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Sylvie Retaux - One of the best experts on this subject based on the ideXlab platform.
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Evolution of acoustic communication in blind cavefish
Nature Communications, 2019Co-Authors: Carole Hyacinthe, Joël Attia, Sylvie RetauxAbstract:Acoustic communication allows the exchange of information within specific contexts and during specific behaviors. The blind, cave-adapted and the sighted, river-dwelling morphs of the species Astyanax mexicanus have evolved in markedly different environments. During their evolution in darkness, cavefish underwent a series of morphological, physiological and behavioral changes, allowing the study of adaptation to drastic environmental change. Here we discover that Astyanax is a sonic species, in the laboratory and in the wild, with sound production depending on the social contexts and the type of morph. We characterize one sound, the “Sharp Click”, as a visually-triggered sound produced by dominant surface fish during agonistic behaviors and as a chemosensory-, food odor-triggered sound produced by cavefish during foraging. Sharp Clicks also elicit different reactions in the two morphs in play-back experiments. Our results demonstrate that acoustic communication does exist and has evolved in cavefish, accompanying the evolution of its behaviors. The fish Astyanax mexicanus has divergent cave and river-dwelling eco-morphotypes. Here, Hyacinthe et al. show that cave and river fish communicate sonically, but that the sounds produced and the responses elicited in the two morphs depend differently on the social and behavioral context.
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lens apoptosis in the Astyanax blind cavefish is not triggered by its small size or defects in morphogenesis
PLOS ONE, 2017Co-Authors: Helene Hinaux, Alexandre Alie, Maryline Blin, Laurent Legendre, Gaelle Recher, Sylvie RetauxAbstract:Blindness is a convergent trait in many cave animals of various phyla. Astyanax mexicanus cavefish is one of the best studied cave animals; however the mechanisms underlying eye degeneration in this species are not yet completely understood. The lens seems to play a central role, but only relatively late differentiation defects have been implicated in the cavefish lens apoptosis phenotype so far. Here, we used genetic crosses between Astyanax cavefish and surface fish to confirm that during development, lens size is independent of retina size. We then investigated whether the small size of the cavefish lens could directly cause cell death. Laser ablation experiments of lens placode cells in surface fish embryos showed that a small lens size is not sufficient to trigger lens apoptosis. We further examined potential lens morphogenesis defects through classical histology and live-imaging microscopy. From lens placode to lens ball, we found that lens invagination and formation of the lens epithelium and fiber cells occur normally in cavefish. We conclude that the main and deleterious defect in the Astyanax cavefish lens must concern the molecular control of lens cell function.
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evolutionary genetics of the cavefish Astyanax mexicanus
Advances in Genetics, 2016Co-Authors: Didier Casane, Sylvie RetauxAbstract:Abstract Blind and depigmented fish belonging to the species Astyanax mexicanus are outstanding models for evolutionary genetics. During their evolution in the darkness of caves, they have undergone a number of changes at the morphological, physiological, and behavioral levels, but they can still breed with their river-dwelling conspecifics. The fertile hybrids between these two morphotypes allow forward genetic approaches, from the search of quantitative trait loci to the identification of the mutations underlying the evolution of troglomorphism. We review here the past 30 years of evolutionary genetics on Astyanax : from the first crosses and the discovery of convergent evolution of different Astyanax cavefish populations to the most recent evolutionary transcriptomics and genomics studies that have provided researchers with potential candidate genes to be tested using functional genetic approaches. Although significant progress has been made and some genes have been identified, cavefish have not yet fully revealed the secret of their adaptation to the absence of light. In particular, the genetic determinism of their loss of eyes seems complex and still puzzles researchers. We also discuss future research directions, including searches for the origin of cave alleles and searches for selection genome-wide, as well as the necessary but missing information on the timing of cave colonization by surface fish.
