Body temperature and activity in wild-type (+/+) and PPARβ-null (−/−) mice. Daytime (10 a.m. to 5 p.m.) and nighttime (10 p.m. to 5 a.m.) measurements were made continuously for 14-week-old mice. The body temperature during a 24-hour fast is reported both as the mean of hours 15 to 24 and the minimum during the fast. Values are means ± standard errors of the means (n = 5/group).

Altered myelination of corpus callosum in PPARβ-null mice. Sagittal sections (10 μm) were cut and stained with LFB as described in Materials and Methods. Magnification, ×170. Arrows, regions of altered myelination. (A) Twelve-week-old females; (B) 36-week-old females; (C) 12-week-old males; (D) 36-week-old males.

Northern analysis of skin mRNAs in wild-type (+/+) and PPARβ-null (−/−) mice 8 h after TPA. Ten micrograms of total RNA was analyzed from representative skin from two mice. mRNAs associated with epidermal differentiation and cell proliferation were measured. Con, control.

TPA-induced inflammation in skin of representative wild-type (+/+) and PPARβ-null (−/−) mice fed a sulindac diet, 8 h after TPA treatment. Mice were fed 0.32 g of sulindac/kg of diet for 10 days and treated topically with 5 μg of TPA as described in Materials and Methods. Magnification, ×132. Note that there is less inflammation (blue cells) in dermis and subcutaneous tissue in the wild-type section and more infiltration of inflammatory cells in the dermis and subcutaneous tissue in the PPARβ-null section. The epidermis of the PPARβ-null mouse is approximately twice the size of the wild-type mouse epidermis.

Targeted disruption of the mPPARβ gene. (A) Strategy for the mPPARβ knockout. (I) Partial map of a mouse genomic fragment containing the second-to-last and last exons encoding the mPPARβ ligand binding domain. Restriction enzymes: B, BamHI; Xh, XhoI; Xb, XbaI; A, AflII. The wild-type 9.5-kb BamHI fragment detected by probe A, a 0.65-kb XhoI-AflII fragment from the 3′ end of the mPPARβ genomic DNA, is indicated. (II) Targeting vector with a total of 5.3 kb of homologous sequence contained in the XhoI fragment of the genomic clone. The 1.14-kb NEO gene in the same orientation relative to mPPARβ transcription was inserted into the XbaI site indicated. The NEO cassette introduces a new BamHI restriction site used for genotyping by Southern blot analysis. A pMCITK expression cassette (herpes simplex virus thymidine kinase [HSV-TK]) was added at the 3′ end of the construct for negative selection. DX, disrupted XhoI site. (III) The expected homologous recombination event of mPPARβ. When one allele of the mPPARβ gene was replaced with the targeting vector sequences by homologous recombination, a 6.4-kb restriction fragment appeared when the gene was analyzed with probe A. (B) Genomic Southern blots of ES cell DNA (top) and Southern blot of tail DNA from wild-type (+/+), heterozygous (+/−), and homozygous mutant (−/−) mice (bottom). (C) Northern analysis of PPARβ mRNA in selected tissues from wild-type (+/+) and PPARβ-null (−/−) mice. (D) Western blot analysis of skin and liver from wild-type (+/+) and PPARβ-null (−/−) mice. Samples from skin of TPA-treated mice were also analyzed. +, positive control. Con, control.

Effect of 24-h fasting on gonadal adipose mRNA of PPARγ and CD36/FAT in wild-type (+/+) and PPARβ-null (−/−) mice. Male and female +/+ and −/− mice (8 weeks of age) were used. For expression of CD36 and PPARγ mRNA 5 μg of total RNA was subjected to Northern analysis. Values for the respective hybridization signals normalized to β-actin are means ± standard deviations. ∗, significantly different from wild-type control (P < 0.05). Con, control.

Northern analysis of selected mRNAs from corpora callosa from wild-type (+/+) and PPARβ-null (−/−) mice. The corpus callosum was dissected, RNA was isolated, and 5 μg of total RNA was subjected to Northern analysis. Shown are MBP, PLP, and brain ACS-2. Values for the respective hybridization signals normalized to β-actin are means ± standard deviations.

Analysis of TPA-induced hyperplasia in skin of wild-type (+/+) and PPARβ-null (−/−) mice 48 h posttreatment. (A) Histological examination of representative skin topically treated with 5 μg of TPA 48 h posttreatment. Note the enhanced hyperplasia of the epidermis in the −/− skin compared to similarly treated +/+ skin. Magnification, ×267. (B) Northern analysis of skin RNA 48 h after TPA. Total RNA from skin was isolated and analyzed for mRNAs of genes involved in cell proliferation as described in Materials and Methods. mRNAs for the indicated proteins were measured. Values for the respective hybridization signals normalized to β-actin are means ± standard deviations. ∗, significantly different from wild-type control (P < 0.05). Con, control.