Sensing in the dark: Constructive evolution of the lateral line system in blind populations of Astyanax mexicanus.

Cave-adapted animals evolve a suite of regressive and constructive traits that allow survival in the dark. Most studies aiming at understanding cave animal evolution have focused on the genetics and environmental underpinnings of regressive traits, with special emphasis on vision loss. Possibly as a result of vision loss, other non-visual sensory systems have expanded and compensated in cave species. For instance, in many cave-dwelling fish species, including the blind cavefish of the Mexican tetra, Astyanax mexicanus, a major non-visual mechanosensory system called the lateral line, compensated for vision loss through morphological expansions. While substantial work has shed light on constructive adaptation of this system, there are still many open questions regarding its developmental origin, synaptic plasticity, and overall adaptive value. This review provides a snapshot of the current state of knowledge of lateral line adaption in A. mexicanus, with an emphasis on anatomy, synaptic plasticity, and behavior. Multiple open avenues for future research in this system, and how these can be leveraged as tools for both evolutionary biology and evolutionary medicine, are discussed.

Defining the Unseen: Population-Specific Markers for Astyanax mexicanus Blind Cavefish.

Astyanax mexicanus is an emerging model system used to study development, evolution, and behavior of multiple cavefish populations that have repeatedly evolved from conspecific surface fish. Although surface and cavefish live and breed in the laboratory, there are no rapid methods for distinguishing between different cavefish populations. We present 2 methods for genotyping fish for a total of 16 population-specific markers using methods that are easy and inexpensive to implement in a basic molecular biology laboratory. This resource will help researchers maintain independent stocks within the laboratory and distinguish between fish from different populations.

Convergence on reduced aggression through shared behavioral traits in multiple populations of Astyanax mexicanus.

BACKGROUND: Aggression is observed across the animal kingdom, and benefits animals in a number of ways to increase fitness and promote survival. While aggressive behaviors vary widely across populations and can evolve as an adaptation to a particular environment, the complexity of aggressive behaviors presents a challenge to studying the evolution of aggression. The Mexican tetra, Astyanax mexicanus exists as an aggressive river-dwelling surface form and multiple populations of a blind cave form, some of which exhibit reduced aggression, providing the opportunity to investigate how evolution shapes aggressive behaviors. RESULTS: To define how aggressive behaviors evolve, we performed a high-resolution analysis of multiple social behaviors that occur during aggressive interactions in A. mexicanus. We found that many of the aggression-associated behaviors observed in surface-surface aggressive encounters were reduced or lost in Pachón cavefish. Interestingly, one behavior, circling, was observed more often in cavefish, suggesting evolution of a shift in the types of social behaviors exhibited by cavefish. Further, detailed analysis revealed substantive differences in aggression-related sub-behaviors in independently evolved cavefish populations, suggesting independent evolution of reduced aggression between cave populations. We found that many aggressive behaviors are still present when surface fish fight in the dark, suggesting that these reductions in aggression-associated and escape-associated behaviors in cavefish are likely independent of loss of vision in this species. Further, levels of aggression within populations were largely independent of type of opponent (cave vs. surface) or individual stress levels, measured through quantifying stress-like behaviors, suggesting these behaviors are hardwired and not reflective of population-specific changes in other cave-evolved traits. CONCLUSION: These results reveal that loss of aggression in cavefish evolved through the loss of multiple aggression-associated behaviors and raise the possibility that independent genetic mechanisms underlie changes in each behavior within populations and across populations. Taken together, these findings reveal the complexity of evolution of social behaviors and establish A. mexicanus as a model for investigating the evolutionary and genetic basis of aggressive behavior.

Cnr2 Is Important for Ribbon Synapse Maturation and Function in Hair Cells and Photoreceptors.

