Search

Recently, we described the identification of a novel protein, nuclear receptor-associated protein 80 (RAP80), which is highly expressed in spermatocytes and appears to have a role in regulating gene expression. To identify proteins interacting with this protein, we performed yeast two-hybrid screening using full-length RAP80 as bait. This screen identified one in-frame clone encoding a novel testis-specific protein (Tsp), referred to as Tsp57. Tsp57 encodes a basic protein with a mass of 56.8 kDa. The amino acid sequence of Tsp57 is highly conserved (87%) between mouse and human. The mouse and human Tsp57 genes map to chromosomes 9A1 and 11q21, respectively. Northern blot analysis showed that the expression of Tsp57 mRNA was highly restricted to the testis and temporally regulated during testicular development. Tsp57 mRNA was greatly induced between Day 21 and Day 25 of postnatal testicular development. In situ hybridization analysis demonstrated that the hybridization signal for Tsp57 mRNA was strongest in sections of seminiferous tubules at stages VI-VIII of spermatogenesis, consistent with the conclusion that Tsp57 is most highly expressed in round spermatids. Study of Tsp57 expression in several purified subpopulations of spermatogenic cells confirmed maximum levels of expression in round spermatids. Consistently, Tsp57 expression was absent in testes from vitamin A-deficient mice, which do not have any round spermatids, and was reduced in RARalpha null mice, which have lowered numbers of round spermatids in their testes. These results indicate the possibility that Tsp57 protein plays a role in the postmeiotic phase of germ cell differentiation. Tsp57 contains two putative nuclear localization signals: NLS1 and NLS2. Examination of the cellular localization showed that the green fluorescent protein-Tsp57 fusion protein localized to both cytoplasm and nucleus. After deletion of NLS1 but not NLS2, Tsp57 localized solely to the cytoplasm, indicating a role for NLS1 in the nuclear localization of Tsp57. The localization suggests a nuclear function for Tsp57. Pull-down analysis demonstrated that Tsp57 and RAP80 form a complex in intact cells.

Copy number variation (CNV) is one of the most profound forms of somatic DNA changes that underlie most human cancers. However, the degree of complexity within and between DNA and mRNA variations in cancer cohorts has yet to be fully characterized. Here we characterized the connectivity of CNV/CNV and its contribution to transcriptome in human cancer cell lines. Strikingly, we found there is a significant nonrandom correlation of many unlinked DNA loci and also a significant association between CNV and mRNA expression in cis and in trans (called eCNV). Both distributions of DNA/DNA and DNA/mRNA associations exhibit a scale-free structure showing that, for DNA/DNA, a few loci correlate to many other loci, whereas most loci correlate to only a few loci; and for DNA/mRNA, certain chromosomal loci associate with many mRNAs and that many mRNAs are controlled by more than one locus. This suggests that a small number of DNA loci act as hubs in a hierarchical structure that is highly nonrandom in nature, and genes linking to these hot spots tend to be involved in similar biological functions. Derivation of highly connected structures suggests a process of undirected copy number changes followed by selection of those advantageous to tumor cells during tumorigenesis. Given that the cohort includes many tissue types, our observations may identify a common and important underlying structure present in human tumors.

Background Identification and characterization of the prostate stem cell is important for understanding normal prostate development and carcinogenesis. The flow cytometry-based side population (SP) technique has been developed to isolate putative adult stem cells in several human tissue types including the prostate. This phenotype is mainly mediated by the ATP-binding cassette membrane transporter ABCG2. Methods Immunolocalization of ABCG2 was performed on normal prostate tissue obtained from radical prostatectomies. Normal human prostate SP cells and ABCG2+ cells were isolated and gene expression was determined with DNA array analysis and RT-PCR. Endothelial cells were removed by pre-sorting with CD31. Results ABCG2 positive cells were localized to the prostate basal epithelium and endothelium. ABCG2+ cells in the basal epithelium constituted less than 1% of the total basal cell population. SP cells constituted 0.5–3% of the total epithelial fraction. The SP transcriptome was essentially the same as ABCG2+ and both populations expressed genes indicative of a stem cell phenotype, however, the cells also expressed many genes in common with endothelial cells. Conclusion These results provide gene expression profiles for the prostate SP and ABCG2+ cells that will be critical for studying normal development and carcinogenesis, in particular as related to the cancer stem cell concept.

BACKGROUND CD10 is a ∼100 kDa transmembrane metallo-endopeptidase. CD10 is strongly expressed by normal prostate epithelium. While only 30% of primary prostate tumors express CD10, it is strongly expressed by most lymph node metastases. The function of CD10 and the interaction between CD10 and other cellular proteins in prostate cancer (CaP) is not well defined. Cellular context may ultimately determine its biologic function in CaP. In this study, we compared CD10 mRNA and protein expression between benign and malignant prostate cells and employed proteomic analysis to identify proteins that interact with CD10 in C4-2 prostate cancer cells. METHODS CD10 mRNA and protein expression was compared using RT-PCR and Western blotting. CD10-protein complexes were isolated by immunoprecipitation using anti-CD10 monoclonal antibodies. Eluted fractions were combined, trypsinized, and the resulting peptides analyzed by µLC-ESI-MS/MS. The parent proteins were identified by searching MS/MS spectra against a human protein database using SEQUEST. RESULTS There were no differences in CD10 mRNA length or CD10 protein molecular weight between normal tissue and CaP. We identified 75 proteins unique to or heavily enriched in the CD10 immunoprecipitates by proteomic analysis. The 27 kDa heat shock protein (HSP27) and HSP70 were identified in three separate precipitations. Protein identification by proteomics was confirmed by Western blotting. Protein complexes immunopurified from C4-2 protein extracts using anti-HSP27 and anti-HSP70 antibodies were found to contain CD10. CONCLUSIONS The function of CD10 in prostate cancer is largely unknown. In the C4-2 CaP cell line, CD10 was found to interact with both HSP27 and HSP70. Prostate 67: 714–721, 2007. © 2007 Wiley-Liss, Inc.

Background The gene expression profiles of most human tissues have been studied by determining the transcriptome of whole tissue homogenates. Due to the solid composition of tissues it is difficult to study the transcriptomes of individual cell types that compose a tissue. To overcome the problem of heterogeneity we have developed a method to isolate individual cell types from whole tissue that are a source of RNA suitable for transcriptome profiling. Results Using monoclonal antibodies specific for basal (integrin β4), luminal secretory (dipeptidyl peptidase IV), stromal fibromuscular (integrin α 1), and endothelial (PECAM-1) cells, respectively, we separated the cell types of the prostate with magnetic cell sorting (MACS). Gene expression of MACS-sorted cell populations was assessed with Affymetrix GeneChips. Analysis of the data provided insight into gene expression patterns at the level of individual cell populations in the prostate. Conclusion In this study, we have determined the transcriptome profile of a solid tissue at the level of individual cell types. Our data will be useful for studying prostate development and cancer progression in the context of single cell populations within the organ.