These PRBKO mice do not express the B isoform of the progesterone receptor and 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 PRBKO mice express only the A isoform of the progesterone receptor. An introduced amino acid substitution in the isoform B translational start site (Met-> Leu) prevents expression of isoform B. Homozygous males are viable and fertile. Homozygous females exhibit lactational defects resulting in growth retardation in pups. Mammary gland development and morphogenesis during pregnancy in homozygous females is defective (reduced duct branching & development of alveolar lobules). No gene product (protein) isoform B is detected by Western blot analysis of uterine extracts from estrogen treated homozygous female mice. Expression levels of isoform A is not altered.
A targeting vector designed by Dr. Orla M. Conneely (Baylor College of Medicine) containing a loxP site flanked NEO cassette was used to insert a nucleotide substitution in the isoform B start codon in exon 1. 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 tested for germline transmission. The mice were crossed to C57BL/6. 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 2, 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 the translation of isoform B, the start codon of isoform B was mutated to encode leucine (ATG to CTG). A single loxP site remained in an intron after a floxed selection cassette was excised via cre mediated recombination. While isoform B was undetected by Western blot analysis of homozygous mutant uterine extracts, the presence of isoform A was confirmed.|
When maintaining a live colony, these mice can be bred as homozygotes. Homozygotes are viable and fertile, however, homozygous females have lactational defects, that results in pup growth retardation.
When using the B6;129S7-Pgrtm2Omc/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #022465 in your Materials and Methods section.