The role of the cannabinoid receptor 2 (CNR2) is still poorly described in sensory epithelia. We found strong cnr2 expression in hair cells (HCs) of the inner ear and the lateral line (LL), a superficial sensory structure in fish. Next, we demonstrated that sensory synapses in HCs were severely perturbed in larvae lacking cnr2. Appearance and distribution of presynaptic ribbons and calcium channels (Cav1.3) were profoundly altered in mutant animals. Clustering of membrane-associated guanylate kinase (MAGUK) in post-synaptic densities (PSDs) was also heavily affected, suggesting a role for cnr2 for maintaining the sensory synapse. Furthermore, vesicular trafficking in HCs was strongly perturbed suggesting a retrograde action of the endocannabinoid system (ECs) via cnr2 that was modulating HC mechanotransduction. We found similar perturbations in retinal ribbon synapses. Finally, we showed that larval swimming behaviors after sound and light stimulations were significantly different in mutant animals. Thus, we propose that cnr2 is critical for the processing of sensory information in the developing larva.

Expression patterns of activating transcription factor 5 (atf5a and atf5b) in zebrafish.

The Activating Transcription Factor 5 (ATF5) is a basic leucine-zipper (bZIP) transcription factor (TF) with proposed stress-protective, anti-apoptotic and oncogenic roles which were all established in cell systems. In whole animals, Atf5 function seems highly context dependent. Atf5 is strongly expressed in the rodent nose and mice knockout (KO) pups have defective olfactory sensory neurons (OSNs), smaller olfactory bulbs (OB), while adults are smell deficient. It was therefore proposed that Atf5 plays an important role in maturation and maintenance of OSNs. Atf5 expression was also described in murine liver and bones where it appears to promote differentiation of progenitor cells. By contrast in the rodent brain, Atf5 was first described as uniquely expressed in neuroprogenitors and thus, proposed to drive their proliferation and inhibit their differentiation. However, it was later also found in mature neurons stressing the need for additional work in whole animals. ATF5 is well conserved with two paralogs, atf5a and atf5b in zebrafish. Here, we present the expression patterns for both from 6 h (hpf) to 5day post-fertilization (dpf). We found early expression for both genes, and from 1dpf onwards overlapping expression patterns in the inner ear and the developing liver. In the brain, at 24hpf both atf5a and atf5b were expressed in the forebrain, midbrain, and hindbrain. However, from 2dpf and onwards we only detected atf5a expression namely in the olfactory bulbs, the mesencephalon, and the metencephalon. We further evidenced additional differential expression for atf5a in the sensory neurons of the olfactory organs, and for atf5b in the neuromasts, that form the superficial sensory organ called the lateral line (LL). Our results establish the basis for future functional analyses in this lower vertebrate.

Altered Swimming Behaviors in Zebrafish Larvae Lacking Cannabinoid Receptor 2.

Background and Objectives: The cannabinoid receptor 2 (CB2) was previously implicated in brain functions, including complex behaviors. Here, we assessed the role of CB2 in selected swimming behaviors in zebrafish larvae and developed an in vivo upscalable whole-organism approach for CB2 ligand screening. Experimental Approach: Using CRISPR-Cas9 technology, we generated a novel null allele (cnr2upr1 ) and a stable homozygote-viable loss-of-function (CB2-KO) line. We measured in untreated wild-type and cnr2upr1/upr1 larvae, photo-dependent (swimming) responses (PDR) and center occupancy (CO) to establish quantifiable anxiety-like parameters. Next, we measured PDR alteration and CO variation while exposing wild-type and mutant animals to an anxiolytic drug (valproic acid [VPA]) or to an anxiogenic drug (pentylenetetrazol [PTZ]). Finally, we treated wild-type and mutant larvae with two CB2-specific agonists (JWH-133 and HU-308) and two CB2-specific antagonists, inverse agonists (AM-630 and SR-144528). Results: Untreated CB2-KO showed a different PDR than wild-type larvae as well as a decreased CO. VPA treatments diminished swimming activity in all animals but to a lesser extend in mutants. CO was strongly diminished and even more in mutants. PTZ-induced inverted PDR was significantly stronger in light and weaker in dark periods and the CO lower in PTZ-treated mutants. Finally, two of four tested CB2 ligands had a detectable activity in the assay. Conclusions: We showed that larvae lacking CB2 behave differently in complex behaviors that can be assimilated to anxiety-like behaviors. Mutant larvae responded differently to VPA and PTZ treatments, providing in vivo evidence of CB2 modulating complex behaviors. We also established an upscalable combined genetic/behavioral approach in a whole organism that could be further developed for high-throughput drug discovery platforms.

