Mitochondria have essential role in cellular energy metabolism and defects in their function lead to many metabolic diseases. Mitochondrial DNA (mtDNA) mutations have been associated with number diseases such as nonsyndromic and aminoglycoside-induced hearing loss. Mutational screening of entire 12SrRNA and tRNA (ser (UCN)) genes in 107 unrelated Iranian patients with amino glycoside-induced and nonsyndromic bilateral hearing loss by direct sequencing analysis method were performed. Twenty different homoplasmic sequence variants were identified; including fifteen common polymorphisms, two putatively pathogenic variants: m.921T>C and m.1005T>C, one 12SrRNA sequence variant m.739C>T and two nucleotides substitution; m.1245T>C and m.1545T>C. Deafness-associated mutation, m.1555A>G, was not found. In our patients we found the mutation 1005 was associated with R haplogroup. These finding show that m.1555A>G mutation is not important in our population. Nucleotide change, m.739C>T, previously reported with very low frequency. We suggested the variation of two nucleotides 1245 and 1545 that localized at conserved site of 12SrRNA may be new candidate for amino glycoside-induced and nonsyndromic hearing impairment associated mutations. However, aminoglycoside exposure is a risk factor for clinical phenotype appearance of these mutations.

Motor learning might be affected by environmental factors as well as some genetic factors. The aim of the present study is to examine the effect of val66met BDNF polymorphism on motor learning and to examine the possibility of moderating this effect using environmental factors. One hundred students from University of Kashan, Iran participated in the study. After extraction of Genomic DNA, implementation of polymerase chain reaction (PCR), analyzing PCR by 1.5 percent Electrophoresis Gel, and in the end sequencing by ABI PRISM 7000 Sequencing Analyzer, 46 participants were identified without val66met polymorphism while 54 participants were affected by the polymorphism (met-carrier). Twenty-four participants without val66met polymorphism and Twenty-four participants of met-carriers were randomly selected and divided into four groups of twelve. Participants of each group practiced backhand baseball pitch for six sessions and after 48 hours did the first retention test. Subsequently, participants in all four groups continued practicing in three additional sessions with specific design for each group and afterwards did the second retention test. Results demonstrate the fact that participants without the polymorphism exceeded met-carriers in learning of the task. Whereas the weakness of met-carriers did not disappear by additional practice, the practice was useful when associated with self-controlled feedback. The research shows val66met polymorphism may exert an influence over the learning of motor skills. However, the effect may be moderated by changing the condition of practice for people affected by the polymorphism in a way that engages them to cognitive processes.

We present a patient with non-syndromic and sensorineural hearing impairment with a novel mitochondrial DNA transition. A 7-year-old boy showed progressive deafness. He gradually lost his hearing ability and his hearing function did not improve with hearing aids. Laboratory data revealed normal blood lactate and pyruvate levels. Genetic analyses for mitochondrial DNA and GJB2 and GJB6 genes were performed. Mitochondrial genes analysis revealed a novel heteroplasmic nucleotide substitution, m.628C>T, in the phenylalanine transfer RNA gene. This case study reveals m.628C>T transition as a novel mitochondrial nucleotide change which may be important in mitochondrial deafness.

Background: The brain-derived neurotrophic factor (BDNF) is a neurotrophic factor in the brain associated with the growth, synaptic plasticity, learning, and cognitive processes. Objectives: The presence of val66met polymorphism in codon 66 of the BDNF gene disturbs this protein’s secretion. The study investigates the effect of this polymorphism on attention, visuomotor performance, and implicit motor sequence learning. Methods: In the present study, 100 students from the University of Kashan, Iran, with the mean age of 21.60 ± 2.20 years, were enrolled. Following extraction of Genomic DNA, implementation of polymerase chain reaction (PCR), analyzing PCR, and DNA sequencing, 46 students were recognized without val66met polymorphism, while 54 students were affected by the polymorphism. In the beginning, participants of each group performed the Stroop color-word test. The Stroop color-word test was performed on one day, and afterward, the serial reaction time test was performed on another day. Results: The results showed that students with the polymorphism were significantly performed weaker than those without the polymorphism in the Stroop test (P = 0.001), visuomotor performance test (P = 0.001), and implicit motor learning (P = 0.006). However, no significant difference between the groups was observed in the Stroop test score (P = 0.637). Conclusions: In general, the results show the effect of the polymorphism on visuomotor performance, implicit motor sequence learning, and selective attention. Therefore, this polymorphism in some individuals may weaken their ability, probably through disturbance in BDNF expression.

Introduction: Brain-derived neurotrophic factor (BDNF) is one of the most abundant neurotrophic factors in the adult brain associated with synaptic plasticity, learning, memory and cognitive processes reinforcement. The advent of val66met polymorphism in codon 66 of the BDNF gene, disrupted this protein's secretion. The purpose of the study is to investigate of the effect of brain-derived neurotrophic factor single nucleotide polymorphism on memory score and memory quotient. Methods: One hundred native male students from Kashan University, Iran (mean age 21.60 ±2.20) were randomly selected. After extraction of Genomic DNA, the polymerase chain reaction (PCR) was implemented by forwarding primer 5-ACTCTGGAGAGC-GTGAAT-3 and reverse primer 5-ATACTGTCACACACGCTG-3, analyzing PCR by 1.5 percent Electrophoresis Gel. In the end, sequencing by ABI PRISM 7000 Sequencing Analyzer, some participants were identified without val66met polymorphism while the others were affected by the polymorphism (met-carrier). We used Wechsler memory tested assess memory score and memory quotient of participants. Also, we used from SPSS software for data analysis and test the research hypothesis. Results: Results revealed that people without the polymorphism were significantly better than met-carriers in memory score and memory quotient (P<0.001). The study of Wechsler's subscales showed that this superiority was more affected by logical memory subscales and associative learning. Conclusion: In general, the results represent the effect of val66met polymorphism on memory and memory quotient, so that the existence of this polymorphism in some people may weaken their ability in compression with people without polymorphism, due to disruption of BDNF secretion.