A self-marker-like protein governs hemocyte allorecognition in Halocynthia roretzi

Authors

Masaki Ema, Keio University
Taizo Okada, Keio University
Miki Takahashi, Keio University
Masato Uchiyama, Keio University
Hideo Kubo, Tokyo Metropolitan Institute of Medical Science
Hideaki Moriyama, University of Nebraska-Lincoln
Hitoshi Miyakawa, Utsunomiya University
Midori Matsumoto, Keio UniversityFollow

ORCID IDs

http://orcid.org/0000-0003-4838-6179

Document Type

Article

Date of this Version

12-16-2019

Citation

The Author(s). 2019

Comments

Ema et al. Zoological Letters (2019) 5:34 https://doi.org/10.1186/s40851-019-0149-8

Abstract

Background: Self-incompatibility, fusion/non-fusion reactions, and contact reactions (CRs) have all been identified as allorecognition phenomena in ascidians. CR is a reaction characteristic of the hemocytes of Halocynthia roretzi, whereby they release phenol oxidase (PO) upon contact with non-self hemocytes. Thus, these cells may represent a primitive form of the vertebrate immune system. In the present study, we focused on the CR of H. roretzi hemocytes and sought to identify self-marker proteins that distinguish between self and non-self cells.

Results: We initially generated a CR-inducing monoclonal antibody against the complete hemocyte membraneprotein complement (mAb11B16B10). This antibody was identified based on the differential induction of PO activity in individual organisms. The level of PO activity induced by this antibody in individual ascidians was consistent with the observed CR-induced PO activity. mAb11B16B10 recognized a series of 12 spots corresponding to a 100-kDa protein, with differing isoelectric points (pIs). A comparison of the 2D electrophoresis gels of samples from CRreactive/ non-reactive individuals revealed that some spots in this series in hemocytes were common to the CRnon- inducible individuals, but not to CR-inducible individuals. We cloned the corresponding gene and named it Halocynthia roretzi self-marker-like protein-1 (HrSMLP1). This gene is similar to the glycoprotein DD3–3 found in Dictyostelium, and is conserved in invertebrates.

Conclusion: We generated a CR-inducing monoclonal antibody (mAb11B16B10) that recognized a series of novel membrane proteins (HrSMLP1) in the hemocytes of H. roretzi. The combination of expressed spots of HrSMLP1 distinguishes non-self cells from self cells with respect to CR inducibility. Given that the HrSMLP1 gene is a single gene, it may represent a novel type of self-marker protein with a role in CR.