Project description:Deletions and duplications in mitochondrial DNA (mtDNA) cause mitochondrial disease and accumulate in conditions such as cancer and age-related disorders, but validated high-throughput methodology that can readily detect and discriminate between these two types of events is lacking. Here we establish a computational method, MitoSAlt, for accurate identification, quantification and visualization of mtDNA deletions and duplications from genomic sequencing data. Our method was tested on simulated sequencing reads and human patient samples with single deletions and duplications to verify its accuracy. Application to mouse models of mtDNA maintenance disease demonstrated the ability to detect deletions and duplications even at low levels of heteroplasmy.
Project description:Gene expression and phenotypic consequences of laboratory housing in rats. Disease related-phenotypes and associated gene expressions of sedentary animals (living solely in a standard cage) were compared with animals that had access to twice-weekly one-hour physical activity in a large box (PA) and with those that had access to voluntary running wheel exercise (EX). Keywords: exercise dose reponse, sedentary, twice weekly physical activity, daily exercise
Project description:Mitochondrial DNA (mtDNA) deletions are a common cause of mitochondrial disorders and have been found to accumulate during normal aging. Despite the fact that hundreds of deletions have been characterized at the molecular level, their mechanisms of genesis are unknown. We tested the effect of double-strand breaks of muscle mtDNA by developing a mouse model in which a mitochondrially targeted restriction endonuclease (PstI) was expressed in skeletal muscle of mice. Because mouse mtDNA harbors two PstI sites, transgenic founders developed a mitochondrial myopathy associated with mtDNA depletion. The founders showed a chimeric pattern of transgene expression and their residual level of wild-type mtDNA in muscle was approximately 40% of controls. We were able to identify the formation of large mtDNA deletions in muscle of transgenic mice. A family of mtDNA deletions was identified, and most of these rearrangements involved one of the PstI sites and the 3' end of the D-loop region. The deletions had no or small direct repeats at the breakpoint region. These features are essentially identical to the ones observed in humans with multiple mtDNA deletions in muscle, suggesting that double-strand DNA breaks mediate the formation of large mtDNA deletions.
Project description:Somatic mtDNA mutations and deletions in particular are known to clonally expand within cells, eventually reaching detrimental intracellular concentrations. The possibility that clonal expansion is a slow process taking a lifetime had prompted an idea that founder mutations of mutant clones that cause mitochondrial dysfunction in the aged tissue might have originated early in life. If, conversely, expansion was fast, founder mutations should predominantly originate later in life. This distinction is important: indeed, from which mutations should we protect ourselves - those of early development/childhood or those happening at old age? Recently, high-resolution data describing the distribution of mtDNA deletions have been obtained using a novel, highly efficient method (Taylor et al., ). These data have been interpreted as supporting predominantly early origin of founder mutations. Re-analysis of the data implies that the data actually better fit mostly late origin of founders, although more research is clearly needed to resolve the controversy.
Project description:The genomic architecture of the 10q22q23 region is characterised by two low-copy repeats (LCRs3 and 4), and deletions in this region appear to be rare. We report the clinical and molecular characterisation of eight novel deletions and six duplications within the 10q22.3q23.3 region. Five deletions and three duplications occur between LCRs3 and 4, whereas three deletions and three duplications have unique breakpoints. Most of the individuals with the LCR3-4 deletion had developmental delay, mainly affecting speech. In addition, macrocephaly, mild facial dysmorphisms, cerebellar anomalies, cardiac defects and congenital breast aplasia were observed. For congenital breast aplasia, the NRG3 gene, known to be involved in early mammary gland development in mice, is a putative candidate gene. For cardiac defects, BMPR1A and GRID1 are putative candidate genes because of their association with cardiac structure and function. Duplications between LCRs3 and 4 are associated with variable phenotypic penetrance. Probands had speech and/or motor delays and dysmorphisms including a broad forehead, deep-set eyes, upslanting palpebral fissures, a smooth philtrum and a thin upper lip. In conclusion, duplications between LCRs3 and 4 on 10q22.3q23.2 may lead to a distinct facial appearance and delays in speech and motor development. However, the phenotypic spectrum is broad, and duplications have also been found in healthy family members of a proband. Reciprocal deletions lead to speech and language delay, mild facial dysmorphisms and, in some individuals, to cerebellar, breast developmental and cardiac defects.