RXR-2, a member of the retinoid x receptor family in Schistosoma mansoni.

A cDNA encoding a second full-length member of the Schistosoma mansoni RXR family (SmRXR-2) was identified. The nucleotide sequence of SmRXR-2 translates into a protein of 784 amino acids with a pI of 7.63 and an approximate mass of 78kDa making it the largest reported RXR to date. Phylogenetic tree analysis provides evidence that SmRXR-2 is the most ancient full-length RXR identified. SmRXR-2 exhibits unique sequence features compared with other RXRs. RT-PCR results demonstrate that the SmRXR-2 gene is constitutively expressed and thus must play multiple roles throughout schistosome development in the vertebrate host.

Evaluation of Schistosoma mansoni retinoid X receptor (SmRXR1 and SmRXR2) activity and tissue distribution.

Recently, we reported the identification of cDNA's encoding retinoid X receptor (RXR) homologues in Schistosoma mansoni. RXRs are known to be involved in the regulation of genes important for homeostasis and development. Previous studies indicated that SmRXR1 plays a role in the regulation of the female-specific gene, p14. Herein, we report that SmRXR2 also binds to cis-elements present in the p14 upstream region when evaluated in yeast reporter strains. SmRXR2 shows a pattern of recognition of cis-sequences present in the p14 gene upstream region different than SmRXR1. However, the SmRXR2 C (DNA binding) domain binds promiscuously in electrophoretic mobility shift assays to cis-elements of the p14 upstream region. The SmRXRs differ in their ability to activate transcription. The N-terminal A/B domain of SmRXR1 is necessary and sufficient for autonomous transcription activation function (AF) in yeast. SmRXR2 does not exhibit an equivalent autonomous AF. SmRXR1 and SmRXR2 fail to dimerize when investigated both in the yeast two-hybrid system and in immunoprecipitation experiments. In situ hybridization experiments using paraffin sections of adult worms demonstrate that SmRXR1 and SmRXR2 exhibit both common and unique cell type distribution which indicates that SmRXR1 and SmRXR2 both play a role in regulating gene expression in certain cells, yet each plays a distinct role in modulating the expression of genes in other cell types. Both SmRXR1 and SmRXR2 localize to vitelline cells. These studies provide a solid basis for improving our understanding of RXRs and their importance in female-specific gene regulation.

Atrioventricular valvular angiectasis in Sprague-Dawley rats.

Subendothelial heart valve angiectasis has been reported in cows, dogs, pigs, rats, mice, and in human fetuses and newborns. We observed a high incidence (62 in 208 animals examined) of spontaneous angiectasis on the atrioventricular (AV) valves in 10- to 40-week-old Sprague-Dawley rats. The angiectasis was observed predominately on the septal cusp of the right AV valve and located near the AV ostium in 57 of 62 animals. Of the remaining 5 valvular angiectases, 2 were present on the parietal cusp of the right AV valve and 3 were on the left AV valve. The angiectases were single or multiple, ranging from 40 to 300 microm in diameter and were characterized by light microscopy as blood-filled dilatations lined by endothelium. Spontaneously occurring abnormalities in normal laboratory animals, such as the spontaneous valvular angiectasis reported here, need to be differentiated from drug-related lesions.

Pharmacologic profiling of transcriptional targets deciphers promoter logic.

The blueprint for cellular diversity and response to environmental change is encoded in the cis-acting regulatory sequences of most genes. Deciphering this 'cis-regulatory code' requires multivariate data sets that examine how these regions coordinate transcription in response to diverse environmental stimuli and therapeutic treatments. We describe a transcriptional approach that profiles the activation of multiple transcriptional targets against combinatorial arrays of therapeutic and signal transducing agents. Application of this approach demonstrates how cis-element composition and promoter context combine to influence transcription downstream of mitogen-induced signaling networks. Computational dissection of these transcriptional profiles in activated T cells uncovers a novel regulatory synergy between IGF-1 and CD28 costimulation that modulates NF-kappaB and AP1 pathways through signaling cascades sensitive to cyclosporin A and wortmannin. This approach provides a broader view of the hierarchical signal integration governing gene expression and will facilitate a practical design of combinatorial therapeutic strategies for exploiting critical control points in transcriptional regulation.

Identification of a cDNA encoding a retinoid X receptor homologue from Schistosoma mansoni. Evidence for a role in female-specific gene expression.

Schistosoma mansoni, a multicelluar eukaryotic blood fluke, is a major cause of morbidity worldwide in humans. The study of female parasite growth, development, and gene regulation is important because the eggs produced are responsible for the pathogenesis observed in schistosomiasis. p14, an eggshell precursor gene expressed only in sexually mature females in response to a male stimulus, is a model for female-specific gene regulation. The upstream region of the p14 gene shares sequences present in insect genes known to be regulated in a sex-, temporal-, and tissue-specific manner by members of the steroid receptor superfamily. Herein, we report the identification and characterization of a cDNA that encodes the S. mansoni (Sm) RXR homologue. Sequence analysis predicts and Western blot analysis confirms the synthesis of a 74-kDa protein, the largest member of the RXR family reported to date. We show by electrophoretic mobility shift assay analysis that SmRXR binds to cis-elements of the p14 gene including a direct repeat that follows the "3-4-5" rule of binding elements recognized by members of the steroid receptor superfamily. Furthermore, we demonstrate that SmRXR can act as a transcription activator in the yeast one-hybrid system. Through quantitative reverse transcriptase-polymerase chain reaction, we show that the SmRXR gene is constitutively expressed and thus must play multiple roles throughout the schistosome life cycle.