Expression of sox3 is one of the earliest markers of fgfdependent otic epibranchial placode induction. Fgfsignalingdependent sox9a and atoh1a regulate otic. We propose that zebrafish otic neurogenesis and sensorigenesis require distinct fgfdependent gene networks fig. Ra and fgf signalling are required in the zebrafish otic vesicle to. In zebrafish and mouse, pax8 expression is the earliest known marker of otic induction, and pax2 homologs are expressed at slightly later stages of placodal development. The auditory plate becomes depressed and converted into the auditory pit or otic pit references. Zebrafish pax8 is required for otic placode induction and plays a redundant role with pax2 genes in the maintenance of the otic placode article in development 22. The vertebrate inner ear develops from initially simple ectodermal placode and vesicle stages into the complex. A neurogenic placode is an area of thickening of the epithelium in the embryonic head ectoderm layer that gives rise to neurons and other structures of the sensory nervous system placodes are embryonic structures that give rise to structures such as hair follicles, feathers and teeth. To address functions of sox2 and sox3, we generated knockouts and heat shockinducible transgenes. During the fourth week, the otic placode invaginates into the mesenchyme. It appears shortly after that of the eye, in the form of a patch of thickened ectoderm, the auditory plate, over the region of the hindbrain. The vertebrate inner ear forms a highly complex sensory structure responsible for the detection of sound and balance. Gene milesapart is required for formation of otic vesicle and hair.
Warga and kimmel 1990 briefly described stages of the blastula and gastrula. Lossoffunction experiments in zebrafish demonstrated that fgf3 and fgf8 are redundantly required at multiple stages of otic placode induction leger and brand, 2002. An earlier staging series for zebrafish, although less complete than the present one, fairly accurately por trays the first third or 1st day of embryonic develop ment, and includes useful sets of photographs hisaoka and battle, 1958. The auditory pit, also known as the otic pit, is the first rudiment of the internal ear. Multiple roles for fgf3 during cranial neural development in the chicken. Zebrafish embryos were incubated with su5402 or dmso control beginning at 10 hpf. In this study, we determined fgf3 expression in relation to otic development in the zebrafish and used antisense morpholino oligonucleotides to inhibit. Finally, wnt signaling also plays a role in otic placode patterning via regulation of pax gene expression mccarroll et al.
The images below show the first appearance on the embryo surface during week 4 and the eventual disappearance from the surface. Among them, gbx is especially important in the development of the otic placode 9. Analysis of compound mutants has not been reported. Mutant analysis, and lowlevel misexpression, showed that sox2 and sox3.
The neural tube has a longitudinal axis called the neuraxis, from the future brain area at the cranial end, to the conus medullaris of the spinal cord at the caudal end. The term neurogenic placode generally refers to cranial placodes that have neurogenic potential. Postembryonic development of the cranial lateral line canals and. Mutations disrupting formation of the prechordal plate and paraxial head mesoderm delay, but do not prevent otic placode induction in zebrafish mendonsa and riley, 1999. Grhl2 deficiency impairs otic development and hearing ability in a zebrafish model of the progressive dominant hearing loss dfna28 article pdf available in. Formation of the otic vesicle has been studied extensively in developmental model organisms including chicken, xenopus, zebrafish, axolotl, and mouse. The functional redundancy exhibited by fgf3 and fgf10 in early otic development is not a simple matter of coexpression of the two fgf genes in the same inducing tissue, as their expression patterns change dynamically during otic placode induction and only coincide for a brief time in the hindbrain, after the placode has begun to invaginate. In a study investigating the conditions that influence the response to fgf during otic placode induction, signaling of this factor has been shown to induce the expression of zebrafish otic genes such as pax8, pax2a, fgf24, and sox3 throughout the preplacodal region, which is important in setting the pattern of the otic vesicle. Fgf3 and fgf10a work in concert to promote maturation of the epibranchial placodes in zebrafish matthew n. Please use this form to recommend updates to the information in zfin.
Mesodermal fgf10b cooperates with other fgfs during. Fgf3 and fgf8 are required together for formation of the. Fgf signaling is required for eb placode induction. In contrast to the mammalian placode which invaginates as a single spherical layer of cells, the zebra fish lens placode quickly becomes a multilayered cell mass fig. It can be recognized in the mouse by expresson of neurogenin1 ngn1, a gene required for specification of neuroblasts of the otic placode as well as several other neurogenic placodes in the head. During development of the zebrafish inner ear, regional patterning in the. In embryology, the otic placode is a thickening of the ectoderm on the outer surface of a developing embryo from which the ear develops. Pdf specification of epibranchial placodes in zebrafish. The transition from the otic placode to the otic vesicle occurs during the 19th somite stage in zebrafish, xenopus, and chick. Fgf3 or fgf8 is sufficient to induce foxi1 positive eb pr ecursors and phox2b positive eb neurons in. In zebrafish the otic placode cavitates to form the otic vesicle also known as the otocyst, an epithelial structure with sharply defined borders. Placode article about placode by the free dictionary.
