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AJNR. American Journal of Neuroradiology Jan 2004We describe an infant in whom partial rhombencephalosynapsis was diagnosed by using MR imaging. The anterior vermis and nodulus were normally developed, but part of the...
We describe an infant in whom partial rhombencephalosynapsis was diagnosed by using MR imaging. The anterior vermis and nodulus were normally developed, but part of the posterior vermis was deficient. There was partial fusion of the hemispheres in the inferior part of the cerebellum. Partial rhombencephalosynapsis is described for the first time, and our findings support the recent embryologic observations.
Topics: Abnormalities, Multiple; Cerebellar Diseases; Cerebellum; Chromosome Pairing; Humans; Infant, Newborn; Magnetic Resonance Imaging; Male; Radiography; Rhombencephalon
PubMed: 14729524
DOI: No ID Found -
The Journal of Comparative Neurology May 2021In vertebrate animals, motor and sensory efferent neurons carry information from the central nervous system (CNS) to peripheral targets. These two types of efferent...
In vertebrate animals, motor and sensory efferent neurons carry information from the central nervous system (CNS) to peripheral targets. These two types of efferent systems sometimes bear a close resemblance, sharing common segmental organization, axon pathways, and chemical messengers. Here, we focus on the development of the octavolateral efferent neurons (OENs) and their interactions with the closely-related facial branchiomotor neurons (FBMNs) in zebrafish. Using live-imaging approaches, we investigate the birth, migration, and projection patterns of OENs. We find that OENs are born in two distinct groups: a group of rostral efferent neurons (RENs) that arises in the fourth segment, or rhombomere (r4), of the hindbrain and a group of caudal efferent neurons (CENs) that arises in r5. Both RENs and CENs then migrate posteriorly through the hindbrain between 18 and 48 hrs postfertilization, alongside the r4-derived FBMNs. Like the FBMNs, migration of the r4-derived RENs depends on function of the segmental identity gene hoxb1a; unlike the FBMNs, however, both OEN populations move independently of prickle1b. Further, we investigate whether the previously described "pioneer" neuron that leads FBMN migration through the hindbrain is an r4-derived FBMN/REN or an r5-derived CEN. Our experiments verify that the pioneer is an r4-derived neuron and reaffirm its role in leading FBMN migration across the r4/5 border. In contrast, the r5-derived CENs migrate independently of the pioneer. Together, these results indicate that the mechanisms OENs use to navigate the hindbrain differ significantly from those employed by FBMNs.
Topics: Animals; Cell Movement; Neurogenesis; Neurons, Efferent; Rhombencephalon; Zebrafish
PubMed: 32869305
DOI: 10.1002/cne.25021 -
Journal of Neurochemistry Jun 2007Development of the central nervous system is coordinated by intercellular signalling centres established within the neural tube. The isthmic organizer (IsO), located... (Review)
Review
Development of the central nervous system is coordinated by intercellular signalling centres established within the neural tube. The isthmic organizer (IsO), located between the midbrain and anterior hindbrain, is one such centre. Important signal molecules secreted by the IsO include members of the fibroblast growth factor and Wnt families. These signals are integrated with dorsally and ventrally derived signals to regulate development of the midbrain and rhombomere 1 of the hindbrain. The IsO is operational for a remarkably long period of time. Depending on the developmental stage, it controls a variety of processes such as cell survival, cell identity, neural precursor proliferation, neuronal differentiation and axon guidance. This review focuses on the fibroblast growth factor signalling, its novel molecular regulatory mechanisms and how this pathway regulates multiple aspects of cell behaviour in the developing midbrain and anterior hindbrain.
Topics: Animals; Critical Period, Psychological; Fibroblast Growth Factors; Gene Expression Regulation, Developmental; Mesencephalon; Rhombencephalon; Signal Transduction
PubMed: 17326764
DOI: 10.1111/j.1471-4159.2007.04463.x -
Journal of Anatomy Nov 2020Neuroanatomical reconstructions of extinct animals have long been recognized as powerful proxies for palaeoecology, yet our understanding of the endocranial anatomy of... (Comparative Study)
Comparative Study
Neuroanatomical reconstructions of extinct animals have long been recognized as powerful proxies for palaeoecology, yet our understanding of the endocranial anatomy of dromaeosaur theropod dinosaurs is still incomplete. Here, we used X-ray computed microtomography (µCT) to reconstruct and describe the endocranial anatomy, including the endosseous labyrinth of the inner ear, of the small-bodied dromaeosaur, Velociraptor mongoliensis. The anatomy of the cranial endocast and ear were compared with non-avian theropods, modern birds, and other extant archosaurs to establish trends in agility, balance, and hearing thresholds in order to reconstruct the trophic ecology of the taxon. Our results indicate that V. mongoliensis could detect a wide and high range of sound frequencies (2,368-3,965 Hz), was agile, and could likely track prey items with ease. When viewed in conjunction with fossils that suggest scavenging-like behaviours in V. mongoliensis, a complex trophic ecology that mirrors modern predators becomes apparent. These data suggest that V. mongoliensis was an active predator that would likely scavenge depending on the age and health of the individual or during prolonged climatic events such as droughts.
