| Full text | |
| Author(s): |
Hauzman, Einat
[1, 2]
;
Kalava, Venkatasushma
[3]
;
Oliveira Bonci, Daniela Maria
[1, 2]
;
Ventura, Dora Fix
[1, 2]
Total Authors: 4
|
| Affiliation: | [1] Inst Israelita Ensino & Pesquisa Albert Einstein, Sao Paulo - Brazil
[2] Univ Sao Paulo, Dept Psicol Expt, Inst Psicol, Av Prof Mello Moraes 1721, Bloco A, Sala D9, BR-05508030 Sao Paulo, SP - Brazil
[3] Christian Bros Univ, Memphis, TN - USA
Total Affiliations: 3
|
| Document type: | Journal article |
| Source: | BMC Evolutionary Biology; v. 19, n. 1 AUG 28 2019. |
| Web of Science Citations: | 0 |
| Abstract | |
Background A number of non-visual responses to light in vertebrates, such as circadian rhythm control and pupillary light reflex, are mediated by melanopsins, G-protein coupled membrane receptors, conjugated to a retinal chromophore. In non-mammalian vertebrates, melanopsin expression is variable within the retina and extra-ocular tissues. Two paralog melanopsin genes were classified in vertebrates, Opn4x and Opn4m. Snakes are highly diversified vertebrates with a wide range of daily activity patterns, which raises questions about differences in structure, function and expression pattern of their melanopsin genes. In this study, we analyzed the melanopsin genes expressed in the retinas of 18 snake species from three families (Viperidae, Elapidae, and Colubridae), and also investigated extra-retinal tissue expression. Results Phylogenetic analysis revealed that the amplified gene belongs to the Opn4x group, and no expression of the Opn4m was found. The same paralog is expressed in the iris, but no extra-ocular expression was detected. Molecular evolutionary analysis indicated that melanopsins are evolving primarily under strong purifying selection, although lower evolutionary constraint was detected in snake lineages (omega = 0.2), compared to non-snake Opn4x and Opn4m (omega = 0.1). Statistical analysis of selective constraint suggests that snake phylogenetic relationships have driven stronger effects on melanopsin evolution, than the species activity pattern. In situ hybridization revealed the presence of melanopsin within cells in the outer and inner nuclear layers, in the ganglion cell layer, and intense labeling in the optic nerve. Conclusions The loss of the Opn4m gene and extra-ocular photosensitive tissues in snakes may be associated with a prolonged nocturnal/mesopic bottleneck in the early history of snake evolution. The presence of melanopsin-containing cells in all retinal nuclear layers indicates a globally photosensitive retina, and the expression in classic photoreceptor cells suggest a regionalized co-expression of melanopsin and visual opsins. (AU) | |
| FAPESP's process: | 09/06026-6 - Psychophysical and genetic study of color vision deficiency in humans with different pathologies |
| Grantee: | Dora Selma Fix Ventura |
| Support Opportunities: | Regular Research Grants |
| FAPESP's process: | 14/26818-2 - Development and implementation of visual evaluation methods: clinical applications and animal models |
| Grantee: | Dora Selma Fix Ventura |
| Support Opportunities: | Research Projects - Thematic Grants |
| FAPESP's process: | 08/58731-2 - Vision as a sensitive indicator of conditions threatening retinal and central nervous system function |
| Grantee: | Dora Selma Fix Ventura |
| Support Opportunities: | Research Projects - Thematic Grants |
| FAPESP's process: | 14/25743-9 - Expression of opsins and melanopsins in snakes' retinas: molecular genetics and immunohistochemistry |
| Grantee: | Einat Hauzman |
| Support Opportunities: | Scholarships in Brazil - Post-Doctoral |