Esr1 Knockin mouse models

Esr1, the mouse ortholog of human ESR1, encodes estrogen receptor alpha, a nuclear receptor with a ligand-independent AF-1 region, a zinc finger DNA binding domain that recognizes palindromic estrogen response elements as a homodimer, and a ligand binding domain whose helix 12 repositioning creates the AF-2 surface for NCOA coactivators, with additional membrane-initiated signaling from a palmitoylated pool. Acquired ligand binding domain mutations Y537S and D538G stabilize the agonist conformation and drive endocrine therapy resistance, whereas ESR1 fusions and amplification act by other routes, so a conditional knockin of Y537S is the right tool for resistance pharmacology and a floxed null answers lineage requirement in mammary epithelium, uterus, bone, hypothalamus and vasculature. Separation-of-function knockins that disable DNA binding or AF-2 distinguish genomic from nongenomic signaling. Null mice are viable but infertile with uterine hypoplasia, so constitutive alleles are usable, though Esr2 mediates distinct ovarian functions rather than compensating. Pair conditional alleles with a tissue-matched Cre.

Targeting Esr1 preserves positional context compared with viral or BAC approaches. That helps when you quantify expression or map chromatin.