| 1. |
- Abalo, Xesus, 1976-, et al.
(författare)
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Circadian regulation of phosphodiesterase 6 genes in zebrafish differs between cones and rods : Implications for photopic and scotopic vision
- 2020
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Ingår i: Vision Research. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0042-6989 .- 1878-5646. ; 166, s. 43-51
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Tidskriftsartikel (refereegranskat)abstract
- A correlation is known to exist between visual sensitivity and oscillations in red opsin and rhodopsin gene expression in zebrafish, both regulated by the clock gene. This indicates that an endogenous circadian clock regulates behavioural visual sensitivity, apart from the regulation exerted by the pineal organ. However, the specific mechanisms for cones (photopic vision) and rods (scotopic vision) are poorly understood. In this work, we performed gene expression, cosinor and immunohistochemical analyses to investigate other key genes involved in light perception, encoding the different subunits of phosphodiesterase pde6 and transducin G alpha(T), in constant lighting conditions and compared to normal light-dark conditions. We found that cones display prominent circadian oscillations in mRNA levels for the inhibitory subunit gene pde6ha that could contribute to the regulation of photopic sensitivity by preventing overstimulation in photopic conditions. In rods, the mRNA levels of the inhibitory subunit gene pde6ga oscillate under normal conditions and dampen down in constant light but continue oscillating in constant darkness. There is an increase in total relative expression for pde6gb in constant conditions. These observations, together with previous data, suggest a complex regulation of the scotopic sensitivity involving endogenous and non-endogenous components, possibly present also in other teleost species. The G alpha(T) genes do not display mRNA oscillations and therefore may not be essential for the circadian regulation of photosensitivity. In summary, our results support different regulation for the zebrafish photopic and scotopic sensitivities and suggest circadian regulation of pde6ha as a key factor regulating photopic sensitivity, while the regulatory mechanisms in rods appear to be more complex.
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| 2. |
- Lagman, David, 1987-, et al.
(författare)
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Ancient multiplicity in cyclic nucleotide-gated (CNG) cation channel repertoire was reduced in the ancestor of Olfactores before reexpansion by whole genome duplications in vertebrates
- 2022
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 17:12
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Tidskriftsartikel (refereegranskat)abstract
- Cyclic nucleotide-gated (CNG) cation channels are important heterotetrameric proteins in the retina, with different subunit composition in cone and rod photoreceptor cells: three CNGA3 and one CNGB3 in cones and three CNGA1 and one CNGB1 in rods. CNGA and CNGB subunits form separate subfamilies. We have analyzed the evolution of the CNG gene family in metazoans, with special focus on vertebrates by using sequence-based phylogeny and conservation of chromosomal synteny to deduce paralogons resulting from the early vertebrate whole genome duplications (WGDs). Our analyses show, unexpectedly, that the CNGA subfamily had four sister subfamilies in the ancestor of bilaterians and cnidarians that we named CNGC, CNGD, CNGE and CNGF. Of these, CNGC, CNGE and CNGF were lost in the ancestor of Olfactores while CNGD was lost in the vertebrate ancestor. The remaining CNGA and CNGB genes were expanded by a local duplication of CNGA and the subsequent chromosome duplications in the basal vertebrate WGD events. Upon some losses, this resulted in the gnathostome ancestor having three members in the visual CNGA subfamily (CNGA1-3), a single CNGA4 gene, and two members in the CNGB subfamily (CNGB1 and CNGB3). The nature of chromosomal rearrangements in the vertebrate CNGA paralogon was resolved by including the genomes of a non-teleost actinopterygian and an elasmobranch. After the teleost-specific WGD, additional duplicates were generated and retained for CNGA1, CNGA2, CNGA3 and CNGB1. Furthermore, teleosts retain a local duplicate of CNGB3. The retention of duplicated CNG genes is explained by their subfunctionalisation and photoreceptor-specific expression. In conclusion, this study provides evidence for four previously unknown CNG subfamilies in metazoans and further evidence that the early vertebrate WGD events were instrumental in the evolution of the vertebrate visual and central nervous systems.
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| 3. |
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| 4. |
- Lagman, David, 1987-
(författare)
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Evolution of Vertebrate Vision by Means of Whole Genome Duplications : Zebrafish as a Model for Gene Specialisation
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 5. |
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| 6. |
- Landin, Jenny, et al.
(författare)
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Oxytocin Receptors Regulate Social Preference in Zebrafish.
- 2020
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- With a strong tendency to socialise, the zebrafish is a useful model to study social behaviour, with implications for better treatments of social impairments, for instance in autism spectrum disorders. Although oxytocin is crucial for social behaviour in mammals, the importance of the fish orthologue - isotocin or zebrafish oxytocin (zOT) - for social behaviour in zebrafish is unclear. The aims of this study were firstly, to elucidate the receptor specificity of zOT and the related vasotocin or zebrafish vasopressin (zVP; the orthologue of mammalian vasopressin) and the nonpeptidergic oxytocin receptor antagonist L-368,899, and secondly to investigate if L-368,899 inhibits social preference in zebrafish. The potencies of ligands were evaluated for zOT/zVP family receptors in HEK293 cells. Adult and larval zebrafish were treated with L-368,899 or vehicle and subsequently assessed for social behaviour and anxiety (adults only). The antagonist L-368,899 specifically inhibited the two zOT receptors, but not the two zVP-1 receptors. The antagonist decreased social preference in adult and larval zebrafish. It did not affect anxiety in adults. These results indicate that endogenous zOT, and possibly zVP, is involved in social behaviour in zebrafish via either or both of the two zOT receptors, and show promise for future explorations of the anatomy and evolution of networks underlying social behaviour.
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