These PRAKO mice do not express the A isoform of the progesterone receptor. Homozygous females, while viable, are infertile. This mutant mouse strain may be useful in studies of ovulation, pregnancy, alveolar development in the breast, sexual behavior, and mammary gland tumorigenesis.
Orla M. Conneely, Baylor College of Medicine
The progesterone receptor is a nuclear steroid receptor, ligand activated transcription factor which regulates gene expression following progesterone hormone binding. The progesterone receptor gene has two distinct promoters and translation start sites in the first exon which produce two isoforms, A and B. These PRAKO mice express only the B isoform of the progesterone receptor. An introduced amino acid substitution in the isoform A translational start site at codon 166 (Met-> Ala) prevents expression of isoform A.
Homozygous males are viable and fertile. Homozygous females are viable but infertile, exhibiting severely reduced or absence of ovulation, uterine hyperplasia and inflammation, severely limited mammary gland development, and an inability to exhibit sexual behavior.
No gene product (protein) isoform A is detected by Western blot analysis of uterine extracts from homozygous female mice. Expression levels of isoform B is similar to that seen in wildtype mice.
A targeting vector designed by Dr. Orla M. Conneely (Baylor College of Medicine) containing a floxed NEO selection cassette was used to introduce an amino acid substitution in the isoform A translational start site at codon 166 to encode alanine (Met-> Ala). The construct was electroporated into 129S7/SvEvBrd-Hprtb-m2 derived AB2.2 embryonic stem (ES) cells, which were transiently transfected with a Cre recombinase vector to remove the selection cassette. ES cells that had successfully undergone Cre-mediated recombination and no longer retained the cassette were injected into blastocysts. The resulting chimeric animals were crossed to C57BL/6 mice. Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6J (Stock No. 000664) at least once to establish the colony.
|Allele Name||targeted mutation 1, Orla M Conneely|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Pgr, progesterone receptor|
|Strain of Origin||129S7/SvEvBrd-Hprtb-m2|
|Molecular Note||To eliminate translation of isoform A, without abrogating the translation of isoform B, the translational start site at codon 166, which is specific to isoform A, was modified to encode alanine. For selection, a silent mutation was introduced resulting in the generation of a novel NheI restriction site and a floxed neomycin selection cassette was inserted into intron 2. Recombinant ES cells were transfected with plasmids expressing cre recombinase, resulting in the excision of the neomycin cassette. Immunoblot analysis of uterine extracts from estrogen treated homozygous mutant mice showed an absence of isoform A. Isoform B protein levels were unaffected.|
When maintaining a live colony, these mice can be bred as heterozygotes. Homozygous females are infertile.
When using the B6;129S7-Pgrtm1Omc/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #022464 in your Materials and Methods section.