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Melanoma is a rare sporadic pediatric cancer caused byde novogenetic accidents. To analyze the involvement ofFBXO32of unknown biological significance, we set up original developmental invivo,ex vivo, andin vitromodels to unmask the biological role ofFBXO32in cephalic and trunk neural crest lineages. We show thatFBXO32silencing impairs melanocyte proliferation, differentiation, and vascularization. In rescue experiments, co-electroporation with the human wild-type gene compensates for the silencing of the endogenous gene and restores normal melanocyte phenotypes. By contrast, co-electroporation with the human variant,FBXO32G139S, alters melanocyte differentiation, pigment synthesis, triggers migration to the dermis, and favors angiotropism. Transcriptomic analysis reveals targets associated with melanocyte transformation, cytoskeleton remodeling, and focal adhesion. We show thatFBXO32orchestrates unexpected interactions withASIPfor melanogenesis andBAP1for the post-translational ubiquitination system. We proposeFBXO32as a tumor suppressor gene capable of preventing the onset of pediatric melanoma.

The neural crest, a unique cell population originating from the primitive neural field, has a multi-systemic and structural contribution to vertebrate development. At the cephalic level, the neural crest generates most of the skeletal tissues encasing the developing forebrain and provides the prosencephalon with functional vasculature and meninges. Over the last decade, we have demonstrated that the cephalic neural crest (CNC) exerts an autonomous and prominent control on forebrain and sense organs development. The present paper reviews the primary mechanisms by which CNC can orchestrate vertebrate encephalization. Demonstrating the role of the CNC as an exogenous source of patterning for the forebrain provides a novel conceptual framework with profound implications for understanding neurodevelopment. From a biomedical standpoint, these data suggest that the spectrum of neurocristopathies is broader than expected and that some neurological disorders may stem from CNC dysfunctions.

International audience; For decades, the quail-chick system has been a gold standard approach to track cells and their progenies over complex morphogenetic movements and long-range migrations as well as to unravel their dialogue and interplays in varied processes of cell induction. More specifically, this model became decisive for the systematic explorations of the neural crest and its lineages and allowed a tremendous stride in understanding the wealth and complexity of this fascinating cell population. Much of our knowledge on craniofacial morphogenesis and vertebrate organogenesis was first gained in avian chimeras and later extended to mammalian models and humans. In addition, this system permits tissue and gene manipulations to be performed at once in the same cell population. Through the use of in ovo electroporation, this model became tractable for functional genomics, hence being even more resourceful for functional studies. Due to the ease of access and the possibility to combine micromanipulation of tissue anlagen and gene expression, this model offers the prospect of decrypting instructive versus permissive tissue interactions, to identify and crack the molecular codes underlying cell positioning and differentiation, with an unparalleled spatiotemporal accuracy.

International audience

In order to better understand the mechanisms underlying the physiology of vision, it is a necessary prerequisite to know the embryological bases of eye development and associated tissues. Eye formation starts during the fourth week of human embryonic life, when the ocular primordium can be distinguished from the lateral diverticula of the anterior brain by complex morphogenetic movements. It requires the input of various germ layers of the embryo: neuroectoderm, surface ectoderm, mesoderm and neural crest cells, in order to elaborate the different components. Perturbations of the cellular interactions and molecular mechanisms mobilized during these critical steps are responsible for varied congenital anomalies. We will discuss, relative to this, the embryological processes where their misregulation are at the root of ocular malformations and which are developed in more detail in other chapters of this book., Comment: in French

National audience; In order to better understand the mechanisms underlying the physiology of vision, it is a necessary prerequisite to know the embryological bases of eye development and associated tissues. Eye formation starts during the fourth week of human embryonic life, when the ocular primordium can be distinguished from the lateral diverticula of the anterior brain by complex morphogenetic movements. It requires the input of various germ layers of the embryo: neuroectoderm, surface ectoderm, mesoderm and neural crest cells, in order to elaborate the different components. Perturbations of the cellular interactions and molecular mechanisms mobilized during these critical steps are responsible for varied congenital anomalies. We will discuss, relative to this, the embryological processes where their misregulation are at the root of ocular malformations and which are developed in more detail in other chapters of this book.; Afin d'appréhender les mécanismes qui sous-tendent la physiologie de la vision, la connaissance des bases embryologiques du développement de l’œil et de ses annexes est un prérequis indispensable. La morphogénèse oculaire débute au cours de la quatrième semaine de vie embryonnaire, alors que l'ébauche oculaire s'individualise des diverticules latéraux du cerveau antérieur par des mouvements morphogénétiques complexes. Elle sollicite la contribution respective des divers feuillets de l'embryon, le neurectoderme, l'ectoderme de surface, le mésoderme et les cellules de la crête neurale, pour l'élaboration de ses différentes composantes. Les perturbations des interactions cellulaires et des mécanismes moléculaires mobilisés au cours de ces étapes critiques sont responsables d'anomalies congénitales variées. Nous évoquerons, à cet égard, les processus embryologiques dont les dérégulations sont à l'origine des malformations oculaires et qui font, plus particulièrement, l'objet de chapitres détaillés dans cet ouvrage.

