Center for Embryonic Cell and Gene Therapy, Oregon Health & Science University, Portland, OR, USA.
Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, OR, USA.
Hum Reprod. 2021 Jan 25;36(2):493-505. doi: 10.1093/humrep/deaa308.
What are the long-term developmental, reproductive and genetic consequences of mitochondrial replacement therapy (MRT) in primates?
Longitudinal investigation of MRT rhesus macaques (Macaca mulatta) generated with donor mtDNA that is exceedingly distant from the original maternal counterpart suggest that their growth, general health and fertility is unremarkable and similar to controls.
Mitochondrial gene mutations contribute to a diverse range of incurable human disorders. MRT via spindle transfer in oocytes was developed and proposed to prevent transmission of pathogenic mtDNA mutations from mothers to children.
STUDY DESIGN, SIZE, DURATION: The study provides longitudinal studies on general health, fertility as well as transmission and segregation of parental mtDNA haplotypes to various tissues and organs in five adult MRT rhesus macaques and their offspring.
PARTICIPANTS/MATERIALS, SETTING, METHODS: MRT was achieved by spindle transfer between metaphase II oocytes from genetically divergent rhesus macaque populations. After fertilization of oocytes with sperm, heteroplasmic zygotes contained an unequal mixture of three parental genomes, i.e. donor (≥97%), maternal (≤3%), and paternal (≤0.1%) mitochondrial (mt)DNA. MRT monkeys were grown to adulthood and their development and general health was regularly monitored. Reproductive fitness of male and female MRT macaques was evaluated by time-mated breeding and production of live offspring. The relative contribution of donor, maternal, and paternal mtDNA was measured by whole mitochondrial genome sequencing in all organs and tissues of MRT animals and their offspring.
Both male and female MRT rhesus macaques containing unequal mixture of three parental genomes, i.e. donor (≥97%), maternal (≤3%), and paternal (≤0.1%) mtDNA reached healthy adulthood, were fertile and most animals stably maintained the initial ratio of parental mtDNA heteroplasmy and donor mtDNA was transmitted from females to offspring. However, in one monkey out of four analyzed, initially negligible maternal mtDNA heteroplasmy levels increased substantially up to 17% in selected internal tissues and organs. In addition, two monkeys showed paternal mtDNA contribution up to 33% in selected internal tissues and organs.
N/A.
LIMITATIONS, REASONS FOR CAUTION: Conclusions in this study were made on a relatively low number of MRT monkeys, and on only one F1 (first generation) female. In addition, monkey MRT involved two wildtype mtDNA haplotypes, but not disease-relevant variants. Clinical trials on children born after MRT will be required to fully determine safety and efficacy of MRT for humans.
Our data show that MRT is compatible with normal postnatal development including overall health and reproductive fitness in nonhuman primates without any detected adverse effects. 'Mismatched' donor mtDNA in MRT animals even from the genetically distant mtDNA haplotypes did not cause secondary mitochondrial dysfunction. However, carry-over maternal or paternal mtDNA contributions increased substantially in selected internal tissues / organs of some MRT animals implying the possibility of mtDNA mutation recurrence.
STUDY FUNDING/COMPETING INTEREST(S): This work has been funded by the grants from the Burroughs Wellcome Fund, the National Institutes of Health (RO1AG062459 and P51 OD011092), National Research Foundation of Korea (2018R1D1A1B07043216) and Oregon Health & Science University institutional funds. The authors declare no competing interests.
线粒体替换疗法（MRT）在灵长类动物中的长期发育、生殖和遗传后果是什么？
对使用与原始母体对应物差异极大的供体 mtDNA 生成的 MRT 恒河猴（Macaca mulatta）进行的纵向研究表明，它们的生长、总体健康和生育能力无明显异常，与对照组相似。
线粒体基因突变导致多种无法治愈的人类疾病。通过卵母细胞中的纺锤体转移开发了 MRT，并提议防止母体致病性 mtDNA 突变传递给孩子。
研究设计、大小、持续时间：该研究提供了关于一般健康、生育能力以及供体 mtDNA 单倍型在五只成年 MRT 恒河猴及其后代的各种组织和器官中的传播和分离的纵向研究。
参与者/材料、设置、方法：通过来自遗传上不同的恒河猴群体的中期 II 期卵母细胞之间的纺锤体转移实现 MRT。卵母细胞与精子受精后，异质合子含有三种亲本基因组的不相等混合物，即供体（≥97%）、母体（≤3%）和父体（≤0.1%）线粒体（mt）DNA。MRT 猴子长到成年，定期监测其发育和总体健康状况。通过时间交配繁殖和生产活后代来评估雄性和雌性 MRT 猕猴的生殖适应性。通过全线粒体基因组测序测量 MRT 动物及其后代所有器官和组织中供体、母体和父体 mtDNA 的相对贡献。
含有三种亲本基因组的不相等混合物的雄性和雌性 MRT 恒河猴，即供体（≥97%）、母体（≤3%）和父体（≤0.1%）mtDNA 均达到健康成年，具有生育能力，大多数动物稳定维持初始亲本 mtDNA 异质性比率，并将供体 mtDNA 从雌性传递给后代。然而，在分析的四只猴子中，有一只猴子最初可忽略不计的母体 mtDNA 异质性水平在选定的内部组织和器官中大幅增加至 17%。此外，两只猴子在选定的内部组织和器官中表现出高达 33%的父体 mtDNA 贡献。
无。
局限性、谨慎的原因：本研究的结论是基于相对较少数量的 MRT 猴子，并且仅基于一只第一代雌性。此外，猴子 MRT 涉及两种野生型 mtDNA 单倍型，但不涉及与疾病相关的变体。需要对 MRT 后出生的儿童进行临床试验，以充分确定 MRT 对人类的安全性和有效性。
我们的数据表明，MRT 与非人类灵长类动物的正常产后发育（包括整体健康和生殖适应性）兼容，没有任何检测到的不良影响。来自遗传上遥远 mtDNA 单倍型的 MRT 动物中的“不匹配”供体 mtDNA 甚至不会引起继发性线粒体功能障碍。然而，在一些 MRT 动物的某些内部组织/器官中，母体或父体 mtDNA 的携带量大幅增加，这意味着 mtDNA 突变再次发生的可能性。
研究资金/利益冲突：这项工作得到了 Burroughs Wellcome 基金、美国国立卫生研究院（RO1AG062459 和 P51 OD011092）、韩国国家研究基金会（2018R1D1A1B07043216）和俄勒冈健康与科学大学机构资金的资助。作者没有利益冲突。
