Rhodopsin and melanopsin coexist in mammalian sperm cells and activate different signaling pathways for thermotaxis

Debarun Roy,Vladimir Kiss,Michael Eisenbach,Kohava Levi,Reinat Nevo

doi:10.1038/s41598-019-56846-5

Abstract

Recently, various opsin types, known to be involved in vision, were demonstrated to be present in human and mouse sperm cells and to be involved there in thermosensing for thermotaxis. In vision, each opsin type is restricted to specific cells. The situation in this respect in sperm cells is not known. It is also not known whether or not both signaling pathways, found to function in sperm thermotaxis, are each activated by specific opsins, as in vision. Here we addressed these questions. Choosing rhodopsin and melanopsin as test cases and employing immunocytochemical analysis with antibodies against these opsins, we found that the majority of sperm cells were stained by both antibodies, indicating that most of the cells contained both opsins. By employing mutant mouse sperm cells that do not express melanopsin combined with specific signaling inhibitors, we furthermore demonstrated that rhodopsin and melanopsin each activates a different pathway. Thus, in mammalian sperm thermotaxis, as in vision, rhodopsin and melanopsin each triggers a different signaling pathway but, unlike in vision, both opsin types coexist in the same sperm cells.

Highlights

Various opsin types, known to be involved in vision, were demonstrated to be present in human and mouse sperm cells and to be involved there in thermosensing for thermotaxis
It was speculated that each sperm cell contains multiple opsin types, each type differently distributed in the cell and associated with only one of the two signaling pathways[4]
We found that the majority of sperm cells were stained by both antibodies (Table 1), indicating that most of the cells contained both opsins together

Summary

Introduction

Various opsin types, known to be involved in vision, were demonstrated to be present in human and mouse sperm cells and to be involved there in thermosensing for thermotaxis. A number of different opsins were demonstrated to be present in sperm cells, inhibition of specific opsins significantly reduced the thermotactic response, and sperm thermotaxis of rhodopsin-knockout mice was 70% reduced. This reduction was larger than expected for the elimination of a single thermosensor out of several, suggesting the importance of rhodopsin for thermotaxis and possibly the existence of a lattice-like array of. We put these speculations to the test, employing rhodopsin and melanopsin as test cases

Methods

Results

Conclusion