Towards the simplification of MHC typing protocols: targeting classical MHC class II genes in a passerine, the pied flycatcher Ficedula hypoleuca

<p>Abstract</p> <p>Background</p> <p>Major Histocompatibility Complex (MHC) has drawn the attention of evolutionary biologists due to its importance in crucial biological processes, such as sexual selection and immune response in jawed vertebrates. However, the characterization of classical MHC genes subjected to the effects of natural selection still remains elusive in many vertebrate groups. Here, we have tested the suitability of flanking intron sequences to guide the selective exploration of classical MHC genes driving the co-evolutionary dynamics between pathogens and their passerine (Aves, Order Passeriformes) hosts.</p> <p>Findings</p> <p>Intronic sequences flanking the usually polymorphic exon 2 were isolated from different species using primers sitting on conserved coding regions of MHC class II genes (β chain). Taking the pied flycatcher <it>Ficedula hypoleuca</it> as an example, we demonstrate that careful primer design can evade non-classical MHC gene and pseudogene amplification. At least four polymorphic and expressed loci were co-replicated using a single pair of primers in five non-related individuals (N = 28 alleles). The cross-amplification and preliminary inspection of similar MHC fragments in eight unrelated songbird taxa suggests that similar approaches can also be applied to other species.</p> <p>Conclusions</p> <p>Intron sequences flanking the usually polymorphic exon 2 may assist the specific investigation of classical MHC class II B genes in species characterized by extensive gene duplication and pseudogenization. Importantly, the evasion of non-classical MHC genes with a more specific function and non-functional pseudogenes may accelerate data collection and diminish lab costs. Comprehensive knowledge of gene structure, polymorphism and expression profiles may be useful not only for the selective examination of evolutionarily relevant genes but also to restrict chimera formation by minimizing the number of co-amplifying loci.</p

Multiscale analysis of complex aeronautical structures using robust non-intrusive coupling

International audienceThe multiscale analysis of large composite aeronautical structures involves the development of robust coupling strategies. Among the latter, non-intrusive coupling is attractive, since it is able to consistently connect a global simplified linear model to a local detailed one, using features available in commercial software. Up to now, such coupling methods were still limited to academic situations where global and local meshes are geometrically and/or topologically conforming and of low geometric complexity. To meet the goal of merging a complex non-planar global shell to a local detailed 3D model, an extension of these techniques is proposed to handle meshes of complex shapes that are not only non-matching but also geometrically and topologically non-conforming. The implemented strategy is original and robust: the innovative nature of the approach is to expand the initial local solid model by generating transitional shell meshing. The generated model incorporates two distinct coupling interfaces: (i) non-intrusive global–local coupling and (ii) shell–solid coupling. The multiscale strategy was successfully validated through different numerical experiments using standard Input/Output of a commercial finite element software. In particular, a representative use-case involving a realistic fuselage section of an aircraft was computed