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differences in chemosensory response between eyed and eyeless Astyanax mexicanus of the rio subterraneo cave
Evodevo, 2013Co-Authors: Jonathan Bibliowicz, Luis Espinasa, Masato Yoshizawa, Alexandre Alie, Maryline Blin, Helene Hinaux, Laurent Legendre, Stephane Pere, Sylvie RetauxAbstract:Background In blind cave-dwelling populations of Astyanax mexicanus, several morphological and behavioral shifts occurred during evolution in caves characterized by total and permanent darkness. Previous studies have shown that sensory systems such as the lateral line (mechanosensory) and taste buds (chemosensory) are modified in cavefish. It has long been hypothesized that another chemosensory modality, the olfactory system, might have evolved as well to provide an additional mechanism for food-searching in troglomorphic Astyanax populations.
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de novo sequencing of Astyanax mexicanus surface fish and pachon cavefish transcriptomes reveals enrichment of mutations in cavefish putative eye genes
PLOS ONE, 2013Co-Authors: Helene Hinaux, William R. Jeffery, Julie Poulain, Corinne Da Silva, Celine Noirot, Didier Casane, Sylvie RetauxAbstract:Astyanax mexicanus, a teleost species with surface dwelling (surface fish) and cave adapted (cavefish) morphs, is an important model system in evolutionary developmental biology (evodevo). Astyanax cavefish differ from surface fish in numerous traits, including the enhancement of non-visual sensory systems, and the loss of eyes and pigmentation. The genetic bases for these differences are not fully understood as genomic and transcriptomic data are lacking. We here present de novo transcriptome sequencing of embryonic and larval stages of a surface fish population and a cavefish population originating from the Pachon cave using the Sanger method. This effort represents the first large scale sequence and clone resource for the Astyanax research community. The analysis of these sequences show low levels of polymorphism in cavefish compared to surface fish, confirming previous studies on a small number of genes. A high proportion of the genes mutated in cavefish are known to be expressed in the zebrafish visual system. Such a high number of mutations in cavefish putative eye genes may be explained by relaxed selection for vision during the evolution in the absence of light. Based on these sequence differences, we provide a list of 11 genes that are potential candidates for having a role in cavefish visual system degeneration.
William R. Jeffery - One of the best experts on this subject based on the ideXlab platform.
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Astyanax surface and cave fish morphs.
Evodevo, 2020Co-Authors: William R. JefferyAbstract:The small teleost fish Astyanax mexicanus has emerged as an outstanding model for studying many biological topics in the context of evolution. A major attribute is conspecific surface dwelling (surface fish) and blind cave dwelling (cavefish) morphs that can be raised in the laboratory and spawn large numbers of transparent and synchronously developing embryos. More than 30 cavefish populations have been discovered, mostly in northeastern Mexico, and some are thought to have evolved independently from surface fish ancestors, providing excellent models of parallel and convergent evolution. Cavefish have evolved eye and pigmentation regression, as well as modifications in brain morphology, behaviors, heart regenerative capacity, metabolic processes, and craniofacial organization. Thus, the Astyanax model provides researchers with natural "mutants" to study life in the challenging cave environment. The application of powerful genetic approaches based on hybridization between the two morphs and between the different cavefish populations are key advantages for deciphering the developmental and genetic mechanisms regulating trait evolution. QTL analysis has revealed the genetic architectures of gained and lost traits. In addition, some cavefish traits resemble human diseases, offering novel models for biomedical research. Astyanax research is supported by genome assemblies, transcriptomes, tissue and organ transplantation, gene manipulation and editing, and stable transgenesis, and benefits from a welcoming and interactive research community that conducts integrated community projects and sponsors the International Astyanax Meeting (AIM).
