International Mammalian Genome Society

The 15th International Mouse Genome Conference (2001)


POSTER 18 - INVESTIGATING THE TRANSMISSION OF HETEROPLASMY IN THE C57/NZB mtDNA HETEROPLASMY MOUSE MODEL

Dr Kerry Fowler
Murdoch Childrens Research Institute
Royal Children's Hospital
Flemington Road
Parkville, Victoria 3052
Australia

Co-Authors: 1) Lewis S, 1) White S, 1) Hutchinson W, 2) Mann J, 1) Thorburn D, 1) Dahl H
Institutions: 1) Murdoch Childrens Research Institute  2) Beckman Research Institute of the City of Hope

Transferring cytoplasm from NZB eggs to C57 eggs generated a model of mtDNA heteroplasmy. The two mtDNAs were discernible by a single base pair polymorphism that abolishes a RsaI site in the NZB mtDNA. There was no major tissue variation found in the levels of heteroplasmy in newborn pups. However, as the mice aged the ratio of NZB mtDNA increased in liver, and decreased in blood and spleen. This model has been followed for 10 generations and the mice are healthy and reproductive. Over time, there appears to be a preferential selection for the C57 mtDNA, ie. the nuclear background strain of the mouse model. This selection is more significant in the latter generations. When the NZB mtDNA heteroplasmy level falls below 5%, it is subsequently lost. Peptide nucleic acids (PNAs) have been injected into the cytoplasm of fertilised eggs in an attempt to alter the level of heteroplasmy in the mouse model by inhibition of replication of the targeted mtDNA. PNAs are synthesised short sequences, which have a DNA-like structure but have a protein backbone. They bind more strongly to DNA and RNA than other single stranded primers and are more stable once inside the cell. Three C57 PNAs were made each with a mitochondrial targeting leader peptide. The corresponding NZB mtDNA sequences differ with 0, 1 and 2 nucleotides. The preliminary results of PNA treatment will be discussed.


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