Expression Analysis of Cnidarian-Specific Neuropeptides in a Sea Anemone Unveils an Apical-Organ-Associated Nerve Net That Disintegrates at Metamorphosis

Neuropeptides are ancient neuronal signaling molecules that have diversified across Cnidaria (e.g., jellyfish, corals, and sea anemones) and its sister group Bilateria (e.g., vertebrates, insects, and worms). Over the course of neuropeptide evolution emerged lineage-specific neuropeptides, but their roles in the evolution and diversification of nervous system function remain enigmatic. As a step toward filling in this knowledge gap, we investigated the expression pattern of a cnidarian-specific neuropeptide—RPamide—during the development of the starlet sea anemone Nematostella vectensis, using in situ hybridization and immunohistochemistry. We show that RPamide precursor transcripts first occur during gastrulation in scattered epithelial cells of the aboral ectoderm. These RPamide-positive epithelial cells exhibit a spindle-shaped, sensory-cell-like morphology, and extend basal neuronal processes that form a nerve net in the aboral ectoderm of the free-swimming planula larva. At the aboral end, RPamide-positive sensory cells become integrated into the developing apical organ that forms a bundle of long cilia referred to as the apical tuft. Later during planula development, RPamide expression becomes evident in sensory cells in the oral ectoderm of the body column and pharynx, and in the developing endodermal nervous system. At metamorphosis into a polyp, the RPamide-positive sensory nerve net in the aboral ectoderm degenerates by apoptosis, and RPamide expression begins i...

Source: Frontiers in Endocrinology - February 18, 2020 Category: Endocrinology Source Type: research