The WTX/AMER1 gene family: evolution, signature and function

<p>Abstract</p> <p>Background</p> <p><it>WTX </it>is a novel gene mutated in a proportion of Wilms' tumors and in patients suffering from sclerosing bone dysplasia. On the molecular level WTX has been shown to act as an antagonist of canonical <it>Wnt/β-catenin </it>signaling in fish and mammals thus linking it to an essential pathway involved in normal development and cancer formation. Interestingly, WTX seems to also localize to an intranuclear component called paraspeckles. In spite of the growing interest of molecular biologists in <it>WTX</it>, little is known about its paralogs and its phylogenetic history.</p> <p>Results</p> <p>Using the amino-acid sequence of <it>WTX/AMER1 </it>as a tool for the assignment of orthology and paralogy, we here identify two novel proteins, <it>AMER2 </it>and <it>AMER3</it>, as "<it>WTX</it>" related. This <it>Amer </it>gene family is present in all currently available vertebrate genome sequences, but not invertebrate genomes and is characterized by six conserved blocks of sequences. The phylogenetic analysis suggests that the <it>protoAmer </it>gene originated early in the vertebrate lineage and was then duplicated due to whole genome duplications (WGD) giving rise to the three different <it>Amer </it>genes.</p> <p>Conclusion</p> <p>Our study represents the first phylogenetic analysis of <it>Amer </it>genes and reveals a new vertebrate specific gene family that is likely to have played an important role in the evolution of this subphylum. Divergent and conserved molecular functions of <it>Wtx/Amer1</it>, <it>Amer2 </it>and <it>Amer3 </it>are discussed.</p

Glutathione produced by Rhizobium tropici is important to prevent early senescence in common bean nodules

In this paper, we examine the importance of glutathione in symbiosis, using a glutathione biosynthetic gshB mutant derived from Rhizobium tropici CIAT899, a common bean (Phaseolus vulgaris) endosymbiont. Plants infected with the mutant strain presented a delayed nodulation phenotype and a reduction in the dry weight of aerial part of plants, suggesting diminished nitrogen-fixation activity. In addition, bacterial gshB expression was assayed in wild-type infected nodules, during the different steps of nodulation, and found to increase in mature and early senescent nodules. Conspicuously, nodules induced by gshB mutant bacteria presented an early senescent pattern, which was associated with increased levels of superoxide accumulation. These results provide a direct evidence of the role of bacterial glutathione in protecting nodules from reactive oxygen species, which may determine nodule senescence.Instituto de Biotecnologia y Biologia Molecula

Glutathione produced by Rhizobium tropici is important to prevent early senescence in common bean nodules

In this paper, we examine the importance of glutathione in symbiosis, using a glutathione biosynthetic gshB mutant derived from Rhizobium tropici CIAT899, a common bean (Phaseolus vulgaris) endosymbiont. Plants infected with the mutant strain presented a delayed nodulation phenotype and a reduction in the dry weight of aerial part of plants, suggesting diminished nitrogen-fixation activity. In addition, bacterial gshB expression was assayed in wild-type infected nodules, during the different steps of nodulation, and found to increase in mature and early senescent nodules. Conspicuously, nodules induced by gshB mutant bacteria presented an early senescent pattern, which was associated with increased levels of superoxide accumulation. These results provide a direct evidence of the role of bacterial glutathione in protecting nodules from reactive oxygen species, which may determine nodule senescence.Instituto de Biotecnologia y Biologia Molecula

An interactive and intuitive visualisation method for X-ray computed tomography data of biological samples in 3D Portable Document Format

3D imaging approaches based on X-ray microcomputed tomography (microCT) have become increasingly accessible with advancements in methods, instruments and expertise. The synergy of material and life sciences has impacted biomedical research by proposing new tools for investigation. However, data sharing remains challenging as microCT files are usually in the range of gigabytes and require specific and expensive software for rendering and interpretation. Here, we provide an advanced method for visualisation and interpretation of microCT data with small file formats, readable on all operating systems, using freely available Portable Document Format (PDF) software. Our method is based on the conversion of volumetric data into interactive 3D PDF, allowing rotation, movement, magnification and setting modifications of objects, thus providing an intuitive approach to analyse structures in a 3D context. We describe the complete pipeline from data acquisition, data processing and compression, to 3D PDF formatting on an example of craniofacial anatomical morphology in the mouse embryo. Our procedure is widely applicable in biological research and can be used as a framework to analyse volumetric data from any research field relying on 3D rendering and CT-biomedical imaging

A distinct cardiopharyngeal mesoderm genetic hierarchy establishes antero-posterior patterning of esophagus striated muscle

