Project description:Genetic compensation by transcriptional modulation of related gene(s) (also known as transcriptional adaptation) has been reported in numerous systems1-3; however, whether and how such a response can be activated in the absence of protein feedback loops is unknown. Here, we develop and analyze several models of transcriptional adaptation in zebrafish and mouse that we show are not caused by loss of protein function. We find that the increase in transcript levels is due to enhanced transcription, and observe a correlation between the levels of mutant mRNA decay and transcriptional upregulation of related genes. To assess the role of mutant mRNA degradation in triggering transcriptional adaptation, we use genetic and pharmacological approaches and find that mRNA degradation is indeed required for this process. Notably, uncapped RNAs, themselves subjected to rapid degradation, can also induce transcriptional adaptation. Next, we generate alleles that fail to transcribe the mutated gene and find that they do not show transcriptional adaptation, and exhibit more severe phenotypes than those observed in alleles displaying mutant mRNA decay. Transcriptome analysis of these different alleles reveals the upregulation of hundreds of genes with enrichment for those showing sequence similarity with the mutated gene's mRNA, suggesting a model whereby mRNA degradation products induce the response via sequence similarity. These results expand the role of the mRNA surveillance machinery in buffering against mutations by triggering the transcriptional upregulation of related genes. Besides implications for our understanding of disease-causing mutations, our findings will help design mutant alleles with minimal transcriptional adaptation-derived compensation.
Project description:A phenomenon of genetic compensation is commonly observed when an organism with a disease-bearing mutation does not show phenotypic penetrance due to compensatory gene expression changes. Reports have spread showing the absence of disease phenotypes in stable knockout models, but not in transient knockdown models. As such, these incidents present a challenge for the disease modeling field, although a deeper understanding of genetic compensation may also hold the key for novel therapeutic interventions. In our study we created a knockout model of slc25a46 gene, which is a recently discovered important player in mitochondrial dynamics and deleterious mutations in which are known to cause peripheral neuropathy, optic atrophy and cerebellar ataxia. We report a case of genetic compensation in the fourth generation (F4) of slc25a46 knockout zebrafish mutant, in contrast to a penetrant disease phenotype in the first generation (F0) slc25a46 mosaic mutant (crispant), generated with CRISPR/Cas-9 technology. We show that F0 crispant phenotype is specific and rescuable. By performing mRNA sequencing, we define significant changes in slc25a46 F4 mutant’s gene expression profile, which are nearly not present in F0 crispants. We find that among the top candidates for the phenotypic compensation anxa6 gene stands out as a functionally relevant player in mitochondrial dynamics. We also find that our genetic compensation case does not arise from previously identified mechanisms driven by mutant mRNA decay. Our study serves as an important contribution to the understanding of phenomenon of genetic compensation and presents novel insights on Slc25a46 function. Furthermore, our study provides the evidence for the efficiency of F0 CRISPR screens for disease candidate genes, which may advance the field of functional genetics.
Project description:This SuperSeries is composed of the following subset Series: GSE36341: mRNA degradation in Mycobacterium tuberculosis under aerobic conditions GSE36342: mRNA degradation in Mycobacterium smegmatis under aerobic conditions GSE36343: mRNA degradation in Mycobacterium tuberculosis during cold and hypoxic stress GSE36344: mRNA degradation in Mycobacterium tuberculosis with DosR ectopically induced Refer to individual Series
Project description:Understanding buffering mechanisms for various perturbations is essential for understanding robustness in cellular systems. Protein-level dosage compensation, which arises when changes in gene copy number do not translate linearly into protein level, is one mechanism for buffering against genetic perturbations. Here, we present an approach to identify genes with dosage compensation by increasing the copy number of individual genes using the genetic tug-of-war technique. Our screen of chromosome I suggests that dosage-compensated genes constitute approximately 10% of the genome and consist predominantly of subunits of multi-protein complexes. Importantly, because subunit levels are regulated in a stoichiometry-dependent manner, dosage compensation plays a crucial role in maintaining subunit stoichiometries. Indeed, we observed changes in the levels of a complex when its subunit stoichiometries were perturbed. We further analyzed compensation mechanisms using a proteasome-defective mutant as well as ribosome profiling, which provided strong evidence for compensation by ubiquitin-dependent degradation but not reduced translational efficiency. Thus, our study provides a systematic understanding of dosage compensation and highlights that this post-translational regulation is a critical aspect of robustness in cellular systems.