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complex evolutionary and genetic patterns characterize the loss of scleral ossification in the blind cavefish Astyanax mexicanus
PLOS ONE, 2015Co-Authors: Kelly E Oquin, Pooja Doshi, Anastasia Lyon, Emma Hoenemeyer, Masato Yoshizawa, William R. JefferyAbstract:The sclera is the tough outer covering of the eye that provides structural support and helps maintain intraocular pressure. In some fishes, reptiles, and birds, the sclera is reinforced with an additional ring of hyaline cartilage or bone that forms from scleral ossicles. Currently, the evolutionary and genetic basis of scleral ossification is poorly understood, especially in teleost fishes. We assessed scleral ossification among several groups of the Mexican tetra (Astyanax mexicanus), which exhibit both an eyed and eyeless morph. Although eyed Astyanax surface fish have bony sclera similar to other teleosts, the ossicles of blind Astyanax cavefish generally do not form. We first sampled cavefish from multiple independent populations and used ancestral character state reconstructions to determine how many times scleral ossification has been lost. We then confirmed these results by assessing complementation of scleral ossification among the F1 hybrid progeny of two cavefish populations. Finally, we quantified the number of scleral ossicles present among the F2 hybrid progeny of a cross between surface fish and cavefish, and used this information to identify quantitative trait loci (QTL) responsible for this trait. Our results indicate that the loss of scleral ossification is common–but not ubiquitous–among Astyanax cavefish, and that this trait has been convergently lost at least three times. The presence of wild-type, ossified sclera among the F1 hybrid progeny of a cross between different cavefish populations confirms the convergent evolution of this trait. However, a strongly skewed distribution of scleral ossicles found among surface fish x cavefish F2 hybrids suggests that scleral ossification is a threshold trait with a complex genetic basis. Quantitative genetic mapping identified a single QTL for scleral ossification on Astyanax linkage group 1. We estimate that the threshold for this trait is likely determined by at least three genetic factors which may control the severity and onset of lens degeneration in cavefishes. We conclude that complex evolutionary and genetic patterns underlie the loss of scleral ossification in Astyanax cavefish.
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quantitative genetic analysis of retinal degeneration in the blind cavefish Astyanax mexicanus
PLOS ONE, 2013Co-Authors: Kelly E Oquin, Pooja Doshi, Masato Yoshizawa, William R. JefferyAbstract:The retina is the light-sensitive tissue of the eye that facilitates vision. Mutations within genes affecting eye development and retinal function cause a host of degenerative visual diseases, including retinitis pigmentosa and anophthalmia/microphthalmia. The characin fish Astyanax mexicanus includes both eyed (surface fish) and eyeless (cavefish) morphs that initially develop eyes with normal retina; however, early in development, the eyes of cavefish degenerate. Since both surface and cave morphs are members of the same species, they serve as excellent evolutionary mutant models with which to identify genes causing retinal degeneration. In this study, we crossed the eyed and eyeless forms of A. mexicanus and quantified the thickness of individual retinal layers among 115 F2 hybrid progeny. We used next generation sequencing (RAD-seq) and microsatellite mapping to construct a dense genetic map of the Astyanax genome, scan for quantitative trait loci (QTL) affecting retinal thickness, and identify candidate genes within these QTL regions. The map we constructed for Astyanax includes nearly 700 markers assembled into 25 linkage groups. Based on our scans with this map, we identified four QTL, one each associated with the thickness of the ganglion, inner nuclear, outer plexiform, and outer nuclear layers of the retina. For all but one QTL, cavefish alleles resulted in a clear reduction in the thickness of the affected layer. Comparative mapping of genetic markers within each QTL revealed that each QTL corresponds to an approximately 35 Mb region of the zebrafish genome. Within each region, we identified several candidate genes associated with the function of each affected retinal layer. Our study is the first to examine Astyanax retinal degeneration in the context of QTL mapping. The regions we identify serve as a starting point for future studies on the genetics of retinal degeneration and eye disease using the evolutionary mutant model Astyanax.
