Limits...
Transcriptomic analysis of the lesser spotted catshark (Scyliorhinus canicula) pancreas, liver and brain reveals molecular level conservation of vertebrate pancreas function.

Mulley JF, Hargreaves AD, Hegarty MJ, Heller RS, Swain MT - BMC Genomics (2014)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Bangor University, Brambell Building, Deiniol Road, Bangor, Gwynedd LL57 2UW, United Kingdom. j.mulley@bangor.ac.uk.

ABSTRACT

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".

Show MeSH

Related in: MedlinePlus

Amino acid alignment of vertebrate Peptide YY (PYY), Neuropeptide Y (NPY) and Pancreatic polypeptide (PP) sequences. Genbank accession numbers are given in square brackets. Sca, Scyliorhinus canicula (lesser spotted catshark); Sac, Squalus acanthias (spiny dogfish); Ler, Leucoraja erinacea (little skate); Cmi, Callorhinchus milii (elephant shark); Hsa, Homo sapiens (human); Lfl, Lampetra planeri (brook lamprey); Loc, Leucoraja ocellata (winter skate).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4362833&req=5

Fig7: Amino acid alignment of vertebrate Peptide YY (PYY), Neuropeptide Y (NPY) and Pancreatic polypeptide (PP) sequences. Genbank accession numbers are given in square brackets. Sca, Scyliorhinus canicula (lesser spotted catshark); Sac, Squalus acanthias (spiny dogfish); Ler, Leucoraja erinacea (little skate); Cmi, Callorhinchus milii (elephant shark); Hsa, Homo sapiens (human); Lfl, Lampetra planeri (brook lamprey); Loc, Leucoraja ocellata (winter skate).

Mentions: The presence of PP and γ-cells are key aspects of current schemes for the mode of vertebrate pancreas evolution[1–3, 35]. However, it has been known for some time that PP is tetrapod-specific, produced via duplication of the Peptide YY gene sometime prior to the divergence of this lineage[36, 37] and there is therefore a discrepancy between the findings of decades of immunohistochemical research and data from molecular genetic studies and analyses of vertebrate whole genome sequences. We have identified transcripts of two members of the Neuropeptide Y family (which includes Neuropeptide Y (NPY), Peptide YY (PYY) and Pancreatic polypeptide (PP)) in our dataset - a PYY gene expressed in pancreas and brain and a NPY gene expressed only in brain (Figure 7, both sequences are identical to published catshark sequences for PYY and NPY (accessions P69095[38], AAB23237[14]). We therefore suggest that older immunohistochemical studies which claimed to have detected PP+ cells in the cartilaginous fish pancreas may have in fact been relying on antisera that cross-reacted with PYY. A focus on the (often brief) methods sections of several key historical papers revealed that they in fact used the same anti-PP antibody, produced by Ronald Chance at Eli Lily in the 1970’s[16, 39, 40]. It therefore appears that this antibody was detecting PYY in the pancreas of cartilaginous fish and that these initial papers and various subsequent papers have repeatedly been cited until the presence of PP in cartilaginous fish is considered to be established fact. In other cases, the misidentification of sequenced peptides has added to the confusion[38].Figure 7


Transcriptomic analysis of the lesser spotted catshark (Scyliorhinus canicula) pancreas, liver and brain reveals molecular level conservation of vertebrate pancreas function.

Mulley JF, Hargreaves AD, Hegarty MJ, Heller RS, Swain MT - BMC Genomics (2014)

Amino acid alignment of vertebrate Peptide YY (PYY), Neuropeptide Y (NPY) and Pancreatic polypeptide (PP) sequences. Genbank accession numbers are given in square brackets. Sca, Scyliorhinus canicula (lesser spotted catshark); Sac, Squalus acanthias (spiny dogfish); Ler, Leucoraja erinacea (little skate); Cmi, Callorhinchus milii (elephant shark); Hsa, Homo sapiens (human); Lfl, Lampetra planeri (brook lamprey); Loc, Leucoraja ocellata (winter skate).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4362833&req=5

Fig7: Amino acid alignment of vertebrate Peptide YY (PYY), Neuropeptide Y (NPY) and Pancreatic polypeptide (PP) sequences. Genbank accession numbers are given in square brackets. Sca, Scyliorhinus canicula (lesser spotted catshark); Sac, Squalus acanthias (spiny dogfish); Ler, Leucoraja erinacea (little skate); Cmi, Callorhinchus milii (elephant shark); Hsa, Homo sapiens (human); Lfl, Lampetra planeri (brook lamprey); Loc, Leucoraja ocellata (winter skate).
Mentions: The presence of PP and γ-cells are key aspects of current schemes for the mode of vertebrate pancreas evolution[1–3, 35]. However, it has been known for some time that PP is tetrapod-specific, produced via duplication of the Peptide YY gene sometime prior to the divergence of this lineage[36, 37] and there is therefore a discrepancy between the findings of decades of immunohistochemical research and data from molecular genetic studies and analyses of vertebrate whole genome sequences. We have identified transcripts of two members of the Neuropeptide Y family (which includes Neuropeptide Y (NPY), Peptide YY (PYY) and Pancreatic polypeptide (PP)) in our dataset - a PYY gene expressed in pancreas and brain and a NPY gene expressed only in brain (Figure 7, both sequences are identical to published catshark sequences for PYY and NPY (accessions P69095[38], AAB23237[14]). We therefore suggest that older immunohistochemical studies which claimed to have detected PP+ cells in the cartilaginous fish pancreas may have in fact been relying on antisera that cross-reacted with PYY. A focus on the (often brief) methods sections of several key historical papers revealed that they in fact used the same anti-PP antibody, produced by Ronald Chance at Eli Lily in the 1970’s[16, 39, 40]. It therefore appears that this antibody was detecting PYY in the pancreas of cartilaginous fish and that these initial papers and various subsequent papers have repeatedly been cited until the presence of PP in cartilaginous fish is considered to be established fact. In other cases, the misidentification of sequenced peptides has added to the confusion[38].Figure 7

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Bangor University, Brambell Building, Deiniol Road, Bangor, Gwynedd LL57 2UW, United Kingdom. j.mulley@bangor.ac.uk.

ABSTRACT

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".

Show MeSH
Related in: MedlinePlus