Inverse PPARß/δ agonists suppress oncogenic signaling to the ANGPTL4 gene and inhibit cancer cell invasion.

Besides its established functions in intermediary metabolism and developmental processes, the nuclear receptor peroxisome proliferator-activated receptor ß/δ (PPARß/δ) has a less defined role in tumorigenesis. In the present study, we have identified a function for PPARß/δ in cancer cell invasion. We show that two structurally divergent inhibitory ligands for PPARß/δ, the inverse agonists ST247 and DG172, strongly inhibit the serum- and transforming growth factor ß (TGFß)-induced invasion of MDA-MB-231 human breast cancer cells into a three-dimensional matrigel matrix. To elucidate the molecular basis of this finding, we performed chromatin immunoprecipitation sequencing (ChIP-Seq) and microarray analyses, which identified the gene encoding angiopoietin-like 4 (ANGPTL4) as the major transcriptional PPARß/δ target in MDA-MB-231 cells, previously implicated in TGFß-mediated tumor progression and metastatic dissemination. We show that the induction of ANGPTL4 by TGFß and other oncogenic signals is strongly repressed by ST247 and DG172 in a PPARß/δ-dependent fashion, resulting in the inhibition of ANGPTL4 secretion. This effect is attributable to these ligands' ability to induce a dominant transcriptional repressor complex at the site of transcription initiation that blocks preinitiation complex formation through an histone deacetylase-independent, non-canonical mechanism. Repression of ANGPTL4 transcription by inverse PPARß/δ agonists is functionally linked to the inhibition of cancer cell invasion into a three-dimensional matrix, as (i) invasion of MDA-MB-231 cells is critically dependent on ANGPTL4 expression, (ii) recombinant ANGPTL4 stimulates invasion, and (iii) reverses the inhibitory effect of ST247 and DG172. These findings indicate that a PPARß/δ-ANGPTL4 pathway is involved in the regulation of tumor cell invasion and that its pharmacological manipulation by inverse PPARß/δ agonists is feasible.

Characterization of the porcine AMPK alpha 2 catalytic subunitgene (PRKAA2): genomic structure, polymorphism detection and association study.

AMP-activated protein kinase (AMPK), known as a key regulator of cellular energy homeostasis, plays an important role in regulation of glucose and lipid metabolism, and protein synthesis in mammals. The characterization of porcine PRKAA2 encoding the alpha 2 catalytic subunit of AMPK is reported in this study. PRKAA2 was assigned to porcine chromosome 6q by analysis of radiation hybrids (IMpRH panel), and its genomic structure was determined by BAC sequencing. PRKAA2 spans more than 62 kb and consists of nine exons and eight introns. A total of 25 polymorphisms were identified by re-sequencing approximately 7 kb, including all the exons, exon-intron boundaries and 5' and 3' gene flanking regions using twelve founder animals of a Mangalitsa x Piétrain intercross. Neither of two single nucleotide polymorphisms (SNPs) found in the coding region caused an amino acid substitution. Two SNPs (NM_214266.1: c.236+142A>G and NM_214266.1: c.630C>T) in PRKAA2 were genotyped in the Mangalitsa x Piétrain F(2) cross (n = 589) and two commercial populations [Piétrain (n = 1173) and German Landrace (n = 536)] and evaluated for association with traits of interest (muscle development and fat deposition). Single SNP and haplotype analyses revealed weak associations between the PRKAA2 genotypes and loin muscle area in the investigated populations.

Interspecies comparison of gene structure and computational analysis of gene regulation of 17beta-hydroxysteroid dehydrogenase type 1.

17Beta-hydroxysteroid dehydrogenase type 1 (HSD17B1) is a key enzyme of 17beta-estradiol biosynthesis, and in rodents is additionally involved in testosterone biosynthesis. The human HSD17B1 gene, located on chromosome 17q12-21, is duplicated in tandem, with the 3'-copy being the functional gene. Here we show by sequencing the gene from a diverse set of related species that this duplication is of very recent evolutionary origin, having occurred in the common ancestor of Hominoidae (apes and humans) while being absent in the closely related Old World monkeys (Macaca) and the outgroup species Tupaia belangeri and Mus musculus. By computational analysis of the conserved regulatory elements in the 5'-untranslated (5'-UTR) and putative promoter region of the HSD17B1 gene and, where present, pseudogene, across our broad sample of species we can show significant differences that might point to the origin of the divergent substrate specificity of human and rodent HSD17B1 and highlight potential functionally relevant differences in regulatory patterns in different evolutionary lineages.

DNA sequence and comparative analysis of chimpanzee chromosome 22.

Human-chimpanzee comparative genome research is essential for narrowing down genetic changes involved in the acquisition of unique human features, such as highly developed cognitive functions, bipedalism or the use of complex language. Here, we report the high-quality DNA sequence of 33.3 megabases of chimpanzee chromosome 22. By comparing the whole sequence with the human counterpart, chromosome 21, we found that 1.44% of the chromosome consists of single-base substitutions in addition to nearly 68,000 insertions or deletions. These differences are sufficient to generate changes in most of the proteins. Indeed, 83% of the 231 coding sequences, including functionally important genes, show differences at the amino acid sequence level. Furthermore, we demonstrate different expansion of particular subfamilies of retrotransposons between the lineages, suggesting different impacts of retrotranspositions on human and chimpanzee evolution. The genomic changes after speciation and their biological consequences seem more complex than originally hypothesized.

The DNA sequence of human chromosome 21.

Chromosome 21 is the smallest human autosome. An extra copy of chromosome 21 causes Down syndrome, the most frequent genetic cause of significant mental retardation, which affects up to 1 in 700 live births. Several anonymous loci for monogenic disorders and predispositions for common complex disorders have also been mapped to this chromosome, and loss of heterozygosity has been observed in regions associated with solid tumours. Here we report the sequence and gene catalogue of the long arm of chromosome 21. We have sequenced 33,546,361 base pairs (bp) of DNA with very high accuracy, the largest contig being 25,491,867 bp. Only three small clone gaps and seven sequencing gaps remain, comprising about 100 kilobases. Thus, we achieved 99.7% coverage of 21q. We also sequenced 281,116 bp from the short arm. The structural features identified include duplications that are probably involved in chromosomal abnormalities and repeat structures in the telomeric and pericentromeric regions. Analysis of the chromosome revealed 127 known genes, 98 predicted genes and 59 pseudogenes.