Esr1-iCre mice have a codon-improved Cre recombinase inserted upstream of the initiation codon site of exon 2 of the estrogen receptor 1 (alpha) gene (Esr1). Homozygotes are viable but infertile. Because the iCre sequence was inserted in the Esr1 translation initiation codon, homozygous knock-in mice are phenotypically the same as the global Esr1-knockout. When crossed with a strain containing loxP site flanked sequence of interest, iCre-mediated recombination results in deletion of the floxed sequences in the iCre expressing tissues. iCre recombinase expression mimics the endogenous Esr1 gene expression pattern. 

ESR1, a nuclear hormone receptor (NHR), binds to steroid hormones in the cytoplasm, causing their translocation into the nucleus and leading to increased transcription of target genes. These Esr1-iCre knock-in/knock-out mice may be useful for studying the function of this ligand-inducible transcription factor in neuronal differentiation, sympathetic nervous system development, hypothalamus, female reproductive organs (endometrium and ovarian stroma cells) and male efferent duct epithelial cells. They may also be useful for studying ER&alpha;-positive breast cancer and steroid hormone-induced malignancies.

When bred to Ai9 reporter mice (Stock No. <a href="https://www.jax.org/strain/007909">007909</a>), iCre-mediated excision of the stop sequence results in the expression of RFP in Esr1-lineage cells in the skin, reproductive organs, pituitary, brain, digestive tract, lung, thoracic organs, mammary bud and adrenal-kidney complex of double mutant offspring.

Esr1-iCre knock-in/knock-out mice express codon optimized Cre recombinase from the endogenous Esr1 locus. Cre recombinase expression mimics endogenous Esr1 gene expression.

Typically mice are recovered in 12-16 weeks. Contact Customer Service to place an order or for more information.

<a target="_blank" href="https://www.jax.org/jax-mice-and-services/customer-support" rel="noreferrer">Contact Customer Service</a> for more information.