Novel Approach Combining Transcriptional and Evolutionary Signatures to Identify New Multiciliation Genes.

Multiciliogenesis is a complex process that allows the generation of hundreds of motile cilia on the surface of specialized cells, to create fluid flow across epithelial surfaces. Dysfunction of human multiciliated cells is associated with diseases of the brain, airway and reproductive tracts. Despite recent efforts to characterize the transcriptional events responsible for the differentiation of multiciliated cells, a lot of actors remain to be identified. In this work, we capitalize on the ever-growing quantity of high-throughput data to search for new candidate genes involved in multiciliation. After performing a large-scale screening using 10 transcriptomics datasets dedicated to multiciliation, we established a specific evolutionary signature involving Otomorpha fish to use as a criterion to select the most likely targets. Combining both approaches highlighted a list of 114 potential multiciliated candidates. We characterized these genes first by generating protein interaction networks, which showed various clusters of ciliated and multiciliated genes, and then by computing phylogenetic profiles. In the end, we selected 11 poorly characterized genes that seem like particularly promising multiciliated candidates. By combining functional and comparative genomics methods, we developed a novel type of approach to study biological processes and identify new promising candidates linked to that process.

Proteome-Scale Detection of Differential Conservation Patterns at Protein and Subprotein Levels with BLUR.

In the multiomics era, comparative genomics studies based on gene repertoire comparison are increasingly used to investigate evolutionary histories of species, to study genotype-phenotype relations, species adaptation to various environments, or to predict gene function using phylogenetic profiling. However, comparisons of orthologs have highlighted the prevalence of sequence plasticity among species, showing the benefits of combining protein and subprotein levels of analysis to allow for a more comprehensive study of genotype/phenotype correlations. In this article, we introduce a new approach called BLUR (BLAST Unexpected Ranking), capable of detecting genotype divergence or specialization between two related clades at different levels: gain/loss of proteins but also of subprotein regions. These regions can correspond to known domains, uncharacterized regions, or even small motifs. Our method was created to allow two types of research strategies: 1) the comparison of two groups of species with no previous knowledge, with the aim of predicting phenotype differences or specializations between close species or 2) the study of specific phenotypes by comparing species that present the phenotype of interest with species that do not. We designed a website to facilitate the use of BLUR with a possibility of in-depth analysis of the results with various tools, such as functional enrichments, protein-protein interaction networks, and multiple sequence alignments. We applied our method to the study of two different biological pathways and to the comparison of several groups of close species, all with very promising results. BLUR is freely available at http://lbgi.fr/blur/.

OrthoInspector 3.0: open portal for comparative genomics.

OrthoInspector is one of the leading software suites for orthology relations inference. In this paper, we describe a major redesign of the OrthoInspector online resource along with a significant increase in the number of species: 4753 organisms are now covered across the three domains of life, making OrthoInspector the most exhaustive orthology resource to date in terms of covered species (excluding viruses). The new website integrates original data exploration and visualization tools in an ergonomic interface. Distributions of protein orthologs are represented by heatmaps summarizing their evolutionary histories, and proteins with similar profiles can be directly accessed. Two novel tools have been implemented for comparative genomics: a phylogenetic profile search that can be used to find proteins with a specific presence-absence profile and investigate their functions and, inversely, a GO profiling tool aimed at deciphering evolutionary histories of molecular functions, processes or cell components. In addition to the re-designed website, the OrthoInspector resource now provides a REST interface for programmatic access. OrthoInspector 3.0 is available at http://lbgi.fr/orthoinspectorv3.

Alternative dimerization interfaces in the glucocorticoid receptor-α ligand binding domain.

BACKGROUND: Nuclear hormone receptors (NRs) constitute a large family of multi-domain ligand-activated transcription factors. Dimerization is essential for their regulation, and both DNA binding domain (DBD) and ligand binding domain (LBD) are implicated in dimerization. Intriguingly, the glucocorticoid receptor-α (GRα) presents a DBD dimeric architecture similar to that of the homologous estrogen receptor-α (ERα), but an atypical dimeric architecture for the LBD. The physiological relevance of the proposed GRα LBD dimer is a subject of debate. METHODS: We analyzed all GRα LBD homodimers observed in crystals using an energetic analysis based on the PISA and on the MM/PBSA methods and a sequence conservation analysis, using the ERα LBD dimer as a reference point. RESULTS: Several dimeric assemblies were observed for GRα LBD. The assembly generally taken to be physiologically relevant showed weak binding free energy and no significant residue conservation at the contact interface, while an alternative homodimer mediated by both helix 9 and C-terminal residues showed significant binding free energy and residue conservation. However, none of the GRα LBD assemblies found in crystals are as stable or conserved as the canonical ERα LBD dimer. GRα C-terminal sequence (F-domain) forms a steric obstacle to the canonical dimer assembly in all available structures. CONCLUSIONS: Our analysis calls for a re-examination of the currently accepted GRα homodimer structure and experimental investigations of the alternative architectures. GENERAL SIGNIFICANCE: This work questions the validity of the currently accepted architecture. This has implications for interpreting physiological data and for therapeutic design pertaining to glucocorticoid research.