In order to better understand the mechanisms underlying the physiology of vision, it is a necessary prerequisite to know the embryological bases of eye development and associated tissues. Eye formation starts during the fourth week of human embryonic life, when the ocular primordium can be distinguished from the lateral diverticula of the anterior brain by complex morphogenetic movements. It requires the input of various germ layers of the embryo: neuroectoderm, surface ectoderm, mesoderm and neural crest cells, in order to elaborate the different components. Perturbations of the cellular interactions and molecular mechanisms mobilized during these critical steps are responsible for varied congenital anomalies. We will discuss, relative to this, the embryological processes where their misregulation are at the root of ocular malformations and which are developed in more detail in other chapters of this book., Afin d'appréhender les mécanismes qui sous-tendent la physiologie de la vision, la connaissance des bases embryologiques du développement de l’œil et de ses annexes est un prérequis indispensable. La morphogénèse oculaire débute au cours de la quatrième semaine de vie embryonnaire, alors que l'ébauche oculaire s'individualise des diverticules latéraux du cerveau antérieur par des mouvements morphogénétiques complexes. Elle sollicite la contribution respective des divers feuillets de l'embryon, le neurectoderme, l'ectoderme de surface, le mésoderme et les cellules de la crête neurale, pour l'élaboration de ses différentes composantes. Les perturbations des interactions cellulaires et des mécanismes moléculaires mobilisés au cours de ces étapes critiques sont responsables d'anomalies congénitales variées. Nous évoquerons, à cet égard, les processus embryologiques dont les dérégulations sont à l'origine des malformations oculaires et qui font, plus particulièrement, l'objet de chapitres détaillés dans cet ouvrage.

In order to better understand the mechanisms underlying the physiology of vision, it is a necessary prerequisite to know the embryological bases of eye development and associated tissues. Eye formation starts during the fourth week of human embryonic life, when the ocular primordium can be distinguished from the lateral diverticula of the anterior brain by complex morphogenetic movements. It requires the input of various germ layers of the embryo: neuroectoderm, surface ectoderm, mesoderm and neural crest cells, in order to elaborate the different components. Perturbations of the cellular interactions and molecular mechanisms mobilized during these critical steps are responsible for varied congenital anomalies. We will discuss, relative to this, the embryological processes where their misregulation are at the root of ocular malformations and which are developed in more detail in other chapters of this book., in French

Afin d’appréhender les mécanismes qui sous-tendent la physiologie de la vision, la connaissance des bases embryologiques du développement de l’œil et de ses annexes est un prérequis indispensable. La morphogénèse oculaire débute au cours de la quatrième semaine de vie embryonnaire, alors que l’ébauche oculaire s’individualise des diverticules latéraux du cerveau antérieur par des mouvements morphogénétiques complexes. Elle sollicite la contribution respective des divers feuillets de l’embryon, le neurectoderme, l’ectoderme de surface, le mésoderme et les cellules de la crête neurale, pour l’élaboration de ses différentes composantes. Les perturbations des interactions cellulaires et des mécanismes moléculaires mobilisés au cours de ces étapes critiques sont responsables d’anomalies congénitales variées. Nous évoquerons, à cet égard, les processus embryologiques dont les dérégulations sont à l’origine des malformations oculaires et qui font, plus particulièrement, l’objet de chapitres détaillés dans cet ouvrage.ISBN 978-2-294-75022-9