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de novo sequencing of Astyanax mexicanus surface fish and pachon cavefish transcriptomes reveals enrichment of mutations in cavefish putative eye genes
PLOS ONE, 2013Co-Authors: Helene Hinaux, William R. Jeffery, Julie Poulain, Corinne Da Silva, Celine Noirot, Didier Casane, Sylvie RetauxAbstract:Astyanax mexicanus, a teleost species with surface dwelling (surface fish) and cave adapted (cavefish) morphs, is an important model system in evolutionary developmental biology (evodevo). Astyanax cavefish differ from surface fish in numerous traits, including the enhancement of non-visual sensory systems, and the loss of eyes and pigmentation. The genetic bases for these differences are not fully understood as genomic and transcriptomic data are lacking. We here present de novo transcriptome sequencing of embryonic and larval stages of a surface fish population and a cavefish population originating from the Pachon cave using the Sanger method. This effort represents the first large scale sequence and clone resource for the Astyanax research community. The analysis of these sequences show low levels of polymorphism in cavefish compared to surface fish, confirming previous studies on a small number of genes. A high proportion of the genes mutated in cavefish are known to be expressed in the zebrafish visual system. Such a high number of mutations in cavefish putative eye genes may be explained by relaxed selection for vision during the evolution in the absence of light. Based on these sequence differences, we provide a list of 11 genes that are potential candidates for having a role in cavefish visual system degeneration.
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Non-optical releasers for aggressive behavior in blind and blinded Astyanax (Teleostei, Characidae)
Behavioural Processes, 2005Co-Authors: Luis Espinasa, Yoshiyuki Yamamoto, William R. JefferyAbstract:Prior to this study, it was believed that epigean and hypogean Astyanax differ markedly in their display of agonistic behavior. Research suggested that surface-dwelling individuals were extremely aggressive whereas their blind, cave-dwelling counterparts tended to show little or no aggressive behavior. Aggression in Astyanax was thought to be triggered by visual stimuli because surface fish in a dark environment or surface fish blinded late in life did not show aggression. Here, we demonstrate that surface fish blinded early on in their embryonic development are highly aggressive as adults. We also report the first case of a population of blind cave-dwelling Astyanax that is highly aggressive. We conclude that reduced aggression is not the only evolutionary pathway for troglobitic Astyanax and that there is some degree of developmental plasticity in the releaser of aggression and in the selection of its triggering stimuli.
Klaus Reutter - One of the best experts on this subject based on the ideXlab platform.
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ultrastructure of the taste buds in the blind cave fish Astyanax jordani anoptichthys and the sighted river fish Astyanax mexicanus teleostei characidae
The Journal of Comparative Neurology, 2001Co-Authors: Friederike Boudriot, Klaus ReutterAbstract:This study describes the ultrastructure of the taste buds of the sighted river fish Astyanax mexicanus and of the blind cave fish Astyanax jordani (=Anoptichthys) (Teleostei, Characiformes, Characidae). In Astyanax and Anoptichthys, taste buds occur in the epithelia of the lips, oral cavity, and, in Anoptichthys, lower jaw. Both possess three types of taste buds: type I (elevated), type II (slightly elevated), and type III taste buds (not elevated or sunken). The taste buds are up to 60 μm high and up to 35 μm wide. The taste bud's sensory epithelium consists of 100–130 elongated cells: light cells, dense-cored-vesicles (dcv) -cells, dark cells, and degenerating cells. The dcv-cells are rich in dense-cored vesicles and are described for the first time in a teleostean taste bud. At the taste bud's base, there lie two to three basal cells. The basal cells of type I and type II taste buds have microvillus (spine)-like processes, in contrast to those of type III taste buds. The taste bud's nerve fiber plexus is situated between the bases of the elongated taste bud cells and the basal cells. Afferent synapses occur between dcv-cells and basal cells (presynaptic sides) and axons (postsynaptic side). Indistinct synapses occur between light cells and dark cells (presynaptic sides) and axons (postsynaptic side). The nerve fiber plexes of Anoptichthys type II and type III taste buds contain significantly more axon profiles than those of Astyanax. This may be associated with a compensatory improvement of the sense of taste in the blind, cave-dwelling fish. J. Comp. Neurol. 434:428–444, 2001. © 2001 Wiley-Liss, Inc.
