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Identification of genes expressed in a mesenchymal subset regulating prostate organogenesis using tissue and single cell transcriptomics

ABSTRACT: Prostate organogenesis involves epithelial growth in response to inductive signalling from specialised subsets of mesenchyme. To identify regulators and morphogens active in mesenchyme, we performed transcriptomic analysis using Tag-seq, RNA-seq, and single cell RNA-seq and defined new mesenchymal subsets and markers. We documented transcript expression using Tag-seq and RNA-seq in female rat Ventral Mesenchymal Pad (VMP) as well as adjacent urethra comprised of smooth muscle and peri-urethral mesenchyme. Transcripts enriched in VMP were identified in Tag-seq data from microdissected tissue, and RNA-seq data derived from cell populations and single cells. We identified 400 transcripts as enriched or specific to the VMP using bio-informatic comparisons of Tag-seq and RNA-seq data. Comparison with single cell RNA-seq identified transcripts yielded 45 transcriptscommon to both approaches. Cell subset analysis showed that VMP and adjacent mesenchyme were composed of distinct cell types and that each tissue was comprised of two subgroups. Markers for these subgroups were highly subset specific. Thirteen transcripts were validated by qPCR to confirm cell specific expression in microdissected tissues, as well as expression in neonatal prostate. Immunohistochemical staining demonstrated that Ebf3 and Meis2 showed a restricted expression pattern in VMP condensed mesenchyme. Taken together, we demonstrate that the VMP shows limited cellular heterogeneity and that our high-resolution transcriptomic analysis identified new mesenchymal subset markers associated with prostate organogenesis.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE103011 | GEO | 2017/11/27

SECONDARY ACCESSION(S): PRJNA399753

REPOSITORIES: GEO

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Project description:Prostate organogenesis is regulated by interactions between mesenchymal and epithelial cells, and via androgen signalling though androgen receptors (AR) expressed in mesenchymal cells. However, there is little knowledge of AR target genes and we have used high resolution genomic methods to examine AR function in subsets of mesenchyme during prostate development. Using ChIP-seq, we defined genomic AR binding sites (ARBS) in microdissected mesenchymal tissues of neonatal male and female rats during prostate growth. By comparing female tissue subsets (ventral mesenchymal pad and urethral smooth muscle) with male tissues (ventral prostate and dorsolateral prostate), we were able to identify sexually dimorphic ARBS. Females had a distinct AR binding profile from males with enrichment of ARBS proximal to gene transcriptional start sites as well as binding to non-classical AR binding sequence motifs. Using both tissue RNA-sequencing and single-cell RNA-sequencing of the same mesenchymal subsets, we identified 128 differentially expressed transcripts between males and females. Comparison of these to ChIP-seq ARBS allowed us to define sexually dimorphic AR target genes. Selected candidates were validated as sexually dimorphic at both the mRNA and protein level in both rat and human developing prostate tissues by qPCR and western blot. Response to testosterone stimulation was examined using ex vivo rat tissue organ cultures and qPCR. In single cell RNAseq data we observed subpopulations of mesenchymal cells in males and females as well as subpopulations common to both. The distribution of AR and target genes did not follow the subpopulation distribution, suggesting that AR action is not restricted by subset identity.Our study is the first to apply multiple transcriptomic approaches to prostate mesenchyme, and we have identified unique AR targets. We have identified sexually dimorphic, androgen responsive mesenchymal target genes that may underlie sexually dimorphic development of the prostate. We suggest that the analysis of transcription factor binding and transcriptomes in cell subsets will be informative when applied to tumour cells and stroma – since these show similar cellular heterogeneity and subset specific activity.

Project description:Malformations of the cardiovascular system are the most common type of birth defect in humans, affecting predominantly the formation of valves and septa. During heart valve and septa formation, cells from the atrio-ventricular canal (AVC) and outflow tract (OFT) regions of the heart undergo an epithelial-to-mesenchymal transformation (EMT) and invade the underlying extracellular matrix to give rise to endocardial cushions. Subsequent maturation of newly formed mesenchyme cells leads to thin stress-resistant leaflets. TWIST1 is a basic helix-loop-helix transcription factor expressed in newly formed mesenchyme cells of the AVC and OFT that has been shown to play roles in cell survival, cell proliferation and differentiation. However, the role and downstream targets of TWIST1 during heart valve formation remain unclear. To identify genes important for heart valve development downstream of Twist1 we performed global gene expression profiling of AVC, OFT, atria and ventricles of the embryonic day 10.5 mouse heart by tag-sequencing (Tag-seq). Using this resource we identified a novel set of 1246 genes, including 201 regulators of transcription, enriched in the valve forming regions of the heart. We compared these genes to a Tag-seq library from the Twist1 null developing valves revealing significant gene expression changes. These changes were consistent with a role of TWIST1 in controlling differentiation of mesenchymal cells following their transformation from endothelium in the mouse. To study the role of TWIST1 at the DNA level we performed chromatin immunoprecipitation and identified novel direct targets of TWIST1 in the developing heart valves. Our findings are consistent with a role for TWIST1 in the differentiation of AVC mesenchyme post-EMT in the mouse, and suggest that TWIST1 exerts its function by direct DNA binding to activate valve specific gene expression. Profiled the AVC, OFT, atria and ventricles of the embryonic day 10.5 mouse heart by tag-sequencing (Tag-seq) (no replicates). We also produced a Tag-seq library from Twist1 null developing valves to reveal the gene expression changes associated with loss of this gene.

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Identification of genes expressed in a mesenchymal subset regulating prostate organogenesis using tissue and single cell transcriptomics

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