International audience; The neural crest (NC) is a remarkable structure of the Vertebrate embryo, which forms from the lateral borders of the neural plate (designated as neural folds) during neural tube closure. As soon as the NC is formed, its constitutive cells detach and migrate away from the neural primordium along definite pathways and at precise periods of time according to a rostro-caudal progression. The NC cells aggregate in definite places in the developing embryo, where they differentiate into a large variety of cell types including the neurons and glial cells of the peripheral nervous system, the pigment cells dispersed throughout the body and endocrine cells such as the adrenal medulla and the calcitonin producing cells. At the cephalic level only, in higher Vertebrates (but along the whole neural axis in Fishes and Amphibians), the NC is also at the origin of mesenchymal cells differentiating into connective tissue chondrogenic and osteogenic cells. Vertebrates belong to the larger group of Cordates which includes also the Protocordates (Cephalocordates and the Urocordates). All Cordates are characterized by the same body plan with a dorsal neural tube and a notochord which, in Vertebrates, exists only at embryonic stages. The main difference between Protocordates and Vertebrates is the very rudimentary development of cephalic structures in the former. As a result, the process of cephalization is one of the most obvious characteristics of Vertebrates. It was accompanied by the apparition of the NC which can therefore be considered as an innovation of Vertebrates during evolution. The application of a cell marking technique which consists in constructing chimeric embryos between two species of birds, the quail and the chicken, has led to show that the vertebrate head is mainly formed by cells originating from the NC, meaning that this structure was an important asset in Vertebrate evolution. Recent studies, described in this article, have strengthened this view by showing that the NC does not only provide the cells that build up the facial skeleton and most of the skull but plays a major role in early brain neurogenesis. It was shown that the cephalic NC cells produce signaling molecules able to regulate the activity of the two secondary organizing centers previously identified in the developing brain: the anterior neural ridge and the midbrain-hindbrain junction, which secrete Fgf8, a potent stimulator of early brain neurogenesis.

The effect of the application of pulsed electric fields to potato tissue on the diffusion of the fluorescent dye FM1-43 through the cell wall was studied. Potato tissue was subjected to field strengths ranging from 30 to 500 V/cm, with one 1 ms rectangular pulse, before application of FM1-43 and microscopic examination. Our results show a slower diffusion of FM1-43 in the electropulsed tissue when compared with that in the non-pulsed tissue, suggesting that the electric field decreased the cell wall permeability. This is a fast response that is already detected within 30 s after the delivery of the electric field. This response was mimicked by exogenous H2O2 and blocked by sodium azide, an inhibitor of the production of H2O2 by peroxidases.

Studies carried out in the avian embryo and based on the construction of quail-chick chimeras have shown that most of the skull and all the facial and visceral skeleton are derived from the cephalic neural crest (NC). Contribution of the mesoderm is limited to its occipital and (partly) to its otic domains. NC cells (NCCs) participating in membrane bones and cartilages of the vertebrate head arise from the diencephalon (posterior half only), the mesencephalon and the rhombencephalon. They can be divided into an anterior domain (extending down to r2 included) in which genes of the Hox clusters are not expressed (Hox-negative skeletogenic NC) and a posterior domain including r4 to r8 in which Hox genes of the four first paraloguous groups are expressed. The NCCs that form the facial skeleton belong exclusively to the anterior Hox-negative domain and develop from the first branchial arch (BA1). This rostral domain of the crest is designated as FSNC for facial skeletogenic neural crest. Rhombomere 3 (r3) participates modestly to both BA1 and BA2. Forced expression of Hox genes (Hoxa2, Hoxa3 and Hoxb4) in the neural fold of the anterior domain inhibits facial skeleton development. Similarly, surgical excision of these anterior Hox-negative NCCs results in the absence of facial skeleton, showing that Hox-positive NCCs cannot replace the Hox-negative domain for facial skeletogenesis. We also show that excision of the FSNC results in dramatic down-regulation of Fgf8 expression in the head, namely in ventral forebrain and in BA1 ectoderm. We have further demonstrated that exogenous FGF8 applied to the presumptive BA1 territory at the 5-6-somite stage (5-6ss) restores to a large extent facial skeleton development. The source of the cells responsible for this regeneration was shown to be r3, which is at the limit between the Hox-positive and Hox-negative domain. NCCs that respond to FGF8 by survival and proliferation are in turn necessary for the expression/maintenance of Fgf8 expression in the ectoderm. These results strongly support the emerging picture according to which the processes underlying morphogenesis of the craniofacial skeleton are regulated by epithelial-mesenchymal bidirectional crosstalk.

Afin d’appréhender les mécanismes qui sous-tendent la physiologie de la vision, la connaissance des bases embryologiques du développement de l’œil et de ses annexes est un prérequis indispensable. La morphogénèse oculaire débute au cours de la quatrième semaine de vie embryonnaire, alors que l’ébauche oculaire s’individualise des diverticules latéraux du cerveau antérieur par des mouvements morphogénétiques complexes. Elle sollicite la contribution respective des divers feuillets de l’embryon, le neurectoderme, l’ectoderme de surface, le mésoderme et les cellules de la crête neurale, pour l’élaboration de ses différentes composantes. Les perturbations des interactions cellulaires et des mécanismes moléculaires mobilisés au cours de ces étapes critiques sont responsables d’anomalies congénitales variées. Nous évoquerons, à cet égard, les processus embryologiques dont les dérégulations sont à l’origine des malformations oculaires et qui font, plus particulièrement, l’objet de chapitres détaillés dans cet ouvrage.ISBN 978-2-294-75022-9