Phylogenetic reclassification of vertebrate melatonin receptors to include Mel1d

The circadian and seasonal actions of melatonin are mediated by high affinity G-protein coupled receptors (melatonin receptors, MTRs), classified into phylogenetically distinct subtypes based on sequence divergence and pharmacological characteristics. Three vertebrate MTR subtypes are currently described: MT1 (MTNR1A), MT2 (MTNR1B), and Mel1c (MTNR1C / GPR50), which exhibit distinct affinities, tissue distributions and signaling properties. We present phylogenetic and comparative genomic analyses supporting a revised classification of the vertebrate MTR family. We demonstrate four ancestral vertebrate MTRs, including a novel molecule hereafter named Mel1d. We reconstructed the evolution of each vertebrate MTR, detailing genetic losses in addition to gains resulting from whole genome duplication events in teleost fishes. We show that Mel1d was lost separately in mammals and birds and has been previously mistaken for an MT1 paralogue. The genetic and functional diversity of vertebrate MTRs is more complex than appreciated, with implications for our understanding of melatonin actions in different taxa. The significance of our findings, including the existence of Mel1d, are discussed in an evolutionary and functional context accommodating a robust phylogenetic assignment of MTR gene family structure

Chip protein U-box domain truncation affects Purkinje neuron morphology and leads to behavioral changes in zebrafish

The ubiquitin ligase CHIP (C-terminus of Hsc70-interacting protein) is encoded by STUB1 and promotes ubiquitination of misfolded and damaged proteins. CHIP deficiency has been linked to several diseases, and mutations in the human STUB1 gene are associated with recessive and dominant forms of spinocerebellar ataxias (SCAR16/SCA48). Here, we examine the effects of impaired CHIP ubiquitin ligase activity in zebrafish (Danio rerio). We characterized the zebrafish stub1 gene and Chip protein, and generated and characterized a zebrafish mutant causing truncation of the Chip functional U-box domain. Zebrafish stub1 has a high degree of conservation with mammalian orthologs and was detected in a wide range of tissues in adult stages, with highest expression in brain, eggs, and testes. In the brain, stub1 mRNA was predominantly detected in the cerebellum, including the Purkinje cell layer and granular layer. Recombinant wild-type zebrafish Chip showed ubiquitin ligase activity highly comparable to human CHIP, while the mutant Chip protein showed impaired ubiquitination of the Hsc70 substrate and Chip itself. In contrast to SCAR16/SCA48 patients, no gross cerebellar atrophy was evident in mutant fish, however, these fish displayed reduced numbers and sizes of Purkinje cell bodies and abnormal organization of Purkinje cell dendrites. Mutant fish also had decreased total 26S proteasome activity in the brain and showed behavioral changes. In conclusion, truncation of the Chip U-box domain leads to impaired ubiquitin ligase activity and behavioral and anatomical changes in zebrafish, illustrating the potential of zebrafish to study STUB1-mediated diseases.publishedVersio

Are Hox Genes Ancestrally Involved in Axial Patterning? Evidence from the Hydrozoan Clytia hemisphaerica (Cnidaria)

Background: The early evolution and diversification of Hox-related genes in eumetazoans has been the subject of conflicting hypotheses concerning the evolutionary conservation of their role in axial patterning and the pre-bilaterian origin of the Hox and ParaHox clusters. The diversification of Hox/ParaHox genes clearly predates the origin of bilaterians. However, the existence of a "Hox code' predating the cnidarian-bilaterian ancestor and supporting the deep homology of axes is more controversial. This assumption was mainly based on the interpretation of Hox expression data from the sea anemone, but growing evidence from other cnidarian taxa puts into question this hypothesis. Methodology/Principal Findings: Hox, ParaHox and Hox-related genes have been investigated here by phylogenetic analysis and in situ hybridisation in Clytia hemisphaerica, an hydrozoan species with medusa and polyp stages alternating in the life cycle. Our phylogenetic analyses do not support an origin of ParaHox and Hox genes by duplication of an ancestral ProtoHox cluster, and reveal a diversification of the cnidarian HOX9-14 genes into three groups called A, B, C. Among the 7 examined genes, only those belonging to the HOX9-14 and the CDX groups exhibit a restricted expression along the oralaboral axis during development and in the planula larva, while the others are expressed in very specialised areas at the medusa stage. Conclusions/Significance: Cross species comparison reveals a strong variability of gene expression along the oral-aboral axis and during the life cycle among cnidarian lineages. The most parsimonious interpretation is that the Hox code, collinearity and conservative role along the antero-posterior axis are bilaterian innovations

Développement et évolution des cellules neurosensorielles chez les cnidaires (apports de l étude de la nématogenèse de la méduse de Clytia hemisphaerica.)

