Biology subjects

Couso, J. P.

Publications and source records attributed to Couso, J. P..

4 recordsLinked to original sources

bioRxiv2021

A community-driven roadmap to advance research on translated open reading frames detected by Ribo-seq

Ribosome profiling (Ribo-seq) has catalyzed a paradigm shift in our understanding of the translational vocabulary of the human genome, discovering thousands of translated open reading frames (ORFs) within long non-coding RNAs and presumed untranslated regions of protein-coding genes. However, reference gene annotation projects have been circumspect in their incorporation of these ORFs due to uncertainties about their experimental reproducibility and physiological roles. Yet, it is indisputable that certain Ribo-seq ORFs make stable proteins, others mediate gene regulation, and many have medical implications. Ultimately, the absence of standardized ORF annotation has created a circular problem: while Ribo-seq ORFs remain unannotated by reference biological databases, this lack of characterisation will thwart research efforts examining their roles. Here, we outline the initial stages of a community-led effort supported by GENCODE / Ensembl, HGNC and UniProt to produce a consolidated catalog of human Ribo-seq ORFs.

genomics↗

bioRxiv2019

Pegasus, a small extracellular peptide regulating the short-range diffusion of Wingless

Small Open Reading Frames (smORFs) coding for peptides of less than 100 amino-acids are emerging as a fundamental and pervasive gene class, found in the hundreds of thousands in metazoan genomes. Even though some of these genes are annotated, their function, if any, remains unknown. Here we characterize the function of a smORF encoding a short 80 aa peptide, pegasus (peg), which facilitates Wg diffusion during the development of the Drosophila wing imaginal disc. During wing development, Wg has sequential functions, and in the later stages, when peg is strongly expressed, it patterns the presumptive wing margin. A reduction in Wg protein secretion at this stage produces effects ranging from total abolition of the wing margin to partial loss of bristles and reduction of proneural gene expression. Here we show that the Peg peptide enhances the short-range of Wg diffusion in this context, in order to produce a proper wing margin. We show that CRISPR/Cas9-mediated mutations of pegasus generate wing margin phenotypes, and changes in target gene expression, consistent with a role in Wg signalling. We find that Peg is secreted, and that it co-localizes and co-immunoprecipitates with Wg, suggesting that Peg directly binds Wg in order to enhance its signalling, and our data from fixed and in-vivo Wg gradient measurements supports a model in which this enhancement occurs by increasing diffusion of extracellular Wg. Our results unveil a new element in the regulation of the Wg signalling pathway, and shed light on the functional consequences of the miss-regulation of Wg diffusion in this developmental context, while also reminding us of the functional diversity, and relevance of small open reading frame genes.

developmental biology↗

bioRxiv2019

Developmental regulation of Canonical and small ORF translation from mRNA

Ribosomal profiling has revealed the translation of thousands of sequences outside of annotated protein-coding genes, including small Open Reading Frames of less than 100 codons, and the translational regulation of many genes. Here we have improved Poly-Ribo-Seq and applied it to Drosophila melanogaster embryos to extend the catalogue of in-vivo translated small ORFs, and to reveal the translational regulation of both small and canonical ORFs from mRNAs across embryogenesis. We obtain highly correlated samples across five embryonic stages, with close to 500 million putative ribosomal footprints mapped to mRNAs, and compared them to existing Ribo-Seq and proteomic data. Our analysis reveals, for the first time in Drosophila, footprints mapping to codons in a phased pattern, the hallmark of productive translation, and we propose a simple binomial probability metric to ascertain translation probability. However, our results also reveal reproducible ribosomal binding apparently not resulting in productive translation. This non-productive ribosomal binding seems to be especially prevalent amongst upstream short ORFs located in the 5 mRNA Leaders, and amongst canonical ORFs during the activation of the zygotic translatome at the maternal to zygotic transition. We suggest that this non-productive ribosomal binding might be due to cis-regulatory ribosomal binding, and to defective ribosomal scanning of ORFs outside periods of productive translation. Finally, we show that the main function of upstream short ORFs is to buffer the translation of canonical ORFs, and that in general small ORFs in mRNAs display Poly-Ribo-Seq and bioinformatics markers compatible with an evolutionary transitory state towards full coding function.

genomics↗

bioRxiv2017

Gene regulatory network architecture in different developmental contexts influences the genetic basis of morphological evolution

Convergent phenotypic evolution is often caused by recurrent changes at particular nodes in the underlying gene regulatory networks (GRNs). The genes at such evolutionary hotspots are thought to maximally affect the phenotype with minimal pleiotropic consequences. This has led to the suggestion that if a GRN is understood in sufficient detail, the path of evolution may be predictable. The repeated evolutionary loss of larval trichomes among Drosophila species is caused by the loss of shavenbaby (svb) expression. svb is also required for development of leg trichomes, but the evolutionary gain of trichomes in the naked valley on T2 femurs in Drosophila melanogaster is caused by the loss of microRNA-92a (miR-92a) expression rather than changes in svb. We compared the expression and function of components between the larval and leg trichome GRNs to investigate why the genetic basis of trichome pattern evolution differs in these developmental contexts. We found key differences between the two networks in both the genes employed, and in the regulation and function of common genes. These differences in the GRNs reveal why mutations in svb are unlikely to contribute to leg trichome evolution and how instead miR-92a represents the key evolutionary switch in this context. Our work shows that variability in GRNs across different developmental contexts, as well as whether a morphological feature is lost versus gained, influence the nodes at which a GRN evolves to cause morphological change. Therefore, our findings have important implications for understanding the pathways and predictability of evolution.\n\nAuthor SummaryA major goal of biology is to identify the genetic cause of organismal diversity. Convergent evolution of traits is often caused by changes in the same genes - evolutionary hotspots. shavenbaby is a hotspot for larval trichome loss in Drosophila, however microRNA-92a underlies the gain of leg trichomes. To understand this difference in the genetics of phenotypic evolution, we compared the expression and function of genes in the underlying regulatory networks. We found that the pathway of evolution is influenced by differences in gene regulatory network architecture in different developmental contexts, as well as by whether a trait is lost or gained. Therefore, hotspots in one context may not readily evolve in a different context. This has important implications for understanding the genetic basis of phenotypic change and the predictability of evolution.

evolutionary biology↗