Characterization of the melanopsin gene (Opn4x) of diurnal and nocturnal snakes

Autor(es)

Hauzman, Einat ^{[1, 2]} ; Kalava, Venkatasushma ^[3] ; Oliveira Bonci, Daniela Maria ^{[1, 2]} ; Ventura, Dora Fix ^{[1, 2]}

Afiliação do(s) autor(es)

^[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

• Tipo de documento: Artigo Científico
• Fonte: BMC Evolutionary Biology; v. 19, n. 1 AUG 28 2019.
• Citações Web of Science: 0

Resumo

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)

• Processo FAPESP: 09/06026-6 - Estudo psicofísico e genético das deficiências da visão de cores em humanos com diferentes patologias
• Beneficiário: Dora Selma Fix Ventura
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 14/26818-2 - Desenvolvimento e implantação de métodos de avaliação visual: aplicações clínicas e em modelos animais
• Beneficiário: Dora Selma Fix Ventura
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 08/58731-2 - A visão como indicador de processos lesivos na retina e no sistema nervoso central
• Beneficiário: Dora Selma Fix Ventura
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 10/51670-8 - Ecologia e evolução do sistema visual de serpentes Caenophidia: estudos comparativos da morfologia retiniana e genética de opsinas
• Beneficiário: Einat Hauzman
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 14/25743-9 - Expressão de opsinas e melanopsinas em retinas de serpentes: genética molecular e imunohistoquímica
• Beneficiário: Einat Hauzman
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado