An annotated CNS transcriptome of the medicinal leech, Hirudo verbana: De novo sequencing to characterize genes associated with nervous system activity.

Adam J. Northcutt,Joshua G. Puhl,Karen A. Mesce,David J. Schulz,Eva K. Fischer,Maurice J. Chacron

doi:10.1371/journal.pone.0201206

Adam J. Northcutt, Joshua G. Puhl + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0201206

Copy DOI

Abstract

The medicinal leech is one of the most venerated model systems for the study of fundamental nervous system principles, ranging from single-cell excitability to complex sensorimotor integration. Yet, molecular analyses have yet to be extensively applied to complement the rich history of electrophysiological study that this animal has received. Here, we generated the first de novo transcriptome assembly from the entire central nervous system of Hirudo verbana, with the goal of providing a molecular resource, as well as to lay the foundation for a comprehensive discovery of genes fundamentally important for neural function. Our assembly generated 107,704 contigs from over 900 million raw reads. Of these 107,704 contigs, 39,047 (36%) were annotated using NCBI’s validated RefSeq sequence database. From this annotated central nervous system transcriptome, we began the process of curating genes related to nervous system function by identifying and characterizing 126 unique ion channel, receptor, transporter, and enzyme contigs. Additionally, we generated sequence counts to estimate the relative abundance of each identified ion channel and receptor contig in the transcriptome through Kallisto mapping. This transcriptome will serve as a valuable community resource for studies investigating the molecular underpinnings of neural function in leech and provide a reference for comparative analyses.

Highlights

Medicinal leeches have long been studied as a model for understanding the neural underpinnings of behavior [1,2,3,4], fundamental electrophysiology principles [5,6], central-pattern generation [7], and metamodulation [8]
Our assembly generated 107,704 contigs from over 900 million raw reads. Of these 107,704 contigs, 39,047 (36%) were annotated using the validated RefSeq sequence database from NCBI (Bethesda, MD, USA). From this central nervous system (CNS) transcriptome, we identified 126 unique ion channels, receptors, transporters, and enzyme contigs related to neural function and determined their relative abundance within the whole CNS
From the sequencing of the entire CNS of H. verbana, 919,249,178 raw reads were generated from 75 bp paired-end Illumina sequencing

Summary

Introduction

Medicinal leeches have long been studied as a model for understanding the neural underpinnings of behavior [1,2,3,4], fundamental electrophysiology principles [5,6], central-pattern generation [7], and metamodulation [8]. Molecular sequence information for the Northwestern European medicinal leech Hirudo medicinalis has more recently been accumulating through studies targeting specific candidate gene sequences [9,10,11,12,13,14], tissue types [15,16], or life stages [17]. The Southeastern European medicinal leech Hirudo verbana has not received the same.

Methods

Results

Discussion

Conclusion