Instituto de Ecología y Biodiversidad (IEB)

Spatial maps and oscillations in the healthy hippocampus of octodon degus, a natural model of sporadic Alzheimer’s disease

2023-11-16T15:08:29Z

Spatial maps and oscillations in the healthy hippocampus of octodon degus, a natural model of sporadic Alzheimer’s disease Mugnaini, Matias; Polania Caviedes, Diana Marcela; Díaz, Yannina; Ezquer, Marcelo; Ezquer, Fernando; Deacon, Robert M. J.; Cogram, Patricia; Kropf, Emilio The Octodon degus is a South American rodent that is receiving increased attention as a potential model of aging and sporadic late-onset Alzheimer's disease (AD). Impairments in spatial memory tasks in Octodon degus have been reported in relation to either advanced AD-like disease or hippocampal lesion, opening the way to investigate how the function of hippocampal networks affects behavior across AD stages. However, no characterization of hippocampal electrophysiology exists in this species. Here we describe in young, healthy specimens the activity of neurons and local field potential rhythms during spatial navigation tasks with and without objects. Our findings show similarities between the Octodon degus and laboratory rodents. First, place cells with characteristics similar to those found in rats and mice exist in the CA1 subfield of the Octodon degus. Second, the introduction of objects elicits novelty-related exploration and an increase in activity of CA1 cells, with location specific and unspecific components. Third, oscillations of the local field potential are organized according to their spectral content into bands similar to those found in laboratory rodents. These results suggest a common framework of underlying mechanisms, opening the way to future studies of hippocampal dysfunction in this species associated to aging and disease.

Positive selection over the mitochondrial genome and its role in the diversification of gentoo penguins in response to adaptation in isolation

2023-08-22T21:11:10Z

Positive selection over the mitochondrial genome and its role in the diversification of gentoo penguins in response to adaptation in isolation Noll Vergara, Daly Katherina; León, F.; Brandt, D.; Pistorius, P.; Le Bohec, C.; Bonadonna, F.; Trathan, P. N.; Barbosa, A.; Raya Rey, A.; Dantas, G. P. M.; Bowie, R. C. K.; Poulin, Elie Albert; Viana, J. A. Although mitochondrial DNA has been widely used in phylogeography, evidence has emerged that factors such as climate, food availability, and environmental pressures that produce high levels of stress can exert a strong influence on mitochondrial genomes, to the point of promoting the persistence of certain genotypes in order to compensate for the metabolic requirements of the local environment. As recently discovered, the gentoo penguins (Pygoscelis papua) comprise four highly divergent lineages across their distribution spanning the Antarctic and sub-Antarctic regions. Gentoo penguins therefore represent a suitable animal model to study adaptive processes across divergent environments. Based on 62 mitogenomes that we obtained from nine locations spanning all four gentoo penguin lineages, we demonstrated lineage-specific nucleotide substitutions for various genes, but only lineage-specific amino acid replacements for the ND1 and ND5 protein-coding genes. Purifying selection (dN/dS<1) is the main driving force in the protein-coding genes that shape the diversity of mitogenomes in gentoo penguins. Positive selection (dN/dS>1) was mostly present in codons of the Complex I (NADH genes), supported by two different codon-based methods at the ND1 and ND4 in the most divergent lineages, the eastern gentoo penguin from Crozet and Marion Islands and the southern gentoo penguin from Antarctica respectively. Additionally, ND5 and ATP6 were under selection in the branches of the phylogeny involving all gentoo penguins except the eastern lineage. Our study suggests that local adaptation of gentoo penguins has emerged as a response to environmental variability promoting the fixation of mitochondrial haplotypes in a non-random manner. Mitogenome adaptation is thus likely to have been associated with gentoo penguin diversification across the Southern Ocean and to have promoted their survival in extreme environments such as Antarctica. Such selective processes on the mitochondrial genome may also be responsible for the discordance detected between nuclear- and mitochondrial-based phylogenies of gentoo penguin lineages.

Role of ROX1, SKN7, and YAP6 stress transcription factors in the production of secondary metabolites in xanthophyllomyces dendrorhous

2023-06-14T21:12:07Z

Role of ROX1, SKN7, and YAP6 stress transcription factors in the production of secondary metabolites in xanthophyllomyces dendrorhous Martínez Moya, Pilar; Campusano, Sebastián; Sepúlveda, Dionisia; Paradela Elizalde, Alberto; Alcaíno Gorman, Jennifer Cecilia; Baeza Cancino, Marcelo Enrique; Cifuentes, Víctor Xanthophyllomyces dendrorhous is a natural source of astaxanthin and mycosporines. This yeast has been isolated from high and cold mountainous regions around the world, and the production of these secondary metabolites may be a survival strategy against the stress conditions present in its environment. Biosynthesis of astaxanthin is regulated by catabolic repression through the interaction between MIG1 and corepressor CYC8–TUP1. To evaluate the role of the stress-associated transcription factors SKN7, ROX1, and YAP6, we employed an omic and phenotypic approach. Null mutants were constructed and grown in two fermentable carbon sources. The yeast proteome and transcriptome were quantified by iTRAQ and RNA-seq, respectively. The total carotenoid, sterol, and mycosporine contents were determined and compared to the wild-type strain. Each mutant strain showed significant metabolic changes compared to the wild type that were correlated to its phenotype. In a metabolic context, the principal pathways affected were glycolysis/gluconeogenesis, the pentose phosphate (PP) pathway, and the citrate (TCA) cycle. Additionally, fatty acid synthesis was affected. The absence of ROX1 generated a significant decline in carotenoid production. In contrast, a rise in mycosporine and sterol synthesis was shown in the absence of the transcription factors SKN7 and YAP6, respectively.

Evidence of low within-pair genetic relatedness in a relict population of Thorn-tailed Rayadito despite long-term isolation

2022-07-15T14:14:20Z

Evidence of low within-pair genetic relatedness in a relict population of Thorn-tailed Rayadito despite long-term isolation Botero Delgadillo, Esteban; Quirici, Verónica; Ippi, Silvina; Vásquez, Rodrigo A.; Kempenaers, Bart Investigating whether mating patterns are biased in relation to kinship in isolated populations can provide a better understanding of the occurrence of inbreeding avoidance mechanisms in wild populations. Here, we report on the genetic relatedness (r) among breeding pairs in a relict population of Thorn-tailed Rayadito (Aphrastura spinicauda) in north-central Chile that has experienced a long-term history of isolation. We used simulations based on 8 years of data to assess whether mating is random with respect to relatedness. We found that mean and median population values of pair relatedness tended to be lower than randomly generated values, suggesting that mating is not random with respect to kinship. We hypothesize that female-biased dispersal is the main mechanism reducing the likelihood of mating among kin, and that the proportion of related pairs (i.e., r > 0.125) in the study population (25%) would presumably be higher in the absence of sex-biased dispersal. The occurrence of other mechanisms such as extra-pair copulations, delayed breeding, and active inbreeding avoidance through kin discrimination cannot be dismissed and require further study.