Estrategias de procedimientos obtenidas con un sistema inteligente para el procesamiento digital de imagenes / Processing strategies obtained from an intelligent system for digital image processing

Se presentan varias estrategias de procedimientos, obtenidas a través de una consulta realizada a un prototipo experimental de sistema inteligente para el procesamiento digital de imágenes. Estas fueron logradas a partir de la naturaleza de la imagen y del objetivo de trabajo sobre ella. El sistema inteligente para el procesamiento digital de imágenes es un pequeño sistema experto o sistema inteligente de propósitos generales en el campo del procesamiento digital de imágenes, que trata aspectos tales como el mejoramiento de imágenes, detección de contornos, eliminación de ruido y un procedimiento para la restauración de imágenes. Se realiza análisis y discusión de las estrategias emitidas por el sistema a partir de la experiencia acumulada en el procesamiento digital de imagenes

Estudio de la proliferación intimal y la lesión arteriosclerótica aplicando el software Madip / Study of intimal thickeninig and the atherosclerotic lesion using the MADIP software

Se estudian 39 aortas de fallecidos necropsiados con edades comprendidas entre 9 y 35 años; 19 del sexo masculino y 20 del femenino, cuyas causas de muerte no estaban relacionadas con enfermedad aterosclerótica. Se establecen grupos de trabajo de acuerdo con las edades y el sexo, con el objetivo de estudiar las características morfométricas de la proliferación intimal difusa (PID) y la lesión aterosclerótica inicial (estría adiposa) utilizando el software MADIP (Morphological Anlayses by Digital Image Processing). Se analizan las posibles diferencias entre el segmento torácico y el abdominal de la aorta según los grupos de estudio, determinando la correlación existente entre la proliferación intimal difusa y la lesión aterosclerótica inicial

Estudio de la proliferación intimal y la lesión arteriosclerótica aplicando el software Madip / Study of intimal thickeninig and the atherosclerotic lesion using the MADIP software

Se estudian 39 aortas de fallecidos necropsiados con edades comprendidas entre 9 y 35 años; 19 del sexo masculino y 20 del femenino, cuyas causas de muerte no estaban relacionadas con enfermedad aterosclerótica. Se establecen grupos de trabajo de acuerdo con las edades y el sexo, con el objetivo de estudiar las características morfométricas de la proliferación intimal difusa (PID) y la lesión aterosclerótica inicial (estría adiposa) utilizando el software MADIP (Morphological Anlayses by Digital Image Processing). Se analizan las posibles diferencias entre el segmento torácico y el abdominal de la aorta según los grupos de estudio, determinando la correlación existente entre la proliferación intimal difusa y la lesión aterosclerótica inicial

Estrategias de procedimientos obtenidas con un sistema inteligente para el procesamiento digital de imagenes / Processing strategies obtained from an intelligent system for digital image processing

Se presentan varias estrategias de procedimientos, obtenidas a través de una consulta realizada a un prototipo experimental de sistema inteligente para el procesamiento digital de imágenes. Estas fueron logradas a partir de la naturaleza de la imagen y del objetivo de trabajo sobre ella. El sistema inteligente para el procesamiento digital de imágenes es un pequeño sistema experto o sistema inteligente de propósitos generales en el campo del procesamiento digital de imágenes, que trata aspectos tales como el mejoramiento de imágenes, detección de contornos, eliminación de ruido y un procedimiento para la restauración de imágenes. Se realiza análisis y discusión de las estrategias emitidas por el sistema a partir de la experiencia acumulada en el procesamiento digital de imagenes.

Un sistema experto para el procesamiento digital de imagenes / An expert system for digital image processing

Se presenta un prototipo experimental de un sistema experto para el procesamiento digital de imágenes de propósitos generales, que trata aspectos como el de mejoramiento, detección de contornos, eliminación de ruido y un procedimiento para la restauración de imágenes. El sistema experto que se propone tiene 2 objetivos fundamentales: testificar la arquitectura de la base de conocimiento, es decir, si el diseño concebido es adecuado y funcional; y comprobar si las estrategias emitidas por él son correctas. Se presenta un ejemplo de estrategia de procesamiento conformada por el sistema, de acuerdo con la naturaleza de una imagen ultrasónica del corazón de un niño, y según un determinado objetivo.