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Optimized amplification and single-cell analysis identify GnRH-mediated activation of Rap1b in primary rat gonadotropes.

ABSTRACT: Identifying the early gene program induced by GnRH would help understand how GnRH-activated signaling pathways modulate gonadotrope secretory response. We previously analyzed GnRH-induced early genes in LbT2 cells, however these lack GnRH self-potentiation, a physiological attribute of gonadotropes. To minimize cellular heterogeneity, rat primary pituitary cultures were enriched for gonadotropes by 40-60% using a sedimentation gradient. Given the limited number of gonadotropes, RNA was amplified prior to microarray analysis. Thirty-three genes were up-regulated 40 minutes after GnRH stimulation. Real-time PCR confirmed regulation of several transcripts including fosB, c-fos, egr-2 and rap1b, a small GTPase and member of the Ras family. GnRH stimulated rap1b gene expression in gonadotropes, measured by a sensitive single cell assay. Immunocytochemistry revealed increased Rap1 protein in GnRH-stimulated gonadotropes. These data establish rap1b as a novel gene rapidly induced by GnRH and a candidate to modulate gonadotropin secretion in rat gonadotropes.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE31399 | GEO | 2011/08/17

SECONDARY ACCESSION(S): PRJNA145721

REPOSITORIES: GEO

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Project description:The goals of this study is to enrich the population of ovine gonadotropes via adenovirus-mediated targeting and flow cytometry to compare NGS-derived transcriptome profiling (RNA-seq) of a gonadotrope-enriched cell population to the combined transcriptome of all anterior pituitary cells and apply enrichment method to query the transcriptome of sorted ovine pituitary cells in response to treatment with 10 nM estradiol (E2) for six hours. Methods: mRNA profiles of sheep anterior pituitary cells were generated by deep sequencing, in sextuplicates, using Illumina HiSeq. The sequence reads that passed quality filters were analyzed at the transcript level with GSNAP, followed by featureCounts and then followed by edgeR. qRT–PCR validation was performed using SYBR Green assays. Results: About 124 million sequence reads per sample were mapped to the sheep genome (Oar v.3.1) which identified 17,082 transcripts in the pituitaries. RNA-seq data confirmed overrepresentation of genes known to be expressed in pituitary in sorted samples; 11 of genes (5 gonadotrope-specific and 6 non gonadotrope-specific) were validated with qRT–PCR. RNA-seq data had a linear relationship with qRT–PCR. Approximately 7.2% of the transcripts showed differential expression between the sorted (gonadotropes) and unsorted (all anterior pituitary cells) pituitary cells, with a fold change ≥3 and FDR <0.05. Hierarchical clustering of differentially expressed genes uncovered several as yet uncharacterized genes that may contribute to gonadotrope function. 232 genes were detected as upregulated in the sorted GFP-positive cells treated with E2 (gonadotropes) and 31 were downregulated following E2 treatment with a fold change ≥1.5 and FDR <0.1. Conclusions: Our study represents the first detailed analysis of the gonadotrope transcriptome, with 6 biologic replicates, generated by RNA-seq technology. The data analysis workflows reported here should provide a framework for comparative investigations of gonadotrope expression profiles. This method was applied to determine differentially expressed genes in the sorted population of pituitary cells (gonadotropes) in response to 10 nM E2.

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Optimized amplification and single-cell analysis identify GnRH-mediated activation of Rap1b in primary rat gonadotropes.

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