B6.129-Cdc25a^tm1Dvb/J

Stock number: 010533
Research areas: Cancer Research, Cell Biology Research

Description

This targeted mutation of the cell division cycle 25 homolog A (Cdc25a) gene displays radiation-induced tumorigenesis and centrosome amplification in mouse embryonic fibroblasts and may be useful in studies of cell cycle regulation and cancer.

Detailed description

Mice that are homozygous for the targeted mutation are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. S123A Cdc25a protein is altered at a key phosphorylation site. When measured in dermal fibroblasts (DF), the mutant protein has a prolonged half-life as compared to wild-type (60 vs. 90 minutes) suggesting that the mutation stabilizes the protein. DF treated with nocodazole contain cells with an increase in centrosome number. When nocodazole is combined with radiation, aneuploid cells with nearly 4N DNA content are observed. In addition, eighteen months after treatment with ionizing radiation, mice develop tumors at much higher percentage than wild-type (80% vs. 30%). This mutant mouse strain may be useful in studies of cell cycle regulation, centrosome amplification in dermal fibroblasts and radiation-induced tumorigenesis.

In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. It should be noted that the phenotype could vary from that originally described. We will modify the strain description if necessary as published results become available.

Development

The targeting vector was designed to change a key phosphorylation site of the murine Cdc25a cDNA sequence from a serine to alanine at amino acid position 123 (S123A) in exon 5. A loxP-flanked neomycin cassette was also inserted upstream of exon 5. The construct was electroporated into 129-derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts. The resulting chimeric animals were crossed to C57BL/6 mice carrying Cre recombinase under the control of a beta actin promoter to remove the neo cassette leaving behind a single loxP site. Mice were crossed to C57BL/6 for four generations. Upon arrival, mice were bred to C57BL/6J for at least 1 generation to establish the colony.

Allele

Symbol: Cdc25a^tm1Dvb
Name: targeted mutation 1, Dmitry V Bulavin
MGI accession ID: MGI:3831687
Generation method: Targeted
Attributes: Not Specified
Marker symbol: Cdc25a
Marker name: cell division cycle 25A
Chromosome: 9
Strain of origin: 129X1/SvJ
Molecular note: A serine 123 to alanine (S123A) substitution was performed by mutating the TCT codon in exon 5 to GCT. A loxP-flanked neomycin cassette was also included upstream of exon 5 for targeting purposes. Mice generated by correctly targeted ES cells were crossed with cre-transgenic mice to remove the neo cassette leaving behind a single loxP site. Sequence analysis of cDNAs from homozygote embryonic fibroblasts demonstrated the mutated allele was expressed. Immunoblot analysis indicated no differences in basal expression between mutant and wild-type proteins. The mutant protein was found to have a 50% longer half-life than wild-type protein in embryonic fibroblasts.