Les cnidaires sont un groupe-clé pour étudier l origine et l évolution des cellules nerveuses. Des marqueurs neuronaux de Bilateria sont exprimés dans le bulbe tentaculaire de la méduse de Clytia hemisphaerica, spécialisé dans la production massive de cellules neurosensorielles, les nématocytes. La dynamique de la nématogenèse du bulbe a été étudiée ; les stades de différenciation y sont répartis selon un gradient proximo-distal, corrélé à un étagement de profils d expression de gènes. La capacité d autonomie du bulbe in vitro en fera un modèle expérimental performant pour réaliser des études fonctionnelles. La pression de décharge de son organite, le nématocyste, est générée par du poly- -glutamate. Différentes données suggèrent que la synthèse de ce polymère rare, intimement associé à l'histoire évolutive des nématocytes, est liée à la co-option d'un gène bactérien acquis par transfert horizontal, et au recrutement secondaire de gènes initialement utilisés pour une fonction nerveuse.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Sulfate homeostasis in Atlantic salmon is associated with differential regulation of salmonid-specific paralogs in gill and kidney

Sulfate (SO2−4) regulation is challenging for euryhaline species as they deal with large fluctuations of SO2−4 during migratory transitions between freshwater (FW) and seawater (SW), while maintaining a stable plasma SO2−4 concentration. Here, we investigated the regulation and potential role of sulfate transporters in Atlantic salmon during the preparative switch from SO2−4 uptake to secretion. A preparatory increase in kidney and gill sodium/potassium ATPase (Nka) enzyme activity during smolt development indicate preparative osmoregulatory changes. In contrast to gill Nka activity a transient decrease in kidney Nka after direct SW exposure was observed and may be a result of reduced glomerular filtration rates and tubular flow through the kidney. In silico analyses revealed that Atlantic salmon genome comprises a single slc13a1 gene and additional salmonid-specific duplications of slc26a1 and slc26a6a, leading to new paralogs, namely the slc26a1a and -b, and slc26a6a1 and -a2. A kidney-specific increase in slc26a6a1 and slc26a1a during smoltification and SW transfer, suggests an important role of these sulfate transporters in the regulatory shift from absorption to secretion in the kidney. Plasma SO2−4 in FW smolts was 0.70 mM, followed by a transient increase to 1.14 ± 0.33 mM 2 days post-SW transfer, further decreasing to 0.69 ± 0.041 mM after 1 month in SW. Our findings support the vital role of the kidney in SO2−4 excretion through the upregulated slc26a6a1, the most likely secretory transport candidate in fish, which together with the slc26a1a transporter likely removes excess SO2−4 , and ultimately enable the regulation of normal plasma SO2−4 levels in SW

Sulfate homeostasis in Atlantic salmon is associated with differential regulation of salmonid-specific paralogs in gill and kidney

Sulfate (SO2−4) regulation is challenging for euryhaline species as they deal with large fluctuations of SO2−4 during migratory transitions between freshwater (FW) and seawater (SW), while maintaining a stable plasma SO2−4 concentration. Here, we investigated the regulation and potential role of sulfate transporters in Atlantic salmon during the preparative switch from SO2−4 uptake to secretion. A prepara-tory increase in kidney and gill sodium/potassium ATPase (Nka) enzyme activity during smolt development indicate preparative osmoregulatory changes. In con-trast to gill Nka activity a transient decrease in kidney Nka after direct SW expo-sure was observed and may be a result of reduced glomerular filtration rates and tubular flow through the kidney. In silico analyses revealed that Atlantic salmon genome comprises a single slc13a1gene and additional salmonid- specific duplica-tions of slc26a1 and slc26a6a, leading to new paralogs, namely the slc26a1a and - b, and slc26a6a1 and - a2. A kidney- specific increase in slc26a6a1 and slc26a1a during smoltification and SW transfer, suggests an important role of these sul-fate transporters in the regulatory shift from absorption to secretion in the kid-ney. Plasma SO2−4 in FW smolts was 0.70mM, followed by a transient increase to 1.14±0.33mM 2days post- SW transfer, further decreasing to 0.69±0.041mM after 1month in SW. Our findings support the vital role of the kidney in SO2−4 ex-cretion through the upregulated slc26a6a1, the most likely secretory transport can-didate in fish, which together with the slc26a1a transporter likely removes excess SO2−4, and ultimately enable the regulation of normal plasma SO2−4 levels in SW

An adhesome comprising laminin, dystroglycan and myosin IIA is required during notochord development in Xenopus laevis.

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Lumpfish Cyclopterus lumpus reproduction: Pituitary gene expression, physiological and morphological changes accompanying gonadal maturation

Lumpfish is the most important cleanerfish species in Atlantic salmon farming. Detailed information on the gonadal maturation process is a prerequisite for year-round production of juvenile lumpfish. In the present study we have described physiological, morphological and endocrine events associated with the annual reproductive cycle in lumpfish of both sexes. Female lumpfish matured at a body weight close to 2 kg and were capable of spawning two egg batches, one in February/March and one in May/June. Male lumpfish could be stripped for sperm most of the year. The appearance of spawning males with high 11-KT concentrations and clearly developed secondary sexual characters was synchronized with female spawning. From the onset of maturation to the periovulatory stages in females, pituitary transcript levels of gnrhr2ba1 and lhb increased in a correlated manner, together with an increase in GSI and in circulating E2 concentrations. In contrast, a high individual variation of fshb transcript levels was observed, potentially reflecting the bimodal oocyte development with oocytes at different developmental stages present in the ovary at the same time. The onset of pubertal testis growth concurred with an increase in pituitary fshb and lhb transcript levels, while plasma 11-KT concentrations increased at later stages, correlating with a gnrhr2ba1 increase. It appears that spermatogenesis and testis growth is regulated by Fsh and can proceed in the presence of low androgen levels.publishedVersio