Use of D11S2179 and D11S1343 markers as informative markers for prenatal diagnosis in Iranian ataxia-telangiectasia patients

Ataxia-telangiectasia is an autosomal recessive disorder affecting 1/40000 to 1/100000 of reported populations. There is 25% possibility for having an affected child when parents are carriers for ATM gene mutation. There is no cure available for this disease and prenatal testing is strongly recommended to prevent this disease. Although preferred method is the direct mutation analysis of ATM gene, but large size of the ATM gene with 63 exons and the large number of possible mutations in patients considerably limit efficiency of mutation analysis as a choice in diagnosis. Indirect method is a better tool when parents are not carriers of founder mutation and pass different mutations to their children. Indirect molecular diagnosis using ATM related molecular markers facilitates prenatal diagnosis of AT children. In this study, four molecular markers: D11S2179, D11S1787, D11S535, D11S1343 are genotypes in 12 unrelated families [19 patients] from different regions of Iran. Those markers are amplified using extracted sequence primers from Gene Bank with their described PCR conditions. The amplified products were separated using denaturing PAGE gels, and the data were analyzed to detect their pattern of inheritance in each family. In all families, segregation of alleles were according to mandelian inheritance and affected chromosomes were distinguishable from unaffected ones. All carriers and affected patients were diagnosed accurately. Thus, this method is effectively usable in prenatal diagnosis of ataxia telangiectasia

Role of mitochondria in ataxia-telangiectasia: investigation of mitochondrial deletions and haplogroups

Ataxia-Telangiectasia [AT] is a rare human neurodegenerative autosomal recessive multisystem disease that is characterized by a wide range of features including, progressive cerebellar ataxia with onset during infancy, occulocutaneous telangiectasia, susceptibility to neoplasia, occulomotor disturbances, chromosomal instability and growth and developmental abnormalities. Mitochondrial DNA [mtDNA] has the only non-coding regions at the displacement loop [D-loop] region that contains two hypervariable segments [HVS-I and HVS-II] with high polymorphism. We investigated mt-DNA deletions and haplogroups in AT patients. In this study, 24 Iranian patients suffering from AT and 100 normal controls were examined. mt-DNA was extracted from whole blood and examined by 6 primers for existence of mitochondrial deletions. We also amplified and sequenced the mtDNA HVS-I by standard sequencing techniques. mtDNA deletions were observed in 54.1% [13/24] of patients [8.9 kb deletion in all samples, 5.0 kb in one and 7.5 kb in two patients], representing mtDNA damage which may be due to oxidative stress in mitochondria. Our results showed that there is no association between mtDNA haplogroups and AT. This data may indicate involvement of mitochondrial damage in the pathogenesis of AT

Lack of association of mitochondria A3243G tRNA leu mutation in Iranian patients with type 2 diabetes

Many kinds of mutations in mitochondrial [mt] DNA have been reported to be related to the development of Diabetes Mellitus [DM], this type of diabetes has also been shown to be influenced by other genetic factors and/or environmental factors. Among them, tRNALeu[UUR] and its adjacent mtDNA NADH dehydrogenase subunit 1[ND1] region within the mt genome are linked to high susceptibility to DM. A point mutation at 3243 base pair [bp] in the mt tRNA Leu[UUR] is commonly referred to as a syndrome of mitochondrial myopathy, Encephalopathy, Lactic acidosis, and Stroke-like episodes [MELAS]. In the current study, we have assessed the frequency of the A3243G in Iranian diabetic type 2 patients. DNA was obtained from peripheral leukocytes of 154 patients with diabetes Mellitus type2 [l50 with type 2 and 4 with gestational diabetes] and 40 control subjects. Insulin concentration from patients' blood was measured using Radioimmunoassay procedure. Patients showed fasting blood sugar [FBS] between 150-230 mg/dl, body mass index [BMI] between 19-32 Kg/m2 and insulin concentration 0.9-2.35 mg/ml. PCR-RFLP, single strand conformation polymorphism [SSCP] and sequencing methods were used to detect the A3243G or other mutations in the mitochondrial tRNALeu [UUR] gene. A3243G mutation was not detected in patients. SSCP results showed a new pattern of PCR product in 6 patients. The C3316T transition mutation in the ND1 mitochondrial gene was confirmed in selected samples [n=6] by sequencing. No differences were observed between the two groups for C3316T and A3243G mutations [P=0.348]. The mt C3316T mutation did not have any effect on the clinical finding of type 2 diabetes carrying this mutation. These data together with clinical characteristics of the patients may suggest that the mt C3316T mutation might be a polymorphism in the Iranian population