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Mouse zygotes injected with mitochondria develop normally but the exogenous mitochondria are not detectable in the
1Department of Anatomy and Cellular Biology, School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.
Abstract:
A microinjection procedure to introduce "paternal" mitochondria from a source other than spermatozoa into fertilized mouse eggs is described. When a mitochondrial suspension isolated from the testes or liver of Mus molossinus mice was microinjected into fertilized eggs of CD1 mice, the microinjected zygotes survived, developed normally, and offspring were produced. Mus molossinus mitochondrial DNA can be distinguished from CD1 mitochondrial DNA by Southern blot analyses using restriction enzymes such as Eco R1, Xba 1, or Spe 1. Although up to 120 viable mitochondria were injected, no exogenous mitochondrial DNA was detected in fetal samples or in the brain, liver, heart, testis, or ovary of the mature progeny. Under the experimental conditions used, similar results were obtained when mitochondria from the testes of New Zealand black mice or from testes of Syrian hamsters were microinjected into fertilized CD1 mouse eggs. Failure to detect the exogenous mitochondrial DNA under our assay conditions suggests that microinjected mitochondria from testis or liver did not selectively replicate during embryonic development. The "foreign" mitochondria appear to have the same fate during early embryogenesis as the mitochondria of the spermatozoon.
Insights
Introducing non-spermatozoa mitochondria into mouse eggs via microinjection resulted in healthy offspring. Foreign mitochondrial DNA was not detected in progeny, suggesting they do not replicate during development.
Area of Science:
- Mitochondrial biology
- Developmental biology
- Genetics
Background:
- Mitochondria are crucial organelles for cellular energy production.
- Maternal inheritance of mitochondria is typical in mammals.
- The fate of non-spermatozoa paternal mitochondria during early embryogenesis is not well understood.
Purpose of the Study:
- To investigate the viability and fate of microinjected mitochondria from non-spermatozoa sources into fertilized mouse eggs.
- To determine if exogenous mitochondria can replicate and be transmitted to offspring.
Main Methods:
- Microinjection of mitochondrial suspensions from mouse testes/liver and hamster testes into fertilized CD1 mouse eggs.
- Southern blot analysis using restriction enzymes (Eco R1, Xba 1, Spe 1) to detect exogenous mitochondrial DNA.
- Analysis of fetal samples and mature progeny tissues (brain, liver, heart, testis, ovary).
Main Results:
- Microinjected zygotes survived and developed into normal offspring.
- No exogenous mitochondrial DNA was detected in any fetal samples or mature progeny tissues, despite injecting up to 120 mitochondria.
- Similar results were observed when using mitochondria from different species (Mus molossinus, New Zealand black mice, Syrian hamsters).
Conclusions:
- Microinjected mitochondria from non-spermatozoa sources do not appear to selectively replicate during mouse embryonic development.
- These "foreign" mitochondria share a similar fate during early embryogenesis as typical paternal mitochondria from spermatozoa.
- This study provides insights into the potential for mitochondrial manipulation and the strict control of mitochondrial inheritance.