Transcriptome analysis of distinct coelomocyte populations in Strongylocentrotus purpuratus

Abstract

Abstract Coelomocytes are important cellular mediators of immunity in echinoderms. In the purple sea urchin (Strongylocentrotus purpuratus) these cells can readily be divided into phagocytes, vibratile cells, red spherule cells, and colorless spherule cells based on their morphology. While some information has been reported about genes that are expressed in specific types of coelomocytes, a comprehensive analysis of the gene expression pattern in each cell type was not available. Using a density gradient coelomocytes from individual adult urchins were separated into three populations (phagocytes, a mixture of vibratile and colorless spherule cells, and red spherule cells), RNA was isolated, and next generation sequencing was employed to determine the transcriptome of each cell population. All three cell populations showed clear differences in their gene expression patterns, and the differences in transcript levels for selected genes that were found to be uniquely expressed in one cell type were confirmed by qRT-PCR using cDNA obtained from additional sea urchins. This bulk population data was then complemented by single-cell RNAseq to obtain information about suitable population and sub-population markers for subsequent studies of coelomocyte biology.