In most vertebrates, the upper digestive tract is composed of muscularized jaws linked to the esophagus that permits food ingestion and swallowing. Masticatory and esophagus striated muscles (ESM) share a common cardiopharyngeal mesoderm (CPM) origin, however ESM are unusual among striated muscles as they are established in the absence of a primary skeletal muscle scaffold. Using mouse chimeras, we show that the transcription factors Tbx1 and Isl1 are required cell-autonomously for myogenic specification of ESM progenitors. Further, genetic loss-of-function and pharmacological studies point to MET/HGF signaling for antero-posterior migration of esophagus muscle progenitors, where Hgf ligand is expressed in adjacent smooth muscle cells. These observations highlight the functional relevance of a smooth and striated muscle progenitor dialogue for ESM patterning. Our findings establish a Tbx1-Isl1-Met genetic hierarchy that uniquely regulates esophagus myogenesis and identify distinct genetic signatures that can be used as framework to interpret pathologies arising within CPM derivatives.Peer reviewe

Local retinoic acid signaling directs emergence of the extraocular muscle functional unit

Coordinated development of muscles, tendons, and their attachment sites ensures emergence of functional musculoskeletal units that are adapted to diverse anatomical demands among different species. How these different tissues are patterned and functionally assembled during embryogenesis is poorly understood. Here, we investigated the morphogenesis of extraocular muscles (EOMs), an evolutionary conserved cranial muscle group that is crucial for the coordinated movement of the eyeballs and for visual acuity. By means of lineage analysis, we redefined the cellular origins of periocular connective tissues interacting with the EOMs, which do not arise exclusively from neural crest mesenchyme as previously thought. Using 3D imaging approaches, we established an integrative blueprint for the EOM functional unit. By doing so, we identified a developmental time window in which individual EOMs emerge from a unique muscle anlage and establish insertions in the sclera, which sets these muscles apart from classical muscle-to-bone type of insertions. Further, we demonstrate that the eyeballs are a source of diffusible all-trans retinoic acid (ATRA) that allow their targeting by the EOMs in a temporal and dose-dependent manner. Using genetically modified mice and inhibitor treatments, we find that endogenous local variations in the concentration of retinoids contribute to the establishment of tendon condensations and attachment sites that precede the initiation of muscle patterning. Collectively, our results highlight how global and site-specific programs are deployed for the assembly of muscle functional units with precise definition of muscle shapes and topographical wiring of their tendon attachments

Muscle Interstitial Cells: A Brief Field Guide to Non-satellite Cell Populations in Skeletal Muscle

Skeletal muscle regeneration is mainly enabled by a population of adult stem cells known as satellite cells. Satellite cells have been shown to be indispensable for adult skeletal muscle repair and regeneration. In the last two decades, other stem/progenitor cell populations resident in the skeletal muscle interstitium have been identified as "collaborators" of satellite cells during regeneration. They also appear to have a key role in replacing skeletal muscle with adipose, fibrous, or bone tissue in pathological conditions. Here, we review the role and known functions of these different interstitial skeletal muscle cell types and discuss their role in skeletal muscle tissue homeostasis, regeneration, and disease, including their therapeutic potential for cell transplantation protocols

Functional study ox WTX, a novel negative regulator of the WNT/beta-catenin pathway, during mouse embryonic development

