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Myogenesis is an evolutionarily conserved process. Little known, however, is how the morphology of each muscle is determined, such that movements relying upon contraction of many muscles are both precise and coordinated. Each Drosophila larval muscle is a single multinucleated fibre whose morphology reflects expression of distinctive identity Transcription Factors (iTFs). By deleting transcription cis-regulatory modules of one iTF, Collier, we generated viable muscle identity mutants, allowing live imaging and locomotion assays. We show that both selection of muscle attachment sites and muscle/muscle matching is intrinsic to muscle identity and requires transcriptional reprogramming of syncytial nuclei. Live-imaging shows that the staggered muscle pattern involves attraction to tendon cells and heterotypic muscle-muscle adhesion. Unbalance leads to formation of branched muscles, and this correlates with locomotor behavior deficit. Thus, engineering Drosophila muscle identity mutants allows to investigate, in vivo, physiological and mechanical properties of abnormal muscles., eLife digest Each muscle in the body has a unique size, shape and set of attachment points. Animals need all of their muscles to have the correct identity to help maintain posture and control movement. A specific set of proteins, called transcription factors, co-ordinate and regulate gene activity in cells so that each muscle develops in the right way. To create a muscle, multiple precursor cells fuse together to form a muscle fibre, which then elongates and attaches to specific sites. Correct attachment is critical so that the fibre is properly oriented. When this process goes wrong, for example in disease, muscle fibres sometimes attach to the wrong site; they become branched and cannot work properly. Collier is a transcription factor protein that controls muscle identity in the fruit fly Drosophila melanogaster. However, like many transcription factors, Collier also has several other roles throughout the body. This made it difficult to evaluate the effect of the protein on the formation of specific muscles. Here, Carayon et al. managed to selectively deactivate Collier in just one muscle per body section in the larvae of fruit flies. This showed that the transcription factor is needed throughout muscle development; in particular, it is required for muscle fibres to select the correct attachment sites, and to be properly oriented. Affected muscles showed an altered orientation, with branched fibres attaching to the wrong site. Even minor changes, which only affect a single muscle from each body segment, greatly impaired the movement of the larvae. The work by Carayon et al. offers a new approach to the study of muscular conditions. Branched muscles are seen in severe human illnesses such as Duchenne muscular dystrophy. Studying the impact of these changes in a living animal could help to understand how this disease progress, and how it can be prevented.

Alary muscles (AMs) have been described as a component of the cardiac system in various arthropods. Lineage-related thoracic muscles (TARMs), linking the exoskeleton to specific gut regions, have recently been discovered in Drosophila. Asymmetrical attachments of AMs and TARMs, to the exoskeleton on one side, and internal organs on the other, suggested an architectural function in moving larvae. Here, we analysed AMs and TARMs striated organisation, and imaged their atypical deformability in crawling larvae. We then selectively eliminated AMs and TARMs by targeted apoptosis. Elimination of AMs revealed that AMs are required for suspending the heart in proper intra-hemocelic position and opening of the heart lumen, and constrain the curvature of the trachea, the respiratory system, during crawling; TARMs are required for proper positioning of visceral organs and efficient food transit. AM/TARM cardiac versus visceral attachment depends on Hox control, with visceral attachment being the ground state. TARMs and AMs are the first example of multinucleate striated muscles connecting the skeleton to the cardiac and visceral systems in bilaterians, with multiple physiological functions.

This paper presents the main results drawn from the syntactic part of Temporal@ODIL, a project whose objective is the construction of a temporally annotated corpus of spontaneous speech for French. We describe ODIL_Syntax, a freely distributed constituency treebank on which our temporal annotation is grounded. The syntactic annotation was performed on Contemplata, a Web-based annotation platform developed specifically for our project, which is also freely distributed and which integrates a syntactic parser, allowing a semiautomatic annotation. This paper gives a description of the annotation guidelines and the annotation procedure using Contemplata, as well as a statistical description of our corpus, compared with the French Treebank, the largest constituency-based resource for written French, Cet article présente les principaux résultats de la partie syntaxique du projet Temporal@ODIL, une initiative visant la construction d'un corpus de français parlé spontané annoté en temporalité. Nous présentons ici ODIL_Syntax, corpus arboré en constituants sur lequel s'appuie l'annotation temporelle et qui est diffusé librement sous licence Creative Commons. ODIL_Syntax a été créé à l'aide de Contemplata, une plateforme Web d'annotation développée spécifiquement dans le cadre du projet, diffusée elle aussi librement et qui présente l'intérêt de permettre une annotation semi-automatique utilisant un analyseur syntaxique. L'article décrit la procédure d'annotation avec cet outil, nos choix d'annotation ainsi que le corpus produit, en s'intéressant en particulier à une comparaison avec le corpus équivalent FTB (French Treebank) développé pour l'écrit. Abstract. Constituency annotation of spontaneous speech for temporal analysis needs: results and comparison between spoken and written French. This paper presents the main results drawn from the syntactic part of Temporal@ODIL, a project whose objective is the construction of a temporally annotated corpus of spontaneous speech for French. We describe ODIL_Syntax, a freely distributed constituency treebank on which our temporal annotation is grounded. The syntactic annotation was performed on Contemplata, a Web-based annotation platform developed specifically for our project, which is also freely distributed and which integrates a syntactic parser, allowing a semi-automatic annotation. This paper gives a description of the annotation guidelines and the annotation procedure using Contemplata, as well as a statistical description of our corpus, compared with the French Treebank, the largest constituency-based resource for written French.

Alary muscles (AMs) have been described as a component of the cardiac system in various arthropods. Lineage-related thoracic muscles (TARMs), linking the exoskeleton to specific gut regions, have recently been discovered in