Mice with a homozygous gene trap vector insertion in mgcRacGAP die during pre-implantation development.
In a phenotypic screen in mice using a gene trap approach in embryonic stem cells, we have identified a recessive loss-of-function mutation in the mgcRacGAP gene. Maternal protein is present in the oocyte, and mgcRacGAP gene transcription starts at the four-cell stage and persists throughout mouse pre-implantation development. Total mgcRacGAP deficiency results in pre-implantation lethality. Such E3.5 embryos display a dramatic reduction in cell number, but undergo compaction and form a blastocoel. At E3.0-3.5, binucleated blastomeres in which the nuclei are partially interconnected are frequently observed, suggesting that mgcRacGAP is required for normal mitosis and cytokinesis in the pre-implantation embryo. All homozygous mutant blastocysts fail to grow out on fibronectin-coated substrates, but a fraction of them can still induce decidual swelling in vivo. The mgcRacGAP mRNA expression pattern in post-implantation embryos and adult mouse brain suggests a role in neuronal cells. Our results indicate that mgcRacGAP is essential for the earliest stages of mouse embryogenesis, and add evidence that CYK-4-like proteins also play a role in microtubule-dependent steps in the cytokinesis of vertebrate cells. In addition, the severe phenotype of null embryos indicates that mgcRacGAP is functionally non-redundant and cannot be substituted by other GAPs during early cleavage of the mammalian embryo.
Van de Putte
T
T
Department of Cell Growth, Differentiation and Development (VIB-07), Flanders Interuniversity Institute for Biotechnology (VIB) and Laboratory of Molecular Biology (CELGEN), University of Leuven, Herestraat 49, 3000, Leuven, Belgium.
Zwijsen
A
A
Lonnoy
O
O
Rybin
V
V
Cozijnsen
M
M
Francis
A
A
Baekelandt
V
V
Kozak
C A
CA
Zerial
M
M
Huylebroeck
D
D
D000818:Animals; D015152:Blotting, Northern; D001921:Brain / Q000196:embryology / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004622:Embryo, Mammalian / Q000502:physiology*; D005260:Female; D020549:GTP Phosphohydrolase Activators / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000235:genetics* / Q000502:physiology*; D005697:Galactosides / Q000378:metabolism; D005838:Genotype; D006579:Heterozygote; D006720:Homozygote; D017403:In Situ Hybridization; D007211:Indoles / Q000378:metabolism; D008297:Male; D051379:Mice; D008957:Models, Genetic; D009154:Mutation; D010590:Phalloidine / Q000494:pharmacology; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution; D014158:Transcription, Genetic
D018076:DNA, Complementary; D020549:GTP Phosphohydrolase Activators; D020690:GTPase-Activating Proteins; D005697:Galactosides; D007211:Indoles; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C115995:mgcRacGAP; D010590:Phalloidine; C044888:5-bromo-4-chloro-3-indolyl beta-galactoside