Topics: Animals; Dinosaurs; Ear, Inner; Fossils; Perception; Predatory Behavior; Rhombencephalon
PubMed: 32648601
DOI: 10.1111/joa.13253 -
Developmental Biology Jun 2002The Hoxa2 and Hoxb2 genes are members of paralogy group II and display segmental patterns of expression in the developing vertebrate hindbrain and cranial neural crest... (Review)
Review
Conservation and diversity in the cis-regulatory networks that integrate information controlling expression of Hoxa2 in hindbrain and cranial neural crest cells in vertebrates.
The Hoxa2 and Hoxb2 genes are members of paralogy group II and display segmental patterns of expression in the developing vertebrate hindbrain and cranial neural crest cells. Functional analyses have demonstrated that these genes play critical roles in regulating morphogenetic pathways that direct the regional identity and anteroposterior character of hindbrain rhombomeres and neural crest-derived structures. Transgenic regulatory studies have also begun to characterize enhancers and cis-elements for those mouse and chicken genes that direct restricted patterns of expression in the hindbrain and neural crest. In light of the conserved role of Hoxa2 in neural crest patterning in vertebrates and the similarities between paralogs, it is important to understand the extent to which common regulatory networks and elements have been preserved between species and between paralogs. To investigate this problem, we have cloned and sequenced the intergenic region between Hoxa2 and Hoxa3 in the chick HoxA complex and used it for making comparative analyses with the respective human, mouse, and horn shark regions. We have also used transgenic assays in mouse and chick embryos to test the functional activity of Hoxa2 enhancers in heterologous species. Our analysis reveals that three of the critical individual components of the Hoxa2 enhancer region from mouse necessary for hindbrain expression (Krox20, BoxA, and TCT motifs) have been partially conserved. However, their number and organization are highly varied for the same gene in different species and between paralogs within a species. Other essential mouse elements appear to have diverged or are absent in chick and shark. We find the mouse r3/r5 enhancer fails to work in chick embryos and the chick enhancer works poorly in mice. This implies that new motifs have been recruited or utilized to mediate restricted activity of the enhancer in other species. With respect to neural crest regulation, cis-components are embedded among the hindbrain control elements and are highly diverged between species. Hence, there has been no widespread conservation of sequence identity over the entire enhancer domain from shark to humans, despite the common function of these genes in head patterning. This provides insight into how apparently equivalent regulatory regions from the same gene in different species have evolved different components to potentiate their activity in combination with a selection of core components.
Topics: Animals; Base Sequence; Chick Embryo; DNA; Gene Expression Regulation, Developmental; Genes, Regulator; Homeodomain Proteins; Humans; Mice; Molecular Sequence Data; Neural Crest; Rhombencephalon; Sequence Homology, Nucleic Acid
PubMed: 12027433
DOI: 10.1006/dbio.2002.0665 -
Cell Sep 2020Hunger and thirst have distinct goals but control similar ingestive behaviors, and little is known about neural processes that are shared between these behavioral...
Hunger and thirst have distinct goals but control similar ingestive behaviors, and little is known about neural processes that are shared between these behavioral states. We identify glutamatergic neurons in the peri-locus coeruleus (periLC neurons) as a polysynaptic convergence node from separate energy-sensitive and hydration-sensitive cell populations. We develop methods for stable hindbrain calcium imaging in free-moving mice, which show that periLC neurons are tuned to ingestive behaviors and respond similarly to food or water consumption. PeriLC neurons are scalably inhibited by palatability and homeostatic need during consumption. Inhibition of periLC neurons is rewarding and increases consumption by enhancing palatability and prolonging ingestion duration. These properties comprise a double-negative feedback relationship that sustains food or water consumption without affecting food- or water-seeking. PeriLC neurons are a hub between hunger and thirst that specifically controls motivation for food and water ingestion, which is a factor that contributes to hedonic overeating and obesity.
