Differential expression of the peroxisome proliferator-activated receptor gamma (PPARgamma) and its coactivators steroid receptor coactivator-1 and PPAR-binding protein PBP in the brown fat, urinary bladder, colon, and breast of the mouse

Abstract

Peroxisome proliferator-activated receptors (PPARs) regulate genes involved in lipid metabolism and adipocyte differentiation. Steroid receptor coactivator-1 (SRC-1) and PPAR-binding protein (PBP) interact with PPARgamma and act as coactivators to enhance ligand-dependent transcription. We report here that PPARgamma, SRC-1, and PBP are differentially expressed in the brown fat, transitional epithelium of the urinary bladder, colonic mucosa, and mammary epithelium of the adult mouse. PPARgamma and PBP are expressed in the transitional epithelium of urinary bladder and in brown adipose tissue, but not SRC-1. In the colonic mucosa, PPARgamma expression occurs throughout the villi, whereas the expression of both SRC-1 and PBP is confined mostly to the crypts. The expression of both SRC-1 and PBP is prominent in the breast epithelium of nonpregnant, pregnant, and lactating mice, whereas PPARgamma expression appeared prominent during lactation. During early embryonic development, PPARgamma, SRC-1, and PBP are differentially expressed, with only limited cell types displaying overlapping expression. PPARgamma and PBP expression overlapped in the brown fat and urogenital sinus at stage E15.5 of embryogenesis, whereas SRC-1 expression occurred mostly in neuroepithelium and cartilage between stages E9.5 and E13.5 of embryogenesis.

Figure 1.

Differential expression of PPARγ, PBP, and mSRC-1 mRNAs in bladder, brown fat, and colon by in situ hybridization. A to F: Expression of PPARγ and PBP in bladder. A and B: Expression of PPARγ in adult mouse bladder transitional epithelium at low (×5) and high (×20) power, respectively. C: Expression of PBP in the adult bladder transitional epithelium. D and E: antisense and sense panels, respectively, for PPARγ expression in the urogenital sinus of a stage E15.5 mouse. F: Hematoxylin and eosin-stained adult urinary bladder for histological reference. A to F, arrows: Transitional epithelium; lu, lumen of the bladder. G and H: High PPARγ and PBP expression in the E15.5 brown fat (arrows), respectively. I: Sense control for PPARγ showing background signal levels compared with G. J to O: Expression of PPARγ, PBP, and SRC-1 in the adult colon. J to L: Photographs taken at low power (×5). M to O: Photographs taken at high power (×20). J and M denote PPARγ expression (J, arrows, colonic villi; M, arrows, entire villus), K and N denote PBP expression, and L and O denote SRC-1 expression. The arrows in K, L, N, and O point to the crypts of the villus. In J to O, lu denotes the lumen of the colon.

Figure 2.

Differential expression of PBP and mSRC-1 mRNAs in murine breast and SRC-1 expression during embryogenesis by in situ hybridization. A and B: PBP in normal and pregnant mouse breast, respectively. C: SRC-1 expression in pregnant breast. A to C, arrowheads, mammary gland epithelium. D and F: SRC-1 expression in E9.5 and E13.5 mouse embryos, respectively. ne, neuroepithelium; so, somites; oe, olfactory epithelium; fe, femur head; ca, cartilage primordium of the vertebral column. F, arrowhead, a developing rib. E and G are the corresponding sense controls showing background hybridization levels.