Effect of introducing a large amount of embryonic or somatic mitochondria on development and on mitochondrial inheritance in bovines

Abstract

Recent epidemiologic studies have confirmed that pathologies caused by mutations in the mitochondrial DNA (mtDNA) are a major cause of diseases in humans, affecting at least one in 4,000 people. Nonetheless, due to the unique inheritance pattern of these diseases, there is not a method to prevent their transmission to the next generation. Currently, only the nuclear transfer has the potential to be used to prevent it; however, there are many barriers to be overcome before it becomes available clinically. Recently, we developed a new methodology that enables to remove over than 60% of oocyte/zygote mitochondria. This has led to new perspectives concerning about the use of cytoplasmic transfer as a tool to prevent inheritance of mtDNA diseases. If a large amount of mitochondria was introduced into the depleted zygote, the mutant mtDNA would be diluted to a low level, potentially preventing transmission of many pathologies caused by the mtDNA. Hence, this project aims to investigate two methodologies to introduce a large amount of mitochondria into the depleted zygote to increase in embryos and offspring the introduced mtDNA contribution. Thus, we will test the use of two sources of mitochondria from i) the cytoplasmic fraction rich in mitochondria obtained after zygote centrifugation (embryonic mitochondria) and ii) purified mitochondria from somatic cells (somatic mitochondria). It will be analyzed whether there is an effect of mitochondrial source on development to term as well as the heteroplasmy in offspring. In case of we find a decrease of heteroplasmy during development other studies will be carried out to address the reasons of such effect.