Karine Frehner Kavalco - One of the best experts on this subject based on the ideXlab platform.
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A THIRD CYTOTYPE OF Astyanax aff. fasciatus (TELEOSTEI, CHARACIDAE) FROM THE SÃO FRANCISCO RIVER BASIN
2020Co-Authors: Pierre Rafael Penteado, Karine Frehner Kavalco, Rubens PazzaAbstract:Astyanax is one of the genus most widely distributed throughout the Neotropical region, due to its structure and population density. These features make the genus is extremely specious, with over one hundred species currently described. The objective of this work is to assist in the survey of genetic diversity in the genre, analyzing a population of Astyanax aff. fasciatus, found in Sao Francisco River Basin. Cytogenetic analysis constitute conventional karyotyping, detection of constitutive heterochromatin and the location of ribosomal genes 5S and 18S. Astyanax aff. fasciatus showed 2n = 48 (8M +22 SM +12 ST +6 A), heterochromatin distributed in pericentromeric regions of few chromosomes. In situ hybridization showed interstitial 5S rDNA sites in a pair of metacentric chromosomes and the pericentromeric region of one pair of acrocentric chromosomes. The present data represent a third cytotype of the species Astyanax aff. fasciatus complex for the basin concerned, and their situation and perspectives are discussed.
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trends in karyotype evolution in Astyanax teleostei characiformes characidae insights from molecular data
Frontiers in Genetics, 2018Co-Authors: Rubens Pazza, Jorge Abdala Dergam, Karine Frehner KavalcoAbstract:The study of patterns and evolutionary processes in neotropical fish is not always an easy task due the wide distribution of major fish groups in large and extensive river basins. Thus, it is not always possible to detect or correlate possible effects of chromosome rearrangements in the evolution of biodiversity. In the Astyanax genus, chromosome data obtained since the 1970s have shown evidence of cryptic species, karyotypic plasticity, supernumerary chromosomes, triploidies, and minor chromosomal rearrangements. In the present work, we map and discuss the main chromosomal events compatible with the molecular evolution of the genus Astyanax (Characiformes, Characidae) using mitochondrial DNA sequence data, in the search for major chromosome evolutionary trends within this taxon.
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Parallel evolution evidenced by molecular data in the banded-tetra (Astyanax fasciatus)
Biochemical Systematics and Ecology, 2017Co-Authors: Rubens Pazza, Letícia Aparecida Cruvinel, Karine Frehner KavalcoAbstract:Astyanax is well known as a model for developmental biology studies, particularly with regard to Mexico's cave populations. More than 130 species of Astyanax are already known, most of which live in South America. The occurrence of cryptic species and species complexes elucidated by chromosomal and genetic studies demonstrates that the relationship between morphology and molecular evolution is quite complex within this group. In this work, we demonstrate that morphology does not follow the path of vicariant processes observed in Astyanax fasciatus populations, which separated about three million years ago, although molecular data suggests its separation in two species.
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Cytogenetical analyses in four species of the genus Astyanax (Pisces, Characidae) from Paraíba do Sul River Basin
Caryologia, 2012Co-Authors: Karine Frehner Kavalco, Orlando Moreira-filhoAbstract:Abstract Cytogenetical data in four species of the genus Asytanax from Paraitinga river, Paraiba do Sul river basin, Brazil, are presented. Astyanax scabripinnis and Astyanax parahybae from other localities were previously cytogenetically described, however the karyotypes of Astyanax intermedius and Astyanax giton are described for the first time. A. scabripinnis, A. intermedius, and A. giton showed 2n=50 chromosomes, which are different from to A. parahybae, that presented 2n=48 chromosomes. The four species revealed multiple rDNA sites, as detected by silver nitrate staining and FISH-18S. The present data are discussed based on karyotypes and NOR peculiarities, biological aspects of the analyzed species, and their evolutionary consequences.