Topics: Animals; Appetite; Appetite Regulation; Behavior Rating Scale; Drinking; Eating; Feedback; Feeding Behavior; Female; Glutamine; Homeostasis; Hunger; Locus Coeruleus; Male; Mice; Mice, Knockout; Motivation; Nerve Net; Neurons; Recombinant Proteins; Reward; Rhombencephalon; Single-Cell Analysis; Taste; Thirst
PubMed: 32841600
DOI: 10.1016/j.cell.2020.07.031 -
The International Journal of... 2007The inner ear, the sensory organ responsible for hearing and balance, contains specialized sensory and non-sensory epithelia arranged in a highly complex... (Comparative Study)
Comparative Study Review
The inner ear, the sensory organ responsible for hearing and balance, contains specialized sensory and non-sensory epithelia arranged in a highly complex three-dimensional structure. To achieve this level of complexity, a tight coordination between morphogenesis and cell fate specification is essential during otic development. Tissues surrounding the otic primordium and more particularly the adjacent segmented hindbrain, have been implicated in conferring signals required for inner ear development. In this review, we present the current view on the role of hindbrain signals in axial specification of the inner ear. The functional analysis of mutants of hindbrain segmentation genes, as well as the investigation of signaling pathways potentially involved, all point to an essential role of FGF, Wnt and Hh signaling in otic regionalization. However, these data provide conflicting evidence regarding the involvement of hindbrain signals in otic regionalization in fish and in amniotes. We discuss the possible origin of these differences.
Topics: Animals; Body Patterning; Ear, Inner; Embryo, Mammalian; Embryo, Nonmammalian; Fibroblast Growth Factors; Models, Biological; Morphogenesis; Rhombencephalon; Signal Transduction; Wnt Proteins
PubMed: 17891712
DOI: 10.1387/ijdb.072345ss -
Mechanisms of Development Sep 2004For the comparative embryologists of the early 20th century, the segment-like bulges that appear transiently during the early stages of vertebrate hindbrain development... (Review)
Review
For the comparative embryologists of the early 20th century, the segment-like bulges that appear transiently during the early stages of vertebrate hindbrain development were both the object of fascination and the subject of vigorous dispute. Conflicting views were held as to the significance of these 'rhombomeres' to brain development and their more general relevance to head evolution. Whether rhombomeres are inconsequential bumps in the embryonic brain or true segments-iterative or metameric units-has only recently been resolved. A number of studies using more modern techniques (such as immunohistochemistry, in situ hybridisation, axonal tracing, single cell labelling, heterotopic and orthotopic grafting, and the manipulation of gene expression by electroporation) have shown that the hindbrain has a truly metameric cellular organisation. The avian embryo has played a particularly prominent role in such studies by virtue of its large size and accessibility, its amenability to microsurgery, and its well-described anatomy. Furthermore, electrophysiological studies, also on avian embryos, have shown that segmentation of the parent neuroepithelium into rhombomeres plays a crucial part in establishing the functional organization of the hindbrain. Segmentation suggests the early allocation of defined sets of precursor cells and is therefore presumed to allow a specific identity for each successive segment to emerge from a common ground plan. This short review will focus on the contribution the avian embryo has made to our understanding of this fly-like region of the vertebrate brain, in respect of its morphology and neuronal architecture, the cellular and molecular mechanisms involved in establishing and maintaining the segments, and the molecular controls of segmental identity.
Topics: Animals; Body Patterning; Chick Embryo; Gene Expression Regulation, Developmental; Genes, Homeobox; Neurons; Retinoids; Rhombencephalon
PubMed: 15296973
DOI: 10.1016/j.mod.2004.04.018 -
Brain, Behavior and Evolution 2012It is widely held that three primary brain vesicles (forebrain, midbrain, and hindbrain vesicles) develop into five secondary brain vesicles in all vertebrates (von... (Comparative Study)
Comparative Study Review
It is widely held that three primary brain vesicles (forebrain, midbrain, and hindbrain vesicles) develop into five secondary brain vesicles in all vertebrates (von Baer's scheme). We reviewed previous studies in various vertebrates to see if this currently accepted scheme of brain morphogenesis is a rule applicable to vertebrates in general. Classical morphological studies on lamprey, shark, zebrafish, frog, chick, Chinese hamster, and human embryos provide only partial evidence to support the existence of von Baer's primary vesicles at early stages. Rather, they suggest that early brain morphogenesis is diverse among vertebrates. Gene expression and fate map studies on medaka, chick, and mouse embryos show that the fates of initial brain vesicles do not accord with von Baer's scheme, at least in medaka and chick brains. The currently accepted von Baer's scheme of brain morphogenesis, therefore, is not a universal rule throughout vertebrates. We propose here a developmental hourglass model as an alternative general rule: Brain morphogenesis is highly conserved at the five-brain vesicle stage but diverges more extensively at earlier and later stages. This hypothesis does not preclude the existence of deep similarities in molecular prepatterns at early stages.
Topics: Animals; Biological Evolution; Humans; Mesencephalon; Prosencephalon; Rhombencephalon; Vertebrates
PubMed: 22237006
DOI: 10.1159/000334842 -
Journal of Neurology, Neurosurgery, and... Jun 2002
Topics: Adult; Arnold-Chiari Malformation; Cerebellum; Female; Headache; Humans; Hydrocephalus; Magnetic Resonance Imaging; Prognosis; Rhombencephalon
PubMed: 12122202
DOI: 10.1136/jnnp.72.suppl_2.ii38