The WNT/beta-catenin pathway plays a crucial role in embryonic development and adult tissue homeostasis. Deregulation of the pathway can induce devastating developmental defects and later on in life, disease and cancer. WTX/AMER1 is a novel negative regulator of the canonical WNT pathway that induces degradation of beta-catenin in the cytoplasm. Loss-of-function mutations in WTX cause two human developmental pathologies: Wilms tumor and an X-linked sclerosing bone dysplasia (OSCS). My thesis has aimed to study the function of Wtx in vivo by making use of the mouse as a model organism. First we have performed a phylogenetic study that identified two novel proteins, AMER2 and AMER3, as WTX related. In addition, we have performed an in-depth expression analysis of all Amer family members during mouse embryonic development. In order to elucidate the developmental role of Wtx, we have generated a mouse model carrying a conditional knock out allele of Wtx. We have shown that germline inactivation of Wtx results in male lethality and a variety of developmental abnormalities in the skeletal system, on both intramembranous and endochondral bones. In the sternum of Wtx mouse mutants, we have detected an aberrant fusion of the sternebrae leading to an almost completely bifid sterni. We have provided evidence for a genetic interaction between Wtx and beta-catenin during sternal fusion. These data, together with the similarities between our Wtx mouse model phenotype and the defects displayed by human OSCS patients carrying germline mutations in WTX, allow us to confirm an important role for Wtx in the control of beta-catenin stability in skeletal precursors during bone formation.La voie WNT/beta-caténine joue un rôle crucial dans le développement embryonnaire et l'homéostasie des tissus adultes. Sa dérégulation entraîne des malformations au cours du développement embryonnaire, elle est associée à la tumorigenèse. WTX/AMER1 est un nouveau régulateur négatif de la voie WNT canonique qui induit la dégradation de b-caténine dans le cytoplasme. Des mutations perte de fonction dans WTX ont été identifiées dans deux pathologies humaines du de veloppement: la tumeur de Wilms et la dysplasie osseuse sclérosante liée au chromosome X (OSCS). Cette thèse a eu pour objectif l étude de la fonction de Wtx in vivo en utilisant la souris comme modèle d études. Tout d abord, une étude phylogénétique nous a permis d identifier deux nouvelles protéines, AMER2 et AMER3, appartenant à la famille de WTX. Ensuite nous avons effectué une analyse approfondie du patron d expression de ces trois gènes au cours du développement embryonnaire de la souris. Enfin, nous avons généré un modèle de souris permettant l'inactivation conditionnelle de WTX. L invalidation de Wtx dans la lignée germinale (Wtx-KO) entraîne la mort des nouveau-nés mâles ainsi que des anomalies du squelette intramembraneux et endochondral. Nous avons détecté dans le sternum des souris Wtx-KO une fusion aberrante au niveau des sternèbres et montré l existence d'une interaction génétique entre Wtx et beta-caténine pendant le processus de fusion. Ainsi, l ensemble de ces données et les ressemblances des patients porteurs de mutations germinales dans WTX avec notre modèle murin nous ont permis de confirmer le rôle majeur de Wtx dans le contrôle de la stabilité de beta-caténine lors de la formation des os.NICE-BU Sciences (060882101) / SudocSudocFranceF

Interplay between Pitx2 and Pax7 temporally governs specification of extraocular muscle progenitors

Posted August 25, 2023 on bioRxiv.Gene regulatory networks that act upstream of skeletal muscle fate determinants are distinct in different anatomical locations. Despite recent efforts, a clear understanding of the cascade of events underlying the emergence and maintenance of the stem cell pool in specific muscle groups remains unresolved and debated. Here, we invalidated Pitx2 with multiple Cre -driver mice prenatally, postnatally, and during lineage progression and showed that this gene becomes progressively dispensable for specification and maintenance of the extraocular muscle (EOM) stem cell pool, yet it is the major EOM upstream regulator during early development. Moreover, constitutive inactivation of Pax7 postnatally showed a greater loss of muscle stem cells in the EOM compared to the limb, pointing to a relay between Pitx2 , Myf5 and Pax7 for maintenance of the EOM stem cells. Further, we demonstrate that EOM stem cells adopt a quiescent state earlier that those in limb muscles and do not spontaneously re-enter in proliferation in the adult as previously suggested, yet EOMs have a significantly higher content of Pax7+ muscle stem cells per area pre- and post-natally. This unique feature could result from different dynamics of lineage progression in vivo , given the lower fraction of committed and differentiating EOM myoblasts. Finally, significantly less MuSCs are present in EOM compared to the limb in the mdx mouse model for Duchenne muscular dystrophy. Overall, our study provides a comprehensive in vivo characterization of muscle stem cell heterogeneity along the body axis and brings further insights into the unusual sparing of EOM during muscular dystrophy

Variations in the Efficiency of Lineage Marking and Ablation Confound Distinctions between Myogenic Cell Populations

Comment in : Response: Contributions of the Myf5-independent lineage to myogenesis. [Dev Cell. 2014]International audienceThe myogenic regulatory genes Myf5, Mrf4, Myod, and Myogenin likely arose by gene duplications during evolution, presumably to address the more demanding requirements of the vertebrate body plan. Two cell lineages were proposed to be regulated independently by Myf5 and Myod to safeguard against tissue failure. Here we report severe muscle loss following ablation of Myf5-expressing cells. Using both lineage-specific and ubiquitous reporter alleles, we show that the remaining muscles in Myf5Cre-DTA embryos arise mainly from Myf5+ escaper cells. Elimination of Myf5Cre-DTA cells on a Myod null background did not result in the total absence of skeletal muscles, as would be expected if a Myod+/Myf5-independent cell population played a major role in this scenario. Therefore, these observations are incompatible with a previously proposed functional two-lineage model. These findings will have an impact on the interpretation of phenotypes obtained using similar strategies in other tissues