GSE116831
Deletion of Cdkn1b in ACI rats perturbs mammary progenitor cell proliferation and differentiation through non-cell-autonomous mechanisms
Emerging data indicate that breast epithelial stem cells and progenitors, particularly those in the luminal epithelial cell lineage, are the cells-of-origin of breast carcinomas, and factors that influence breast cancer risk may alter the number and/or properties of these cells. We hypothesize that a subset of p27+ cells represent hormone-responsive progenitors that are quiescent due to the high activity of TGFß signaling in these cells. The Estrogen-induced mammary tumor model in ACI inbred rats is physiologically relevant rodent model of breast cancer. In the present study we successfully generated Cdkn1b knockout ACI rats and performed comprehensive phenotypic assessment and RNAseq profiling using FACS sorted basal (CD24+CD29high) and luminal (CD24+CD29low) cell populations to characterize Cdkn1b+/+ and Cdkn1b-/- females in prepubertal and adult cohorts. We found that p27KO rats exhibited mammary differentiation phenotype and reduced numbers of mammary epithelial progenitor pool, Interestingly, p27 ablation has the most pronounced effect on luminal progenitor cell gene expression, and milk protein genes and pStat5 were dramatically upregulated, while PR and FoxA1 were greatly downregulated in Cdkn1b-/- luminal cells. Further characterization of mammary glands of prepubertal Cdkn1b knockout rats by fat pad transplantation illustrated p27 deletion in the mammary cancer susceptible ACI rat strain induced mammary epithelial cell differentiation through cell non-autonomous mechanisms. Overall design: KO strain nomenclature: ACI.Cg.-Cdkn1bem1Musc (DEL-32) and ACI.Cg.-Cdkn1bem4 (DEL-65). Data was generated with an equal contribution of em1 and em4 for both genotypes (+/+ and -/-, littermates selected from HET crosses, unless indicated otherwise. All KO animals for em1 and em4 had cataracts from birth Bulk RNA-Seq: RNA-Seq of both Cdkn1b knockout and wild type ACI rat mammary glands, at various ages, and various FACS sorted cell types. ChIP-seq: ChIP-seq for PR of both Cdkn1b knockout and wild type 9 week old ACI rat mammary glands, with basal/myoepithelial and luminal FACS sorted cell types. Anti-PR antibody (H-190, Santa Cruz, cat# sc-7208). Bulk RNA-Seq: RNA-Seq of ACI and BN rats treated with and without E2, sorted for luminal and basal fractions of the mammary gland.