RESUMEN
Quantifying the impacts of inbreeding and genetic drift on fitness traits in fragmented populations is becoming a major goal in conservation biology. Such impacts occur at different levels and involve different sets of loci. Genetic drift randomly fixes slightly deleterious alleles leading to different fixation load among populations. By contrast, inbreeding depression arises from highly deleterious alleles in segregation within a population and creates variation among individuals. A popular approach is to measure correlations between molecular variation and phenotypic performances. This approach has been mainly used at the individual level to detect inbreeding depression within populations and sometimes at the population level but without consideration about the genetic processes measured. For the first time, we used in this study a molecular approach considering both the interpopulation and intrapopulation level to discriminate the relative importance of inbreeding depression vs. fixation load in isolated and non-fragmented populations of European tree frog (Hyla arborea), complemented with interpopulational crosses. We demonstrated that the positive correlations observed between genetic heterozygosity and larval performances on merged data were mainly caused by co-variations in genetic diversity and fixation load among populations rather than by inbreeding depression and segregating deleterious alleles within populations. Such a method is highly relevant in a conservation perspective because, depending on how populations lose fitness (inbreeding vs. fixation load), specific management actions may be designed to improve the persistence of populations.
Asunto(s)
Anuros/genética , Alelos , Animales , Demografía , Flujo Genético , Aptitud Genética , Variación Genética , Heterocigoto , Endogamia , Larva/genética , Estadística como AsuntoRESUMEN
Histone macroH2A, which is a subtype of histone H2A, possesses a histone H2A-like portion fused to a relatively long non-histone portion. MacroH2A has been shown to associate preferentially with the inactive X chromosome [1]. To investigate the specificity of this association, the nuclear distribution of macroH2A was compared with that of regular core histones. In normal human female fibroblasts, all anti-histone antibodies that were tested (including anti-macroH2A antibody) preferentially labeled the inactive X chromosome. Moreover, when expressed as green fluorescent protein (GFP) fusions, both histone H2A and macroH2A were concentrated in the Barr body. These data clearly show the presence of a higher density of nucleosomes in the inactive X chromosome. Accordingly, the specificity of the macroH2A association with the inactive X chromosome should be reconsidered. While investigating the role of macroH2A, we found that the proximity of the non-histone region of macroH2A to a promoter could lead to a specific repression of transcription, suggesting that the incorporation of macroH2A into chromatin might help to establish the stable pattern of gene expression in differentiated cells.
Asunto(s)
Histonas/metabolismo , Nucleosomas/metabolismo , Cromatina Sexual/metabolismo , Cromosoma X/metabolismo , Femenino , Fibroblastos , Histonas/genética , Humanos , Hibridación Fluorescente in Situ , Sondas ARN , ARN Largo no Codificante , ARN no Traducido/genética , ARN no Traducido/metabolismo , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Cromatina Sexual/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
The major protein zero (MPZ) is involved in peripheral myelin folding. Using nested reverse transcription-PCR, we amplified several fragments of MPZ mRNAs in white blood cells and in peripheral nerve tissue. Cloning of PCR products revealed the existence of three alternative splicing patterns: one resulted in the complete loss of exon 3 and two others induced partial skipping of the exon 3 sequence. All three alternative splicing mechanisms produced a frame-shift and created an identical premature stop codon in exon 4. We conclude that the existence of these MPZ RNA transcript variants may be the result of deliberate splicing decisions and may have functional implications in the cell.
Asunto(s)
Empalme Alternativo , Leucocitos/química , Proteína P0 de la Mielina/genética , Sistema Nervioso Periférico/química , Actinas/genética , Adulto , Enfermedad de Charcot-Marie-Tooth/genética , Codón de Terminación , Cartilla de ADN , Exones/fisiología , Humanos , Masculino , Persona de Mediana Edad , Proteína P0 de la Mielina/metabolismo , Especificidad de Órganos , Sistema Nervioso Periférico/citología , Reacción en Cadena de la Polimerasa , Polimorfismo Genético , ARN/genética , ARN/metabolismo , Transcripción GenéticaRESUMEN
A male bus-driver aged 45 had a proboscoid mass on the tip of his nose removed after three year's duration of the disease. Microscopically, the tumour appeared to be a myxoma with marked mucus accumulation extending subepidermally and leading to the formation of lacunes lined with fibroblasts.