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Blood vessel formation is a fine-regulated process and interfering with blood vessel formation causes embryonic lethality as well as associated with many diseases in the adult, including inflammatory, ischemic, and cancer metastatic diseases. Brain contains abundant blood vessels and has some unique physiological functions, such as blood-brain barrier. Due to the thickness and opaque characters of the tissues, it is a challenge to visualize the three-dimensional structures of the brain blood vessels in the mouse. Therefore, establishing a protocol to display the three-dimensional structures in the brain is required for exploring the regulatory molecular mechanisms in brain blood vessel formation. In this manuscript, we introduced a whole-mount and a vibratome thick section of mouse embryonic hindbrain to display the three-dimensional structures of brain vascular system.

Neurons in nucleus gigantocellularis (NGC) have been shown by many lines of evidence to be important for regulating generalized CNS arousal. Our previous study on mouse pups suggested that the development of NGC neurons’ capability to fire action potential (AP) trains may both lead to the development of behavioral arousal and, itself, depend on an increase in delayed rectifier currents. Now, using whole-cell patch clamp, we studied delayed rectifier currents in two stages. First, we used primary cultured neurons isolated from E12.5 embryonic hindbrain (HB), a dissection which contains all of NGC, to take advantage of studying neurons in vitro in preference to using neurons in situ or in brain slices. HB neurons were tested with Guangxitoxin-1E and Resveratrol, two inhibitors of Kv2 channels which mediate the main bulk of delayed rectifier currents. Both inhibitors depressed delayed rectifier currents, but differentially: while Resveratrol reduced or abolished action potentials in AP trains, Guangxitoxin-1E did not. Since Resveratrol affects the Kv2.2 subtype, the development of the delayed rectifier mediated through Kv2.2 channels may lead to the development of HB neurons’ capability to generate AP trains. Stage Two in this work found that electrophysiological properties of the primary HB neurons that were recorded are essentially the same as those of NGC neurons. Thus, from the two stages combined, we propose that currents mediated through Kv2.2 are important for generating AP trains which, in turn, lead to the development of mouse pup behavioral arousal.

In the developing central nervous system, many neurons migrate tangentially, parallel to the pial surface and independently of radial glia processes. Tangential migration has been first described in the embryonic hindbrain where neurons of the precerebellar nuclei (PCN) and of the facial branchiomotor nucleus (FBM) follow complex migratory routes along the anterior–posterior and dorsoventral axis. We are reviewing here the cellular and molecular mechanisms which control the tangential migration of PCN and FBM neurons. To a large extent these models are based on the phenotypic analysis of multiple mouse and fish mutants. Although mounting evidence suggests that various diffusible molecules, such as slits and netrin1, influence the ventral migration of PCN neurons and their behavior at the midline, the mechanisms controlling their anterior–posterior distribution are still largely unknown. By contrast, the caudal migration of FBM neurons has been extensively studied and shown to be controlled by wnt, growth factors, and components of the PCP pathways, even though chemotropic attractive and repulsive molecules might also be involved. Interestingly, various secreted molecules such as CXCL12 and retinoic acid seem responsible of the preferential subpial position of both PCN and FBM migrating neurons. For the two types of neurons, the final switch from a tangential mode of migration to a radial one also seems to obey to some common rules.

The embryonic hindbrain is subdivided into a series of metameric units termed rhombomeres, which display features that strongly suggest they are autonomous developmental units. However, some aspects of their phenotype develop nonautonomously. Here we have analyzed the possibility that interrhombomere interactions generate the pattern of segmental neuronal differentiation. The differentiation of both projection interneurons and motor neurons in the hindbrain is retarded in rhombomeres 3 and 5. We demonstrate here that if either rhombomere 3 or 5 is isolated from the influence of their neighbours, either in vitro or in vivo, then these segments no longer display delayed neuronal diufferentiation. We further show that the retardation of motor neurons differentiation in rhombomeres 3 and 5 is, at least in part, mediated by Bmp-4. If this molecule is inhibited, by grafting cells expressing chordin, then the motor neurons of these rhombomeres develop ahead of their normal schedule.

Members of theAntennapediaclass of homeobox genes, known as Hox genes, are believed to be pivotal in vertebrate craniofacial development. Here we show that eight members of paralogous groups 1, 2, 3, and 4 are expressed in the human embryonic hindbrain and branchial arches at 4 weeks of development. The combinatorial patterns of expression of genes representing the first three paralogous groups parallel the patterns described for their homologues in various animal models, demonstrating a high degree of conservation of the branchial Hox code. Arch expression of group 4 genes is defined for the first time in any vertebrate. Furthermore, as development proceeds, individual paralogues of a single paralogous group (group 3), which initially share a common expression domain, are differentially down-regulated in a tissue-, organ-, or site-specific fashion.