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comparative cytogenetics and molecular phylogeography in the group Astyanax altiparanae Astyanax aff bimaculatus teleostei characidae
Cytogenetic and Genome Research, 2011Co-Authors: Karine Frehner Kavalco, Rubens Pazza, Karina De Oliveira Brandao, Caroline Garcia, Lurdes Foresti De AlmeidatoledoAbstract:The genus Astyanax comprises small characin fish of the neotropical region. The so-called ‘yellow-tailed characins’ compose one of the most widely distributed Astyanax
Fausto Foresti - One of the best experts on this subject based on the ideXlab platform.
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Cytogenetic characterization of a supernumerary chromosome segment and of B-chromosomes in Astyanax scabripinnis (Teleostei, Characidae)
Genetica, 2020Co-Authors: Edson Luis Maistro, Claudio Oliveira, Fausto ForestiAbstract:The chromosome complement of a local population of Astyanax scabripinnis in Brazil was investigated with emphasis on the study of the heterochromatin attached to the A-chromosomes and present in the macro B-chromosome. Analysis after C-banding, silver and CMA3 staining, incorporation of 5-bromo-2′-deoxyuridine and chromosome digestion with nine restriction endonucleases revealed that the heterochromatin in the B-chromosomes was different from that found in the A-chromosomes. A polymorphism due to the presence of a supernumerary heterochromatic chromosome segment was observed in the population investigated. Some aspects related to the origin of the heterochromatin polymorphism in Astyanax scabripinnis are discussed.
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Cytogenetic markers as a tool for characterization of hybrids of Astyanax Baird & Girard, 1854 and Hyphessobrycon Eigenmann, 1907.
Comparative Cytogenetics, 2020Co-Authors: Caio Augusto Gomes Goes, Fausto Foresti, Roberto Ferreira Artoni, Sandro Natal Daniel, Diogo Teruo Hashimoto, Lucas Henrique Piva, George Shigueki Yasui, Fábio Porto-forestiAbstract:Astyanax Baird et Girard, 1854, is one of the largest genera in the family Characidae and comprises 177 valid species. This genus has been the focus of cytogenetic studies primarily owing to the presence of B chromosomes and high karyotypic diversity among different populations. The intense genetic variability in Astyanax is one of the factors responsible for the occurrence of species complexes, which are groups (1) with certain difficulties in establishing common genetic pools or (2) belonging to different cryptic species. To evaluate cytogenetic marker inheritance and the possibility of the identification of these hybrids, this study aimed to describe cytogenetic hybrids from three strains of species of the genera Astyanax and Hyphessobrycon Eigenmann, 1908. A. lacustris Lutken, 1875, A. schubarti Britski, 1964, A. fasciatus Cuvier, 1819, and H. anisitsi Eigenmann, 1907 were used to generate three hybrid lineages. The diploid number, heterochromatin sites, and ribosomal genes (18S and 5S rDNA) of the parental strains and the hybrids were analyzed. The results indicated that the three hybrid lineages had cytogenetic markers of both parents, presenting Mendelian inheritance. However, differences in distribution of heterochromatic blocks were observed between the hybrids and the parent strains. Our results allowed the identification of the hybrid strains based on the cytogenetic markers applied, reinforcing the efficiency of cytogenetic markers as tools for identification and indicating that such events may increase the karyotypic diversity in the genera Astyanax and Hyphessobrycon.
