Methodology article

Establishment of a new method for precisely determining the functions of individual mitochondrial genes, using Dictyostelium cells

Junji Chida^1,2 , Aiko Amagai¹ , Masashi Tanaka³ and Yasuo Maeda¹

¹Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan

²Division of Enzyme Chemistry, Institute for Enzyme Research, Tokushima University, Tokushima, Tokushima 770-8503, Japan

³Genomics for Longevity and Health, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo 173-0015, Japan

author email corresponding author email

BMC Genetics 2008, 9:25doi:10.1186/1471-2156-9-25

Published:	21 March 2008

Abstract

Background

Disruption of mitochondrial genes may become a powerful tool for elucidating precisely the functions of individual mitochondrial genes. However, it is generally difficult to manipulate genetically mitochondrial genes, because 1) a mitochondrion is surrounded by inner and outer membranes, and 2) there are a large number of mtDNA copies in a single cell. This is the reason why we tried to establish a novel method for disrupting a certain mitochondrial gene (rps4), using Dictyostelium cells.

Results

Here, we have developed a new method for specifically disrupting a mitochondrial gene (rps4 ; ribosomal protein subunit S4), by a combination of homologous recombination and delivery of an appropriate restriction endonuclease (SfoI) into mitochondria. First, mitochondrially targeted SfoI whose expression is under control of the tetracycline (Tet)-regulated gene expression system was introduced into cells heteroplasmic with respect to the rps4 gene. Then, the heteroplasmic cells were produced by homologous recombination by use of the construct in which the unique SfoI site and the 5'-half of the rps4 coding region were deleted not to be digested by SfoI, and therefore their mitochondria have both the wild-type mtDNA and the mutant mtDNA with the disrupted rps4 gene. In response to removal of Tet from growth medium, SfoI was selectively delivered into mitochondria and digested only the wild-type mtDNA but not the mutated rps4. Thus one can gain rps4-null cells with only the mutated mtDNA, under the Tet-minus condition.

Conclusion

The mitochondrial gene-disruption method presented here must be widely useful for precisely determining the functions of individual mitochondrial genes. This is the first report to demonstrate complete and specific mitochondrial gene disruption.