DOI: 10.5061/dryad.s1f22
title: Data from: Transcriptomic analysis of the lesser spotted catshark (Scyliorhinus canicula) pancreas, liver and brain reveals molecular level conservation of vertebrate pancreas function

description: Background: Understanding the evolution of the vertebrate pancreas is key
 to understanding its functions. The chondrichthyes (cartilaginous fish
 such as sharks and rays) have often been suggested to possess the most
 ancient example of a distinct pancreas with both hormonal (endocrine) and
 digestive (exocrine) roles. The lack of genetic, genomic and
 transcriptomic data for cartilaginous fish has hindered a more thorough
 understanding of the molecular-level functions of the chondrichthyan
 pancreas, particularly with respect to their "unusual" energy
 metabolism (where ketone bodies and amino acids are the main oxidative
 fuel source) and their paradoxical ability to both maintain stable blood
 glucose levels and tolerate extensive periods of hypoglycemia. In order to
 shed light on some of these processes, we carried out the first
 large-scale comparative transcriptomic survey of multiple cartilaginous
 fish tissues: the pancreas, brain and liver of the lesser spotted
 catshark, Scyliorhinus canicula. Results: We generated a mutli-tissue
 assembly comprising 86,006 contigs, of which 44,794 were assigned to a
 particular tissue or combination of tissues based on mapping of sequencing
 reads. We have characterised transcripts encoding genes involved in
 insulin regulation, glucose sensing, transcriptional regulation, signaling
 and digestion, as well as many peptide hormone precursors and their
 receptors for the first time. Comparisons to mammalian pancreas
 transcriptomes reveals that mechanisms of glucose sensing and insulin
 regulation used to establish and maintain a stable internal environment
 are conserved across jawed vertebrates and likely pre-date the vertebrate
 radiation. Conservation of pancreatic hormones and genes encoding
 digestive proteins support the single, early evolution of a distinct
 pancreatic gland with endocrine and exocrine functions in jawed
 vertebrates. In addition, we demonstrate that chondrichthyes lack
 pancreatic polypeptide (PP) and that reports of PP in the literature are
 likely due cross-reaction with PYY and/or NPY in the pancreas. A three
 hormone islet organ is therefore the ancestral jawed vertebrate condition,
 later elaborated upon only in the tetrapod lineage. Conclusions: The
 cartilaginous fish are a great untapped resource for the reconstruction of
 patterns and processes of vertebrate evolution and new approaches such as
 those described in this paper will greatly facilitate their incorporation
 into the rank of "model organism".
description: Catshark three tissue
 assemblyTrinity assembly of
 RNA-Seq data derived from pancreas, liver and brain. Trimmed to remove
 contigs &lt;300bp.Sca_all_tissues300.fasCatshark pancreas mapped transcriptsTranscripts mapped to the catshark pancreas, trimmed to remove contigs &lt;300bp.Additional _file_2_pancreas_only300.fastaCatshark brain mapped transcriptsTranscripts mapped to the catshark brain, trimmed to remove contigs &lt;300bp.Additional_file_3_brain_only300.fastaCatshark liver mapped transcriptsTranscripts mapped to the catshark liver, trimmed to remove contigs &lt;300bp.Additional_file_4_liver_only300.fastaCatshark pancreas and brain mapped transcriptsTranscripts mapped to the catshark pancreas and brain, trimmed to remove contigs &lt;300bp.Additional_file_5_pancreas_brain300.fastaCatshark pancreas and liver mapped transcriptsTranscripts mapped to the catshark pancreas and liver, trimmed to remove contigs &lt;300bp.Additional_file_6_pancreas_liver300.fastaCatshark brain and liver mapped transcriptsTranscripts mapped to the catshark brain and liver, trimmed to remove contigs &lt;300bp.Additional_file_7_brain_liver300.fastaCatshark pancreas, liver and brain mapped transcriptsTranscripts mapped to the catshark pancreas, liver and brain, trimmed to remove contigs &lt;300bp.Additional_file_8_pancreas_liver_brain300.fasta