New Technological innovation Uncovers Hidden Mitochondrial DNA Mutations

An international team of researchers, led by KAUST stem cell biologist Mo Li, has now quantitatively depicted the genetic maps of mtDNA in single human oocytes (immature eggs) and blastoids (stem cell-based synthetic embryos).^[1] This has exposed molecular attributes of uncommon mtDNA mutations that trigger maternally inherited disorders.

Mitochondria, the “powerhouses” of cells, participate in a critical purpose in mobile communication and metabolism. Human mtDNA is a circular genome made up of 37 genes, encoding 13 proteins and a noncoding D-loop area. Heteroplasmic mutations, inherited from egg cells, can trigger congenital conditions, like maternally inherited Leigh syndrome, and are linked with late-onset intricate conditions.

“Next-generation sequencing has been applied to sequence mtDNA and implicated heteroplasmic mutations as major contributors to metabolic disorder. However the comprehension of mtDNA mutations continues to be confined because of to the constraints of traditional sequencing systems,” states lead creator Chongwei Bi.

“Our new iMiGseq strategy is considerable since it permits full sequencing of person mtDNA in solitary cells, making it possible for for impartial, high-throughput foundation-resolution evaluation of comprehensive-duration mtDNA,” states Bi. iMiGseq resolves many key questions in the industry.

Using third-generation nanopore sequencing technologies, the scientists have characterised mtDNA heteroplasmy in one cells and explained the genetic options of mtDNA in solitary oocytes. They have examined mtDNA in induced pluripotent stem cells derived from sufferers with Leigh syndrome or neuropathy, ataxia or retinitis pigmentosa (NARP). This has revealed elaborate styles of pathogenic mtDNA mutations, including solitary nucleotide variants and substantial structural variants. “We ended up in a position to detect rare mutations with frequencies considerably underneath the classic detection threshold of a person %,” says Mo Li.

In another experiment making use of the new know-how, iMiGseq exposed the likely dangers of unanticipated significant boosts in the frequency of off-focus on mutations, known as heteroplasmy, in a mitochondrial genome modifying system known as mitoTALEN – a genome modifying software that cuts a particular sequence in mitochondrial DNA. It is used to reduce a mutation that brings about mitochondrial encephalomyopathy and stroke-like episodes syndrome in individual-derived induced pluripotent stem cells.

“This highlights the strengths of complete-length mtDNA haplotype evaluation for understanding mitochondrial DNA heteroplasmy alter other distant mtDNA genetic variants may well be unintentionally afflicted by the modifying of a genetically linked sickness-related mutation and there is a need for ultrasensitive techniques to assess the security of enhancing procedures,” says Li.

The researchers also applied iMiGseq to examine one human oocytes from wholesome donors and one human blastoids, synthetic embryos produced from stem cells, to detect uncommon mutations undetectable with standard next-era sequencing. These very low-stage heteroplasmic mutations, possibly inherited as a result of the feminine germline, are joined to mitochondrial disorders and cancer.^[2]

The iMiGseq strategy delivers a novel usually means to correctly depict the total haplotypes of particular person mtDNA in single cells, providing an perfect system for detailing the lead to of mitochondrial mutation-related diseases, assessing the protection of many mtDNA editing tactics and unraveling the one-way links in between mtDNA mutations, getting old and the progress of advanced diseases.

References:

1. “Quantitative haplotype-resolved investigation of mitochondrial DNA heteroplasmy in Human solitary oocytes, blastoids, and pluripotent stem cells” by Chongwei Bi, Lin Wang, Yong Admirer, Baolei Yuan, Samhan Alsolami, Yingzi Zhang, Pu-Yao Zhang, Yanyi Huang, Yang Yu, Juan Carlos Izpisua Belmonte and Mo Li, 4 April 2023, Nucleic Acids Analysis.
   DOI: 10.1093/nar/gkad209
2. “Single-cell personal complete-duration mtDNA sequencing by iMiGseq uncovers unanticipated heteroplasmy shifts in mtDNA editing” by Chongwei Bi, Lin Wang, Yong Enthusiast, Baolei Yuan, Gerardo Ramos-Mandujano, Yingzi Zhang, Samhan Alsolami, Xuan Zhou, Jincheng Wang, Yanjiao Shao, Pradeep Reddy, Pu-Yao Zhang, Yanyi Huang, Yang Yu, Juan Carlos Izpisua Belmonte and Mo Li, 31 March 2023, Nucleic Acids Research.
   DOI: 10.1093/nar/gkad208