU gene as a marker for genetic predisposition to Type 2 diabetes mellitus (T2DM). METHODS: We enrolled 122 patients diagnosed with T2DM and 77 non-diabetic individuals. We evaluated clinical and biochemical parameters (body mass index, hypertension, cholesterol levels, glycosylated hemoglobin, triglycerides, etc.), and performed a genotypic profiling of Chr-11 tRNA-Lys-CUU by polymerase chain reaction analyses. RESULTS: Approximately one third of the population lacked Chr-11 tRNA-Lys-CUU. We did not observe a statistically significant association between the presence/absence of Chr-11 tRNA-Lys-CUU and T2DM. CONCLUSION: The genotypic distribution of Chr-11 tRNA-Lys-CUU in our population was consistent to that reported by others. This gene failed as a marker for T2DM predisposition.
Assuntos
Biomarcadores/análise , Cromossomos Humanos Par 11/genética , Diabetes Mellitus Tipo 2/genética , Deleção de Genes , Predisposição Genética para Doença , RNA de Transferência de Lisina/genética , Idoso , Estudos de Casos e Controles , Diabetes Mellitus Tipo 2/epidemiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Espanha/epidemiologiaRESUMO
BACKGROUND: Mutations in the mitochondrial DNA (mtDNA) have been associated with aminoglycoside-induced and nonsyndromic deafness in different populations. In the present study, we investigated the contribution of mutations in mitochondrial genes to the etiology of hearing loss in a Brazilian sample. METHODS: Using mass spectrometry genotyping technology, combined with direct sequencing, 50 alterations previously described in 14 mitochondrial genes were screened in 152 patients with sensorineural hearing loss and in104 normal hearing controls. RESULTS: Fifteen known mitochondrial alterations were detected (G709A, A735G, A827G, G988A, A1555G, T4363C, T5628C, T5655C, G5821A, C7462T, G8363A, T10454C, G12236A, T1291C, G15927A). Pathogenic mutations in MT-RNR1 and MT-TK genes were detected in 3 % (5/152) of the patients with hearing loss. CONCLUSIONS: This study contributed to show the spectrum of mitochondrial variants in Brazilian patients with hearing loss. Frequency of A1555G was relatively high (2.6 %), indicating that this mutation is an important cause of hearing loss in our population. This work reports for the first time the investigation and the detection of the tRNA(Lys) G8363A mutation in Brazilian patients with maternally inherited sensorineural hearing loss.
Assuntos
DNA Mitocondrial/análise , Perda Auditiva Neurossensorial/genética , Mitocôndrias/genética , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Brasil , Estudos de Casos e Controles , DNA Mitocondrial/genética , DNA Mitocondrial/metabolismo , Feminino , Genótipo , Perda Auditiva Neurossensorial/patologia , Humanos , Masculino , Membro 2 do Grupo A da Subfamília 4 de Receptores Nucleares/genética , RNA de Transferência de Lisina/genéticaRESUMO
We identified a double mutation in a patient with chronic progressive external ophthalmoplegia, located in the tRNA(Ala) (m.5628T>C) and tRNA(Lys) (m.8348A>G) genes. Both mutations were previously described separately and considered pathogenic, however the same mutations were also reported as polymorphisms or phenotype modulator. We analyzed the proportion of each mutation in isolated muscle fibers by single fiber-polymerase chain reaction to investigate the contribution of each mutation to mitochondrial deficiency. Our findings demonstrated that the mutations were heteroplasmic in skeletal muscle and both mutations were present in all single muscle fibers. The proportions of the m.5628T>C mutation were not significantly different between normal and cytochrome-c-oxidase (COX) deficient fibers. However, a significant higher proportion of the m.8348A>G mutation was observed in COX deficient fibers. Homoplasmic m.8348A>G was only observed in COX negative fibers. In conclusion, we provide a piece of evidence toward the pathogenicity of the m.8348A>G mutation and suggest that m.5628T>C is probably a neutral polymorphism.
Assuntos
Fibras Musculares Esqueléticas/metabolismo , Oftalmoplegia Externa Progressiva Crônica/genética , Mutação Puntual/genética , RNA de Transferência de Alanina/genética , RNA de Transferência de Lisina/genética , Adulto , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Feminino , Humanos , Mitocôndrias/genética , Mitocôndrias/metabolismo , Oftalmoplegia Externa Progressiva Crônica/metabolismoRESUMO
Myoclonic epilepsy with ragged red fibers (MERRF) is a mitochondrial disease that is characterized by myoclonic epilepsy with ragged red fibers (RRF) in muscle biopsies. The aim of this study was to analyze Brazilian patients with MERRF. Six patients with MERRF were studied and correlations between clinical findings, laboratory data, electrophysiology, histology and molecular features were examined. We found that blood lactate was increased in four patients. Electroencephalogram studies revealed generalized epileptiform discharges in five patients and generalized photoparoxysmal responses during intermittent photic stimulation in two patients. Muscle biopsies showed RRF in all patients using modified Gomori-trichrome and succinate dehydrogenase stains. Cytochrome c oxidase (COX) stain analysis indicated deficient activity in five patients and subsarcolemmal accumulation in one patient. Molecular analysis of the tRNA(Lys) gene with PCR/RFLP and direct sequencing showed the A8344G mutation of mtDNA in five patients. The presence of RRFs and COX deficiencies in muscle biopsies often confirmed the MERRF diagnosis. We conclude that molecular analysis of the tRNA(Lys) gene is an important criterion to help confirm the MERRF diagnosis. Furthermore, based on the findings of this study, we suggest a revision of the main characteristics of this disease.