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highlighting Astyanax species diversity through dna barcoding
PLOS ONE, 2016Co-Authors: Bruno Cesar Rossini, Fausto Foresti, Carlos Alexandre Miranda Oliveira, Filipe Augusto Goncalves De Melo, Vinicius De Arau Jo Bertaco, Juan Diaz M De Astarloa, Juan Jose Rosso, Claudio OliveiraAbstract:DNA barcoding has been used extensively to solve taxonomic questions and identify new species. Neotropical fishes are found in a wide variety of shapes and sizes, with a large number of species yet to be described, many of which are very difficult to identify. Characidae is the most species-rich family of the Characiformes, and many of its genera are affected by taxonomic uncertainties, including the widely-distributed, species-rich genus Astyanax. In this study, we present an extensive analysis of Astyanax covering almost its entire area of occurrence, based on DNA barcoding. The use of different approaches (ABGD, GMYC and BIN) to the clustering of the sequences revealed ample consistency in the results obtained by the initial cutoff value of 2% divergence for putative species in the Neighbor-Joining analysis using the Kimura-2-parameter model. The results indicate the existence of five Astyanax lineages. Some groups, such as that composed by the trans-Andean forms, are mostly composed of well-defined species, and in others a number of nominal species are clustered together, hampering the delimitation of species, which in many cases proved impossible. The results confirm the extreme complexity of the systematics of the genus Astyanax and show that DNA barcoding can be an useful tool to address these complexes questions.
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New Insights into Karyotypic Relationships Among Populations of Astyanax bockmanni (Teleostei, Characiformes) of Different Watersheds
Zebrafish, 2015Co-Authors: Sandro Natal Daniel, Fausto Foresti, Manolo Penitente, Diogo Teruo Hashimoto, Duílio Mazzoni Zerbinato De Andrade Silva, Fábio Porto-forestiAbstract:Abstract The fish constitute about 50% of all vertebrates, including a wide morphological and biological diversity, where the genus Astyanax is the most common and diverse, as described in virtually all freshwater environments. By occupying a basal position in the phylogeny of vertebrates, fish are an extremely favorable group for cytogenetic and evolutionary studies. The karyotype found in genus Astyanax diversity may involve a number of polymorphisms, which may be related to ploidy and karyotypic macrostructure, presence of B chromosomes, heterochromatin polymorphisms, and location of ribosomal genes. Nevertheless, the relationship between populations of this species is still poorly studied. Thus, the present work aimed to investigate karyotype variation, chromosomal relationships, and the behavior of 5S and 18S ribosomal genes in six populations of Astyanax bockmanni. The results confirmed the diploid number of 50 chromosomes in all the populations sampled, with the occurrence of one supernumerary chro...
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chromosomal mapping of repetitive dna sequences in five species of Astyanax characiformes characidae reveals independent location of u1 and u2 snrna sites and association of u1 snrna and 5s rdna
Cytogenetic and Genome Research, 2015Co-Authors: Duilio M Z A Silva, Claudio Oliveira, Ricardo Utsunomia, Jose Carlos Pansonatoalves, Fausto ForestiAbstract:Astyanax is a genus of Characidae fishes currently composed of 155 valid species. Previous cytogenetic studies revealed high chromosomal diversification among them, and several studies have been performed using traditional cytogenetic techniques to investigate karyotypes and chromosomal locations of 18S and 5S rDNA genes. However, only a few studies are currently available about other repetitive sequences. Here, the chromosomal location of small nuclear RNA genes, identified as U1 and U2 snRNA clusters, was established and compared to the distribution of 5S rDNA and histone clusters in 5 Astyanax species (A. paranae, A. fasciatus, A. bockmanni, A. altiparanae, and A. jordani) using FISH. The cytogenetic mapping of U1 and U2 snRNA demonstrated a conserved pattern in the number of sites per genome independent of the location in Astyanax species. The location of the U1 snRNA gene was frequently associated with 5S rDNA sequences, indicating a possible interaction between the distinct repetitive DNA families. Finally, comparisons involving the location of U1 and U2 snRNA clusters in the chromosomes of Astyanax species revealed a very diverse pattern, suggesting that many rearrangements have occurred during the diversification process of this group.