Group A streptococcal surface GAPDH, SDH, recognizes uPAR/CD87 as its receptor on the human pharyngeal cell and mediates bacterial adherence to host cells.

Streptococcal surface dehydrogenase (SDH) is a multifunctional, anchorless protein present on the surface of group A Streptococcus (GAS). It plays a regulatory role in GAS-mediated intracellular signaling events in human pharyngeal cells. Using ligand-binding assays, we have identified an approximately 55 kDa protein as an SDH-specific receptor protein on the surface of Detroit human pharyngeal cells. LC-MS/MS analyses identified this SDH-binding pharyngeal cell-surface-exposed membrane-bound protein as uPAR (urokinase plasminogen activator receptor)/CD87. Ligand-binding assays also revealed that only the N-terminal domain (D1) of uPAR bound to SDH. uPAR-D1 more specifically bound to the C-terminal alpha-helix and two immediate flanking regions of the S-loop of the SDH molecule. Site-directed mutagenesis in GAS resulting in SDH with altered C-terminal ends, and the removal of uPAR from pharyngeal cells by phosphatidylinositol-phopsholipase C treatment decreased GAS ability to adhere to pharyngeal cells. When compared to uninfected Detroit pharyngeal cells, GAS-infected pharyngeal cells showed a transient but a significant increase in the expression of uPAR-specific mRNA, and a prolonged recycling process of uPAR on the cell surface. Together, these results indicate that the specific streptococcal surface protein-pharyngeal cell receptor interaction mediated by SDH and uPAR is modulated during GAS infection of human pharyngeal cells. This interaction significantly contributes to bacterial adherence and thus may play a significant role in GAS pathogenesis by regulating intracellular signaling events in pharyngeal cells.

Heritability and genomics of gene expression in peripheral blood.

We assessed gene expression profiles in 2,752 twins, using a classic twin design to quantify expression heritability and quantitative trait loci (eQTLs) in peripheral blood. The most highly heritable genes (∼777) were grouped into distinct expression clusters, enriched in gene-poor regions, associated with specific gene function or ontology classes, and strongly associated with disease designation. The design enabled a comparison of twin-based heritability to estimates based on dizygotic identity-by-descent sharing and distant genetic relatedness. Consideration of sampling variation suggests that previous heritability estimates have been upwardly biased. Genotyping of 2,494 twins enabled powerful identification of eQTLs, which we further examined in a replication set of 1,895 unrelated subjects. A large number of non-redundant local eQTLs (6,756) met replication criteria, whereas a relatively small number of distant eQTLs (165) met quality control and replication standards. Our results provide a new resource toward understanding the genetic control of transcription.

Retinoic acid regulation of eye and testis-specific transcripts within a complex locus.

We previously used a yeast-based enhancer trap to identify a strong, retinoic acid response element (RARE). We have now characterized testis and eye transcripts that are adjacent to this regulatory element. Bioinformatics analysis of expressed sequence tag (EST) clones and RNase protection, reverse transcription-PCR, and Northern blot assays indicate that these two RNAs are transcribed from the same locus on opposite template strands. This positions the RARE upstream of the testis transcript and downstream of the eye transcript. Additionally, these two RNAs are embedded within the third intron of the 329kbp gene that encodes the Zinc Finger and BTB domain containing 7C protein (Zbtb7C). We present evidence indicating that the testis transcript is expressed primarily in spermatocytes and/or early round spermatids. Furthermore, our analyses of transcript levels in eyes and testes isolated from vitamin A deficient mice or from mice with defects in retinoid storage or signaling indicate that retinoids are required for expression in vivo.