Assuntos
Músculos/patologia , Músculos/fisiopatologia , Adulto , Biópsia , Análise Química do Sangue , Brasil , DNA Mitocondrial/genética , Eletroencefalografia , Complexo IV da Cadeia de Transporte de Elétrons/análise , Feminino , Histocitoquímica , Humanos , Síndrome MERRF/genética , Síndrome MERRF/patologia , Masculino , Microscopia , Pessoa de Meia-Idade , Mutação Puntual , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , RNA de Transferência de Lisina/genética , Análise de Sequência de DNARESUMO
The complete mitochondrial (mt) genomes of five marsupial species have been sequenced. The species represent all three South American orders (Didelphimorphia, Paucituberculata, and Microbiotheria). Phylogenetic analysis of this data set indicates that Didelphimorphia is a basal marsupial lineage followed by Paucituberculata. The South American microbiotherid Dromiciops gliroides (monito del monte) groups with Australian marsupials, suggesting a marsupial colonization of Australia on two occasions or, alternatively, a migration of an Australian marsupial lineage to South America. Molecular estimates suggest that the deepest marsupial divergences took place 64-62 million years before present (MYBP), implying that the radiation of recent marsupials took place after the K/T (Cretaceous/Tertiary) boundary. The South American marsupial lineages are all characterized by a putatively non-functional tRNA for lysine, a potential RNA editing of the tRNA for asparagine, and a rearrangement of tRNA genes at the origin of light strand replication.
Assuntos
Evolução Biológica , DNA Mitocondrial , Genoma , Marsupiais/genética , Animais , Austrália , Sequência de Bases , Citocromos b/genética , Evolução Molecular , Fósseis , Dados de Sequência Molecular , Filogenia , RNA de Transferência de Ácido Aspártico/genética , RNA de Transferência de Lisina/genética , Análise de Sequência de DNA , América do SulRESUMO
mtDNA haplotypes of representatives of the cosmopolitan peoples of north-central Mexico were studied. Two hundred twenty-three samples from individuals residing in vicinities of two localities in north-central Mexico were analyzed. A combination of strategies was employed to identify the origin of each haplotype, including length variation analysis of the COII and tRNALYS intergenic region, nucleotide sequence analysis of control region hypervariable segment 1, and RFLP analysis of PCR products spanning diagnostic sites. Analysis of these data revealed that the majority of the mtDNA haplotypes were of Native American origin, belonging to one of four primary Native American haplogroups. Others were of European or African origin, and the frequency of African haplotypes was equivalent to that of haplotypes of European derivation. These results provide diagnostic, discrete character, molecular genetic evidence that, together with results of previous studies of classical genetic systems, is informative with regard to both the magnitude of African admixture and the relative maternal contribution of African, European, and Native American peoples to the genetic heritage of Mexico. Phylogenetic analysis revealed that African sequences formed a basal, paraphyletic group.
Assuntos
DNA Mitocondrial/genética , Haplótipos/genética , Filogenia , África/etnologia , Complexo IV da Cadeia de Transporte de Elétrons/genética , Europa (Continente)/etnologia , Feminino , Frequência do Gene/genética , Marcadores Genéticos/genética , Variação Genética/genética , Humanos , Indígenas Norte-Americanos/genética , México , Polimorfismo de Fragmento de Restrição , RNA de Transferência de Lisina/genética , Deleção de Sequência/genéticaRESUMO
Although the deletion of one of the 9-bp repeats in region V of mitochondrial DNA is very common in Asians, Asian-derived populations and Africans, the triplication of the 9-bp segment was described only a few times, mostly on individuals from Asian origin. Here, we report for the first time the presence of the 9-bp triplication in Europeans. The triplication was initially found in one Brazilian individual. Sequencing of the hypervariable segments I (HVSI) and II (HVS2) of the control region and RFLP analysis of the coding region classified the mtDNA as belonging to the European haplogroup H. Since white Brazilians are predominantly of Portuguese descent, we screened 96 unrelated Northern Portuguese for the 9-bp triplication and found its presence in two of them (2.1%). One of these had an mtDNA haplotype identical to that of the Brazilian individual, while the other differed in a single base change in HVS2. The fact that the 9-bp triplication has reached polymorphic frequencies in Northern Portugal and that it has apparently differentiated into at least two lineages defined by the mutuation in HVS2 suggests that it probably occurred a long time ago.