RESUMEN
Genetic robustness, or the ability of an organism to maintain fitness in the presence of harmful mutations, can be achieved via protein feedback loops. Previous work has suggested that organisms may also respond to mutations by transcriptional adaptation, a process by which related gene(s) are upregulated independently of protein feedback loops. However, the prevalence of transcriptional adaptation and its underlying molecular mechanisms are unknown. Here, by analysing several models of transcriptional adaptation in zebrafish and mouse, we uncover a requirement for mutant mRNA degradation. Alleles that fail to transcribe the mutated gene do not exhibit transcriptional adaptation, and these alleles give rise to more severe phenotypes than alleles displaying mutant mRNA decay. Transcriptome analysis in alleles displaying mutant mRNA decay reveals the upregulation of a substantial proportion of the genes that exhibit sequence similarity with the mutated gene's mRNA, suggesting a sequence-dependent mechanism. These findings have implications for our understanding of disease-causing mutations, and will help in the design of mutant alleles with minimal transcriptional adaptation-derived compensation.
Asunto(s)
Adaptación Fisiológica/genética , Mutación , Estabilidad del ARN/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Transcripción Genética/genética , Regulación hacia Arriba/genética , Alelos , Animales , Epigénesis Genética/genética , Histonas/metabolismo , Ratones , Pez Cebra/genéticaRESUMEN
The proteins Oskar (Osk) in Drosophila and Bucky ball (Buc) in zebrafish act as germ plasm organizers. Both proteins recapitulate germ plasm activities but seem to be unique to their animal groups. Here, we discover that Osk and Buc show similar activities during germ cell specification. Drosophila Osk induces additional PGCs in zebrafish. Surprisingly, Osk and Buc do not show homologous protein motifs that would explain their related function. Nonetheless, we detect that both proteins contain stretches of intrinsically disordered regions (IDRs), which seem to be involved in protein aggregation. IDRs are known to rapidly change their sequence during evolution, which might obscure biochemical interaction motifs. Indeed, we show that Buc binds to the known Oskar interactors Vasa protein and nanos mRNA indicating conserved biochemical activities. These data provide a molecular framework for two proteins with unrelated sequence but with equivalent function to assemble a conserved core-complex nucleating germ plasm.
Asunto(s)
Células Germinativas/metabolismo , Animales , Citoplasma/metabolismo , Drosophila/genética , Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Genes Reporteros , Hidrogel de Polietilenoglicol-Dimetacrilato , Proteínas Intrínsecamente Desordenadas/genética , Proteínas Intrínsecamente Desordenadas/metabolismo , Modelos Biológicos , Oocitos/metabolismo , Proteínas de Unión al ARN/metabolismo , Xenopus , Pez CebraRESUMEN
The phenotypes caused by morpholino-mediated interference of gene function in zebrafish are often not observed in the corresponding mutant(s). We took advantage of the availability of a relatively large collection of transcriptomic datasets to identify common signatures that characterize morpholino-injected animals (morphants). In addition to the previously reported activation of tp53 expression, we observed increased expression of the interferon-stimulated genes (ISGs), isg15 and isg20, the cell death pathway gene casp8, and other cellular stress response genes including phlda3, mdm2 and gadd45aa. Studies involving segmentation stage embryos were more likely to show upregulation of these genes. We also found that the expression of these genes could be upregulated by increasing doses of an egfl7 morpholino, or even high doses of the standard control morpholino. Thus, these data show that morpholinos can induce the expression of ISGs in zebrafish embryos and further our understanding of morpholino effects.
Asunto(s)
Interferones/metabolismo , Morfolinos/farmacología , Proteína p53 Supresora de Tumor/genética , Proteínas de Pez Cebra/genética , Animales , Regulación hacia Abajo/efectos de los fármacos , Embrión no Mamífero/metabolismo , Perfilación de la Expresión Génica/métodos , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Regulación del Desarrollo de la Expresión Génica/genética , Técnicas de Silenciamiento del Gen/métodos , Interferones/genética , Morfolinos/metabolismo , Mutación/efectos de los fármacos , Fenotipo , Estrés Fisiológico/inmunología , Estrés Fisiológico/fisiología , Proteína p53 Supresora de Tumor/inmunología , Regulación hacia Arriba/efectos de los fármacos , Pez Cebra/metabolismo , Proteínas de Pez Cebra/inmunología , Proteínas de Pez Cebra/metabolismoRESUMEN
Several recent studies in a number of model systems including zebrafish, Arabidopsis, and mouse have revealed phenotypic differences between knockouts (i.e., mutants) and knockdowns (e.g., antisense-treated animals). These differences have been attributed to a number of reasons including off-target effects of the antisense reagents. An alternative explanation was recently proposed based on a zebrafish study reporting that genetic compensation was observed in egfl7 mutant but not knockdown animals. Dosage compensation was first reported in Drosophila in 1932, and genetic compensation in response to a gene knockout was first reported in yeast in 1969. Since then, genetic compensation has been documented many times in a number of model organisms; however, our understanding of the underlying molecular mechanisms remains limited. In this review, we revisit studies reporting genetic compensation in higher eukaryotes and outline possible molecular mechanisms, which may include both transcriptional and posttranscriptional processes.
