Modern humans exhibit phenotypic traits and molecular events shared with other domesticates that are thought to be by-products of selection for reduced aggression. This is the human self-domestication hypothesis. As one of the first types of responses to a novel environment, epigenetic changes may have also facilitated early self-domestication in humans. Here, we argue that fish species, which have been recently domesticated, can provide model systems to study epigenetic drivers in human self-domestication. To test this, we used in silico approaches to compare genes with epigenetic changes in early domesticates of European sea bass with genes exhibiting methylation changes in anatomically modern humans (comparison 1), and neurodevelopmental cognitive disorders considered to exhibit abnormal self-domestication traits, i.e., schizophrenia, Williams syndrome, and autism spectrum disorders (comparison 2). Overlapping genes in comparison 1 were involved in processes like limb morphogenesis and phenotypes like abnormal jaw morphology and hypopigmentation. Overlapping genes in comparison 2 affected paralogue genes involved in processes such as neural crest differentiation and ectoderm differentiation. These findings pave the way for future studies using fish species as models to investigate epigenetic changes as drivers of human self-domestication and as triggers of cognitive disorders.

During vertebrate embryogenesis, tissues interact and influence each other\'s development to shape an embryo. While communication by molecular components has been extensively explored, the role of mechanical interaction between tissues during embryogenesis is just starting to be revealed. Addressing mechanical involvement in morphogenesis has traditionally been challenging mainly due to the lack of proper tools to measure and modify mechanical environments of cells in vivo. We have recently used atomic force microscopy (AFM) to show that the migration of the Xenopus laevis cephalic neural crest cells is triggered by stiffening of the mesoderm, a tissue that neural crest cells use as a migratory substrate in vivo. Interestingly we showed that the activity of the planar cell polarity (PCP) pathway is required to mediate this novel mechanical interaction between two tissues. In this chapter, we share the toolbox that we developed to study the role of PCP signaling in mesoderm cell accumulation and stiffening (in vivo) as well as the impact of mesoderm stiffness in promoting neural crest cell polarity and migration (ex vivo). We believe that these tools can be of general use for investigators interested in addressing the role of mechanical inputs in vivo and ex vivo.

The epithelial-mesenchymal transition (EMT) converts coherent epithelial structures into single cells. EMT is a dynamic cellular process that is not systematically completed (not all EMTs lead to single cells) and reversible (cells can re-epithelialize). EMT is orchestrated at multiple levels from transcription, to posttranslational modifications, to protein turnover. It involves remodeling of polarity and adhesion and enhances migratory capabilities. During physiological events such as embryogenesis or wound healing EMT is used to initiate cell migration, but EMT can also occur in pathological settings. In particular, EMT has been linked to fibrosis and cancer. Neural crest (NC) cells, an embryonic stem cell population whose behavior recapitulates the main steps of carcinoma progression, are a great model to study EMT. In this chapter, we provide a fully detailed protocol to extract NC cells from Xenopus embryos and culture them to study the dynamics of cell-cell adhesion, cell motility, and dispersion.

The study of cell migration has been greatly enhanced by the development of new model systems and analysis protocols to study this process in vivo. Zebrafish embryos have been a principal protagonist because they are easily accessible, genetically tractable, and optically transparent. Neural crest cells, on the other hand, are the ideal system to study cell migration. These cells migrate extensively, using different modalities of movement and sharing many traits with metastatic cancer cells. In this chapter, we present new tools and protocols that allow the study of NC development and migration in vivo.

Heart development is a complex process and begins with the long-range migration of cardiac progenitor cells during gastrulation. This culminates in the formation of a simple contractile tube with multiple layers, which undergoes remodeling into a four-chambered heart. During this morphogenesis, additional cell populations become incorporated. It is important to unravel the underlying genetic and cellular mechanisms to be able to identify the embryonic origin of diseases, including congenital malformations, which impair cardiac function and may affect life expectancy or quality. Owing to the evolutionary conservation of development, observations made in nonamniote and amniote vertebrate species allow us to extrapolate to human. This review will focus on the contributions made to a better understanding of heart development through studying avian embryos-mainly the chicken but also quail embryos. We will illustrate the classic and recent approaches used in the avian system, give an overview of the important discoveries made, and summarize the early stages of cardiac development up to the establishment of the four-chambered heart.

