The Ucp1 gene, encodes the uncoupling protein 1, a transmembrane protein found in the mitochondria of brown adipose tissue. In this strain, Cre recombinase expression is under the control of Ucp1 promoter. When crossed with a strain containing a loxP site-flanked sequence of interest, Cre-mediated recombination results in deletion of the flanked sequence in Ucp1 expressing cells.

An IRES-iCre sequence cassette was placed between the coding sequence of exon 6 and 3' UTR of the Ucp1 gene using C57BL/6 embryonic stem cells. Neo cassette flanked by frt sites was inserted at least 300 bp downstream of 3' UTR. This strain was maintained on a C57BL/6 genetic background.

(B and C) In the virgin stage of the Ucp1-Cre-ROSAmTmG mice, the interscapular BAT was stained for mammary markers KRT14 and KRT8. (DeG) During lactation, Ucp1-GFP cells contain mammary basal myoepithelial markers KRT14 and KRT5 in the dorsal region of the anterior mammary gland (D and E) and the posterior mammary gland (F and G). (source: Li L et al.,2017)