Asunto(s)
Compensación de Dosificación (Genética) , Técnicas de Silenciamiento del Gen , Técnicas de Inactivación de Genes , Transcripción Genética , Animales , Arabidopsis/genética , Drosophila/genética , Ratones , Modelos Animales , Proteínas Mutantes/biosíntesis , Proteínas Mutantes/genética , Pez Cebra/genética , Proteínas de Pez Cebra/genéticaRESUMEN
Cells must adapt to environmental changes to maintain homeostasis. One of the most striking environmental adaptations is entry into hibernation during which core body temperature can decrease from 37°C to as low at 4°C. How mammalian cells, which evolved to optimally function within a narrow range of temperatures, adapt to this profound decrease in temperature remains poorly understood. In this study, we conducted the first genome-scale CRISPR-Cas9 screen in cells derived from Syrian hamster, a facultative hibernator, as well as human cells to investigate the genetic basis of cold tolerance in a hibernator and a non-hibernator in an unbiased manner. Both screens independently revealed glutathione peroxidase 4 (GPX4), a selenium-containing enzyme, and associated proteins as critical for cold tolerance. We utilized genetic and pharmacological approaches to demonstrate that GPX4 is active in the cold and its catalytic activity is required for cold tolerance. Furthermore, we show that the role of GPX4 as a suppressor of cold-induced cell death extends across hibernating species, including 13-lined ground squirrels and greater horseshoe bats, highlighting the evolutionary conservation of this mechanism of cold tolerance. This study identifies GPX4 as a central modulator of mammalian cold tolerance and advances our understanding of the evolved mechanisms by which cells mitigate cold-associated damage-one of the most common challenges faced by cells and organisms in nature.
RESUMEN
Transgenerational epigenetic inheritance (TEI) is mostly discussed in the context of physiological or environmental factors. Here, we show intergenerational and transgenerational inheritance of transcriptional adaptation (TA), a process whereby mutant messenger RNA (mRNA) degradation affects gene expression, in nematodes and zebrafish. Wild-type offspring of animals heterozygous for mRNA-destabilizing alleles display increased expression of adapting genes. Notably, offspring of animals heterozygous for nontranscribing alleles do not display this response. Germline-specific mutations are sufficient to induce TA in wild-type offspring, indicating that, at least for some genes, mutations in somatic tissues are not necessary for this process. Microinjecting total RNA from germ cells of TA-displaying heterozygous zebrafish can trigger TA in wild-type embryos and in their progeny, suggesting a model whereby mutant mRNAs in the germline trigger a TA response that can be epigenetically inherited. In sum, this previously unidentified mode of TEI reveals a means by which parental mutations can modulate the offspring's transcriptome.
Asunto(s)
Aclimatación , Pez Cebra , Animales , Pez Cebra/genética , Heterocigoto , Mutación , ARN Mensajero/genéticaRESUMEN
Transcriptional adaptation is a recently described phenomenon by which a mutation in one gene leads to the transcriptional modulation of related genes, termed adapting genes. At the molecular level, it has been proposed that the mutant mRNA, rather than the loss of protein function, activates this response. While several examples of transcriptional adaptation have been reported in zebrafish embryos and in mouse cell lines, it is not known whether this phenomenon is observed across metazoans. Here we report transcriptional adaptation in C. elegans, and find that this process requires factors involved in mutant mRNA decay, as in zebrafish and mouse. We further uncover a requirement for Argonaute proteins and Dicer, factors involved in small RNA maturation and transport into the nucleus. Altogether, these results provide evidence for transcriptional adaptation in C. elegans, a powerful model to further investigate underlying molecular mechanisms.