Over the past several decades there has been an increased availability of genetically modified mouse models used to mimic human pathologies. However, the ability to study cell movements and differentiation in vivo is still very difficult. Neurocristopathies, or disorders of the neural crest lineage, are particularly challenging to study due to a lack of accessibility of key embryonic stages and the difficulties in separating out the neural crest mesenchyme from adjacent mesodermal mesenchyme. Here, we set out to establish a well-defined, routine protocol for the culture of primary cranial neural crest cells. In our approach we dissect out the mouse neural plate border during the initial neural crest induction stage. The neural plate border region is explanted and cultured. The neural crest cells form in an epithelial sheet surrounding the neural plate border, and by 24 h after explant, begin to delaminate, undergoing an epithelial-mesenchymal transition (EMT) to become fully motile neural crest cells. Due to our two-dimensional culturing approach, the distinct tissue populations (neural plate versus premigratory and migratory neural crest) can be readily distinguished. Using live imaging approaches, we can then identify changes in neural crest induction, EMT and migratory behaviors. The combination of this technique with genetic mutants will be a very powerful approach for understanding normal and pathological neural crest cell biology.

The quail-chick chimera marking system, devised in 1969, gave a new impetus to the analysis of cell migrations and interactions in the developing nervous, immune and hematopoietic systems. The method is based on the observation that the constitutive heterochromatin in all embryonic and adult cells of the quail is condensed in one large mass in the centre of the nucleus and is associated with the nucleolus, making this organelle strongly stained with the Feulgen-Rossenbeck reaction. The association of cells or rudiments from two avian species, advocated as a means to identify cells that migrate during embryogenesis, was rapidly recognized in this context as a useful tool for the study of many developmental biology problems. This article summarizes the fundamental contribution of Nicole Le Douarin to the discovery and the application of this technique over the last 40 years.

Mammalian development occurs in utero, which makes it difficult to study the diverse morphogenetic events of neural crest cell development in vivo. Analyses of fixed samples in conjunction with histological methods to evaluate the spatiotemporal roles of specific genes of interest only provide snapshots of mammalian neural crest cell development. This chapter describes methods for isolating and culturing mouse embryos and their organs in vitro, outside the mother, to facilitate real-time imaging and functional analyses of the dynamics of neural crest cell development.

OBJECTIVE: When localised scleroderma occurs in the face, neck and scalp area, it is called scleroderma en coup de sabre (SCS) for its resemblance to the stroke of a sabre. Most observed characteristics: abnormal skin and dental development, facial atrophy and neurological complications. The aim was to evaluate the extent of SCS in the underlying subcutis, including teeth/bone tissues. The goal was to solve, how far the external visual skin abnormality extends in depth, and if the condition appears within and limited to craniofacial neural crest fields.
METHODS: Photographic and radiographic materials from six patients (one male, five females, aged 5-39 years) were included. The cases were divided in three groups, two in each, according to similarity in location of SCS in the skin. Dentition and gingiva were analysed clinically and from intra-oral photos, dental radiographs and orthopantomograms. Agenesis, dental maturity stage (root length), deviation in crown and root morphology (size and shape), and eruption disturbances were registered. Profile and frontal radiographs were analysed cephalometrically for jaw relationships and bone structures.
RESULTS: In SCS, skin affection corresponds to the neural crest regions/fields. A close spatial association between skin, teeth and bone affections within neural crest fields was found. No common traits in profile analyses were observed. Asymmetry from minor to severe appears in the frontal analyses. A malformation in planum sphenoidale was observed in two individuals with the same location of skin affections.
CONCLUSIONS: SCS conditions seem to extend from the skin in the depth to the sella turcica area within neural crest fields.

In the CNS, perivascular cells (\"pericytes\") associate with endothelial cells to mediate the formation of tight junctions essential to the function of the blood-brain barrier (BBB). The BBB protects the CNS by regulating the flow of nutrients and toxins into and out of the brain. BBB dysfunction has been implicated in the progression of Alzheimer\'s disease (AD), but the role of pericytes in BBB dysfunction in AD is not well understood. In the developing embryo, CNS pericytes originate from two sources: mesoderm and neural crest. In this study, we report two protocols using mesoderm or neural crest intermediates, to generate brain-specific pericyte-like cells from induced pluripotent stem cell (iPSC) lines created from healthy and AD patients. iPSC-derived pericytes display stable expression of pericyte surface markers and brain-specific genes and are functionally capable of increasing vascular tube formation and endothelial barrier properties.