Journal Article

Transcriptomic analysis of sea cucumber (Holothuria leucospilota) coelomocytes revealed the echinoderm cytokine response during immune challenge

Wu, Xiaofen, Jiang, Xiao, Ruan, Yao, Ren, Chunhua, Cheng, Chuhang, Yu, Zonghe, Chen, Ting, Huo, Da

2020

Overview

Background The sea cucumber Holothuria leucospilota belongs to echinoderm, which is evolutionally the most primitive group of deuterostomes. Sea cucumber has a cavity between its digestive tract and the body wall that is filled with fluid and suspended coelomic cells similar to blood cells. The humoral immune response of the sea cucumber is based on the secretion of various immune factors from coelomocytes into the coelomic cavity. The aim of this study is to lay out a foundation for the immune mechanisms in echinoderms and their origins in chordates by using RNA-seq. Results Sea cucumber primary coelomocytes were isolated from healthy H. leucospilota and incubated with lipopolysaccharide (LPS, 10 μg/ml), polyinosinic-polycytidylic acid [Poly (I:C), 10 μg/ml] and heat-inactived Vibrio harveyi (10 7 cell/ml) for 24 h, respectively. After high-throughput mRNA sequencing on an Illumina HiSeq2500, a de novo transcriptome was assembled and the Unigenes were annotated. Thirteen differentially expressed genes (DEGs) were selected randomly from our data and subsequently verified by using RT-qPCR. The results of RT-qPCR were consistent with those of the RNA-seq ( R 2  = 0.61). The top 10 significantly enriched signaling pathways and immune-related pathways of the common and unique DEGs were screened from the transcriptome data. Twenty-one cytokine candidate DEGs were identified, which belong to 4 cytokine families, namely, BCL/CLL, EPRF1, IL-17 and TSP/TPO. Gene expression in response to LPS dose-increased treatment (0, 10, 20 and 50 μg/ml) showed that IL-17 family cytokines were significantly upregulated after 10 μg/ml LPS challenge for 24 h. Conclusion A de novo transcriptome was sequenced and assembled to generate the gene expression profiling across the sea cucumber coelomocytes treated with LPS, Poly (I:C) and V. harveyi . The cytokine genes identified in DEGs could be classified into 4 cytokine families, in which the expression of IL-17 family cytokines was most significantly induced after 10 μg/ml LPS challenge for 24 h. Our findings have laid the foundation not only for the research of molecular mechanisms related to the immune response in echinoderms but also for their origins in chordates, particularly in higher vertebrates.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Analysis / Animal Genetics and Genomics / Animals / Annotations / Bioinformatics / Biomedical and Life Sciences / Blood cells / Body wall / Chordata / Chordata - genetics / Chronic lymphocytic leukemia / Coelomocytes / Comparative and evolutionary genomics / Cytokines / Cytokines - genetics / Differentailly expressed genes / Echinodermata / Gastrointestinal tract / Gene expression / Gene Expression Profiling / Gene Expression Regulation / Gene sequencing / Genes / Genomes / Genomics / High-Throughput Nucleotide Sequencing / Holothuria leucospilota / Immune response / Immune response (humoral) / Immune system / Immunity, Humoral - genetics / Information processing / Interleukin 17 / Life Sciences / Lipopolysaccharides / Metabolism / Metamorphism / Microarrays / Microbial Genetics and Genomics / Mitogens / Molecular modelling / Origins / Plant Genetics and Genomics / Poly I-C / Polyinosinic:polycytidylic acid / Proteomics / Research Article / Ribonucleic acid / RNA / RNA sequencing / RNA, Messenger - genetics / RNA-Seq / Sea cucumber / Sea Cucumbers - cytology / Sea Cucumbers - genetics / Sea Cucumbers - immunology / Transcriptome / Vegetables / Vertebrates / Vibrio / Waterborne diseases