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Maternal age effect and severe germ-line bottleneck in the inheritance of human mitochondrial DNA.

ABSTRACT: The manifestation of mitochondrial DNA (mtDNA) diseases depends on the frequency of heteroplasmy (the presence of several alleles in an individual), yet its transmission across generations cannot be readily predicted owing to a lack of data on the size of the mtDNA bottleneck during oogenesis. For deleterious heteroplasmies, a severe bottleneck may abruptly transform a benign (low) frequency in a mother into a disease-causing (high) frequency in her child. Here we present a high-resolution study of heteroplasmy transmission conducted on blood and buccal mtDNA of 39 healthy mother-child pairs of European ancestry (a total of 156 samples, each sequenced at ?20,000× per site). On average, each individual carried one heteroplasmy, and one in eight individuals carried a disease-associated heteroplasmy, with minor allele frequency ?1%. We observed frequent drastic heteroplasmy frequency shifts between generations and estimated the effective size of the germ-line mtDNA bottleneck at only ?30-35 (interquartile range from 9 to 141). Accounting for heteroplasmies, we estimated the mtDNA germ-line mutation rate at 1.3 × 10(-8) (interquartile range from 4.2 × 10(-9) to 4.1 × 10(-8)) mutations per site per year, an order of magnitude higher than for nuclear DNA. Notably, we found a positive association between the number of heteroplasmies in a child and maternal age at fertilization, likely attributable to oocyte aging. This study also took advantage of droplet digital PCR (ddPCR) to validate heteroplasmies and confirm a de novo mutation. Our results can be used to predict the transmission of disease-causing mtDNA variants and illuminate evolutionary dynamics of the mitochondrial genome.

SUBMITTER: Rebolledo-Jaramillo B

PROVIDER: S-EPMC4217420 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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Maternal age effect and severe germ-line bottleneck in the inheritance of human mitochondrial DNA.

Rebolledo-Jaramillo Boris B Su Marcia Shu-Wei MS Stoler Nicholas N McElhoe Jennifer A JA Dickins Benjamin B Blankenberg Daniel D Korneliussen Thorfinn S TS Chiaromonte Francesca F Nielsen Rasmus R Holland Mitchell M MM Paul Ian M IM Nekrutenko Anton A Makova Kateryna D KD

Proceedings of the National Academy of Sciences of the United States of America 20141013 43

The manifestation of mitochondrial DNA (mtDNA) diseases depends on the frequency of heteroplasmy (the presence of several alleles in an individual), yet its transmission across generations cannot be readily predicted owing to a lack of data on the size of the mtDNA bottleneck during oogenesis. For deleterious heteroplasmies, a severe bottleneck may abruptly transform a benign (low) frequency in a mother into a disease-causing (high) frequency in her child. Here we present a high-resolution study ...[more]

PMID: 25313049

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Project description:IntroductionPolycystic Ovarian Syndrome (PCOS) is a globally prevalent condition that leads to infertility in women. While environmental factors contribute to PCOS, maternal genetics also play a significant role. Currently, there is no definitive test for identifying predisposition to PCOS. Hence, our objective is to discover novel maternal genetic risk factors for PCOS by investigating the genomes of patients from Pakistan.MethodsWe utilized Next-Generation Sequencing (NGS) to sequence the complete mitochondrial DNA of three PCOS patients. Subsequently, we employed MitoTIP (Mitochondrial tRNA Informatics Predictor) and PON-mt-tRNA tools to identify variations in the mitochondrial DNA. Our analysis focused on the genes MT-RNR1, MT-RNR2, MT-ATP6, MT-TL2, and MT-CYTB, which displayed common variations in all three genomes. Additionally, we observed individual variations. The D-loop region exhibited the highest frequency of mutations, followed by the non-coding regions of RNR1 and RNR2 genes. Moreover, we detected frameshift mutations in the mitochondrially encoded NADH Dehydrogenase 2 (MT-ND2) and mitochondrially encoded NADH Dehydrogenase 5 (ND5) genes within individual genomes.ResultsOur analysis unveiled six regions with common variations in the mitochondrial DNA of all three PCOS patients. Notably, the MT-RNR1, MT-RNR2, MT-ATP6, MT-TL2, and MT-CYTB genes exhibited these variations. Additionally, we identified individual variations in the mitochondrial DNA. The D-loop region displayed the highest mutation frequency, followed by the non-coding regions of RNR1 and RNR2 genes. Furthermore, frameshift mutations were detected in the MT-ND2 and ND5 genes within individual genomes.ConclusionThrough our study, we have identified variations in mitochondrial DNA that may be associated with the development of PCOS and have the potential to serve as predisposition tests. Our findings highlight the presence of novel mutations in the MT-RNR1, MT-RNR2, MT-ATP6, MT-TL2, and MT-CYTB genes, as well as frameshift mutations in the MT-ND2 and ND5 genes. Pathogenicity analysis indicated that most variants were likely to result in benign cysts. However, the frameshift mutations in the ND2 gene were associated with a high risk of complications and pathogenicity in PCOS. This is the first report identifying these mutations and their association with PCOS, contributing to our understanding of the genetic factors underlying the condition.

Dataset Information

Maternal age effect and severe germ-line bottleneck in the inheritance of human mitochondrial DNA.

Publications

Maternal age effect and severe germ-line bottleneck in the inheritance of human mitochondrial DNA.

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