Figure S1.

Inguinal Myf5-Cre-ROSA^mTmGmice characterization. (A) Picture shows the sampling region of the Myf5-Cre-ROSA^mTmG and Ucp1-iCre-ROSA^mTmG mice in the following experiment. (B) The growth of mammary gland invades the interscapular BAT during pregnancy (left) and lactation (right). (C) Distribution of Myf5⁺ basal clone size in scapular region observed as single cell, 24 cells and 5 cells or more (n = at least 200 clones from two different mice were counted at each time point). (D–G) The posterior inguinal fat pad of Myf5-Cre-ROSA^mTmG mice in the virgin and lactation stages were sectioned and immunostained for KRT14 and KRT8. (H) Cell suspension of mammary cells stained for CD24, CD29, and Lin (CD31 and CD45) from Myf5-Cre-ROSA^mTmG mice were gated in P1 and P2 to remove debris and doublets, hematopoietic, and endothelial cells were discarded in Lin⁻. (I) GFP positive cell were gated in GFP compare to FMO control from mTmG mouse. (J) The distribution of Myf5-GFP cell in the posterior inguinal mammary gland cell population (Lin⁻). (K) Myf5-GFP percentage in the posterior mammary gland Krt14⁺ mammary basal myoepithelial population (defined as Lin⁻:CD24⁺:CD29^hi:Krt14⁺) on day 1 of lactation. The data represent means + s.e.m. (L) The gene expression level of Myf5 in different cell types of Myf5-Cre-ROSA^mTmG mice by Q-PCR (n = 4).