Nanos Is Expressed in Somatic and Germline Tissue during Larval and Post-Larval Development of the Annelid Alitta virens.

Roman P Kostyuchenko

doi:10.3390/genes13020270

Abstract

Nanos is a translational regulator that is involved in germline development in a number of diverse animals and is also involved in somatic patterning in several model organisms, including insects. Neither germline development nor somatic stem cell lines/undifferentiated multipotent cells have been characterized in the development of the annelid Alitta virens, nor is the mechanism of germ/stem-line specification generally well-understood in annelids. Here, I have cloned an Avi-nanos ortholog from A. virens and determined the spatial and temporal expression of Nanos. The results revealed that transcripts of nanos are expressed during differentiation of multiple tissues, including those that are derived from the 2d and 4d cells. In late embryonic stages and during larval development, these transcripts are expressed in the presumptive brain, ventral nerve cord, mesodermal bands, putative primordial germ cells (PGCs), and developing foregut and hindgut. During metamorphosis of the nectochaete larva into a juvenile worm, a posterior growth zone consisting of nanos-positive cells is established, and the PGCs begin to migrate. Later, the PGCs stop migrating and form a cluster of four nanos-expressing cells located immediately behind the jaws (segments 4–5). During posterior regeneration following caudal amputation, a robust Avi-nanos expression appears de novo at the site of injury and further accompanies all steps of regeneration. The obtained data suggest that blastemal cells are mostly derived from cells of the segment adjacent to the amputation site; this is consistent with the idea that the cluster of PGCs do not participate in regeneration.

Highlights

This study examines nanos-related genes in Alitta virens, a member of the phylum Annelida
A single nanos fragment was identified in the A. virens transcriptome and isolated by gene-specific PCR from A. virens cDNA; the cDNA sequence is available from GenBank under accession number OL456152
In this work an ortholog of the nanos gene family (Avi-nanos) was isolated from the annelid A. virens, and its developmental expression patterns were examined by wholemount in situ hybridization during the embryonic, larval, and juvenile stages, and during posterior regeneration

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Nanos was originally discovered and studied in Drosophila melanogaster [1]. Its homologs encode proteins belonging to a highly conserved protein family found in both vertebrates and invertebrates. One to four nanos genes have been identified across all investigated animal species [2]. Nanos is a translational repressor characterized by a C-terminal domain comprised of two CCHC zinc finger motifs [2]

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Conclusion