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Molecular and Cellular Biology, January 2001, p. 644-654, Vol. 21, No. 2
Department of Cell and Molecular
Biology, Northwestern Medical School, Chicago, Illinois 60611
Received 6 October 2000/Accepted 16 October 2000
In vitro studies have implicated nuclear respiratory factor 1 (NRF-1) in the transcriptional expression of nuclear genes required for
mitochondrial respiratory function, as well as for other fundamental cellular activities. We investigated here the in vivo function of NRF-1
in mammals by disrupting the gene in mice. A portion of the NRF-1 gene
that encodes the nuclear localization signal and the DNA-binding and
dimerization domains was replaced through homologous recombination by a
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.2.644-654.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Mitochondrial DNA Instability and Peri-Implantation
Lethality Associated with Targeted Disruption of Nuclear
Respiratory Factor 1 in Mice
-galactosidase-neomycin cassette. In the mutant allele,
-galactosidase expression is under the control of the NRF-1
promoter. Embryos homozygous for NRF-1 disruption die between embryonic
days 3.5 and 6.5.
-Galactosidase staining was observed in growing
oocytes and in 2.5- and 3.5-day-old embryos, demonstrating that the
NRF-1 gene is expressed during oogenesis and during early stages of
embryogenesis. Moreover, the embryonic expression of NRF-1 did not
result from maternal carryover. While most isolated wild-type and
NRF-1+/
blastocysts can develop further in vitro, the
NRF-1
/
blastocysts lack this ability despite their
normal morphology. Interestingly, a fraction of the blastocysts from
heterozygous matings had reduced staining intensity with rhodamine 123 and NRF-1
/
blastocysts had markedly reduced levels of
mitochondrial DNA (mtDNA). The depletion of mtDNA did not coincide
with nuclear DNA fragmentation, indicating that mtDNA loss was not
associated with increased apoptosis. These results are consistent with
a specific requirement for NRF-1 in the maintenance of mtDNA and respiratory chain function during early embryogenesis.
*
Corresponding author. Mailing address: Department of
Cell and Molecular Biology, Northwestern University Medical School, 303 East Chicago Ave., Chicago, IL 60611. Phone: (312) 503-2946. Fax: (312)
503-0798. E-mail: rsc248{at}nwu.edu.
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