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Expansion of transducin subunit gene families in early vertebrate tetraploidizations
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Pharmacology. Uppsala University, Science for Life Laboratory, SciLifeLab.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Pharmacology. Uppsala University, Science for Life Laboratory, SciLifeLab.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Pharmacology. Uppsala University, Science for Life Laboratory, SciLifeLab.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Pharmacology. Uppsala University, Science for Life Laboratory, SciLifeLab.
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2012 (English)In: Genomics, ISSN 0888-7543, E-ISSN 1089-8646, Vol. 100, no 4, 203-211 p.Article in journal (Refereed) Published
Abstract [en]

Hundreds of gene families expanded in the early vertebrate tetraploidizations including many gene families in the phototransduction cascade. We have investigated the evolution of the heterotrimeric G-proteins of photoreceptors, the transducins, in relation to these events using both phylogenetic analyses and synteny comparisons. Three alpha subunit genes were identified in amniotes and the coelacanth, GNAT1-3; two of these were identified in amphibians and teleost fish, GNAT1 and GNAT2. Most tetrapods have four beta genes, GNB1-4, and teleosts have additional duplicates. Finally, three gamma genes were identified in mammals, GNGT1, GNG11 and GNGT2. Of these, GNGT1 and GNGT2 were found in the other vertebrates. In frog and zebrafish additional duplicates of GNGT2 were identified. Our analyses show all three transducin families expanded during the early vertebrate tetraploidizations and the beta and gamma families gained additional copies in the teleost-specific genome duplication. This suggests that the tetraploidizations contributed to visual specialisations.

Place, publisher, year, edition, pages
2012. Vol. 100, no 4, 203-211 p.
Keyword [en]
G-protein, Gene duplication, Phototransduction, Teleost fish, Tetraploidization, Transducin
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:uu:diva-181018DOI: 10.1016/j.ygeno.2012.07.005ISI: 000308731600001OAI: oai:DiVA.org:uu-181018DiVA: diva2:552692
Available from: 2012-09-14 Created: 2012-09-14 Last updated: 2015-03-11Bibliographically approved
In thesis
1. Evolution of Vertebrate Endocrine and Neuronal Gene Families: Focus on Pituitary and Retina
Open this publication in new window or tab >>Evolution of Vertebrate Endocrine and Neuronal Gene Families: Focus on Pituitary and Retina
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The duplication of genes followed by selection is perhaps the most prominent way in which molecular biological systems gain multiplicity, diversity and functional complexity in evolution. Whole genome duplications (WGDs) therefore have the potential of generating an extraordinary amount of evolutionary innovation. It is now accepted that the vertebrate lineage has gone through two rounds of WGD in its early stages, after the divergence of invertebrate chordates and before the emergence of jawed vertebrates. These basal vertebrate WGDs are called 2R for two rounds of whole genome duplication. An additional WGD called 3R occurred early in the evolution of teleost fishes, before the radiation of this species-rich group. This thesis describes the evolution of several endocrine and neuronal gene families in relation to the vertebrate WGDs, through a comparative genomic approach including both phylogenetic analyses and chromosomal location data across a wide range of vertebrate taxa.

These results show that numerous endocrine gene families have expanded in 2R and in several cases also in 3R. These include the gene families of oxytocin and vasopressin receptors (OT/VP-R), somatostatin receptors (SSTR) and insulin-like growth factor binding proteins (IGFBP). For the OT/VP-R and SSTR families, previously undescribed subtypes were identified. The protein hormone family that includes growth hormone (GH), prolactin (PRL) and somatolactin (SL) acquired a new PRL gene in 2R, however the origins of GH, PRL and SL likely predate 2R. The corresponding family of receptors diversified during different time periods through a combination of local duplications and 3R.

Neuronal gene families of the visual system have also expanded in 2R and 3R. The results presented here demonstrate that the vertebrate repertoire of visual opsin genes arose in 2R as part of chromosomal blocks that also include the OT/VP-R genes. The gene families including the transducin alpha, beta and gamma subunits also arose in 2R, hinting at the importance of these events in the diversification and specialization of phototransduction cascades for rods and cones.

Thus, the whole genome duplications have been important contributors to the evolution of both vision and endocrine regulation in the vertebrates.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 55 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 856
Keyword
phylogenetics, evolution, molecular evolution, gene family evolution, genome duplication, gene duplication, oxytocin receptor, vasopressin receptor, visual opsin, transducin, growth hormone, prolactin, somatolactin, growth hormone receptor, prolactin receptor, somatostatin receptor, SSTR, IGFBP, evolution, molekylär evolution, fylogeni
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-191829 (URN)978-91-554-8579-5 (ISBN)
Public defence
2013-03-01, B7:101a, Uppsala Biomedical Centre, BMC, Husargatan 3, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2013-02-07 Created: 2013-01-14 Last updated: 2013-04-02
2. Evolution of Vertebrate Vision by Means of Whole Genome Duplications: Zebrafish as a Model for Gene Specialisation
Open this publication in new window or tab >>Evolution of Vertebrate Vision by Means of Whole Genome Duplications: Zebrafish as a Model for Gene Specialisation
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The signalling cascade of rods and cones use different but related protein components. Rods and cones, emerged in the common ancestor of vertebrates around 500 million years ago around when two whole genome duplications took place, named 1R and 2R. These generated a large number of additional genes that could evolve new or more specialised functions. A third event, 3R, occurred in the ancestor of teleost fish. 

This thesis describes extensive phylogenetic and comparative synteny analyses of the opsins, transducin and phosphodiesterase (PDE6) of this cascade by including data from a wide selection of vertebrates. The expression of the zebrafish genes was also investigated. The results show that genes for these proteins duplicated in 1R and 2R as well as some in 3R.

Expression analyses of the zebrafish genes revealed additional specialisations for the 3R gene duplicates. The transducin beta subunit genes, gnb1a and gnb1b, show co-localisation in rods but are expressed at different levels. Gnb3a and gnb3b show different expression in the adult retina with low expression of gnb3a and expression of gnb3b in cones of the dorso-medial retina. The transducin gamma subunit genes gngt2a and gngt2b are expressed in the ventral and dorso-medial retina respectively. The both of PDE6 gamma subunit genes, pde6ga and pde6gb are both expressed in rods but pde6ga shows rhythmic changes of expression with low daytime levels. Pde6ha and pde6hb are expressed in cones however pde6ha show high daytime expression. All investigated transducin and PDE6 subunit genes, but gnb1b, were also expressed in the adult pineal complex or at some point during development.

These results provide compelling evidence that the 1R and 2R genome duplications facilitated the evolution of rods and cones by generating gene duplicates that could evolve distinct expression and function. This supports existence of colour vision before the origin of vertebrates, elaboration of this in the early vertebrate ancestor, along with origin of the black-and-white dim-light vision of rods. Furthermore, the different expression patterns observed in the zebrafish retina for teleost 3R duplicates demonstrate multiple additional specialisations. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 57 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1070
Keyword
phylogenetics, evolution, vision, visual opsin, transducin, PDE6, genome duplications, subfunctionalisation
National Category
Biological Sciences
Research subject
Medical Science
Identifiers
urn:nbn:se:uu:diva-242781 (URN)978-91-554-9155-0 (ISBN)
Public defence
2015-03-20, B:41, Biomedicinskt centrum, Husargatan 3, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2015-02-26 Created: 2015-02-02 Last updated: 2015-03-11

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