Specification of epibranchial placodes in zebrafish. Here, we identify a mutation in zebrafish, hearsay, which disrupts the initiation of placode formation. The formation of the otic placode is a complex process requiring multiple inductive signals. Sox10dependent neural crest origin of olfactory microvillous. For example, in zebrafish grafting hindbrain tissue on the ventral side of an embryo induces ectopic otic vesicles woo and fraser, 1998. Although inductive signals for otic placode formation have been characterized, less is known about the molecules that respond to these signals within otic primordia. Sensory hair cells 1 are generated prior to the formation of neuroblasts 2. We will contact you to arrange shipments when normal operations are resumed. All neurogenic placodes in zebrafish, including the olfactory placode, express the proneural bhlh transcription factor ngn1, which is known to be. Vertebrate pax2 and pax8 proteins are closely related transcription factors hypothesized to regulate early aspects of inner ear development. Zebrafish foxi1 mediates otic placode formation and jaw.
Fgf3 has long been implicated in otic placode induction and early development of the otocyst. Over the course of 12 days in the mouse, the otic placode dips into the mesenchyme, forming a cup. Otic vesicle formation occurs later, during the 2530 somite stage in mice. Fgf8 and fgf3 are required for zebrafish ear placode induction, maintenance.
The otic placode in zebrafish, on the other hand, occurs by cavitation. To address functions of sox2 and sox3 in otic and epibranchial development, we generated knockouts and heat shockinducible transgenes in zebrafish. Zebrafish pax8 is required for otic placode induction and. During the fourth week, the otic placode invaginates into the mesenchyme adjacent to the rhombencephalon to form the. Epibranchial ganglia, marked by expression of phox2a 25, were highly disorganized in itga5 morphants, though it is unclear whether the amount of epibranchial tissue was altered compare fig. Mutational analysis of tissuetissue interaction required. In wildtype embryos, the otic placode develops into the otic vesicle with the formation of neuronal precursorsneuroblasts purple and sensory hair cells light red in a stereotypical temporal order. Zebrafish inner ear development and function sciencedirect. A prominent feature of our research is to investigate how cellcell signaling and downstream geneinteractions control development. Zebrafish pax8 is required for otic placode induction and plays a redundant role with pax2 genes in the maintenance of the otic placode. Celltype heterogeneity in the early zebrafish olfactory epithelium is. By the fourth week in the human embryo, at its cranial end, three swellings have formed as.
One project in the lab focuses on how cell signaling regulates ectodermal patterning during gastrulation to establish the otic placode. About these antibodies all antibodies listed on this page were generated by researchers at the institute of neuroscience, university of oregon liu et al. We suggest a model of zebrafish inner ear development with several. Mayordomo r, rodriguezgallardo l, alvarez is 1998 morphological and quantitative studies in the otic region of the neural tube in chick embryos suggest a neuroectodermal origin for the otic placode. In chick, invagination of the otic placode occurs passively due to the movements of the surrounding placode.
Fish do not have a counterpart of the cochlea, the specialised auditory organ of amniotes, with its associated sensory. All orders will be processed in the order received. Fgf8 and fgf3 are required for zebrafish ear placode induction. Fgf3 and fgf10 are required for mouse otic placode.
Induction and segregation of the cranial placodes at the end of gastrulation, the ectoderm of the vertebrate embryo can be divided into three major domains. This article incorporates text in the public domain from. The 5th edition is available in print and within the zfin protocol wiki. A guide for the laboratory use of zebrafish danio rerio. The nonneural ectoderm and neural plate will develop into epidermis and central nervous system, respectively, while the neural plate border contains at least two cell populations.
Due to the covid19 pandemic, resource distribution has been suspended and services may be delayed. The ear, including both the vestibular system and the auditory system, develops from the otic placode beginning the third week of development. In zebrafish, fgf signaling participates in otic neurogenesis vemaraju et al. To analyze the role of fgf signaling in eb placode induction, we examined foxi1, pax2a, and phox2b expression in zebrafish embryos treated with a fgf receptor fgfr inhibitor, su5402 mohammadi et al. Whereas eb placodes are induced in the absence of fgf3 and fgf10a, they fail to express placode specific markers pax2a and sox3. We appreciate as much detail as possible and references as appropriate. We report here that sox2 is also expressed in the early otic epibranchial placode. The otic placode is a transient embryonic structure that gives rise to the inner ear. The roles of sox2 and sox3 during otic and epibranchial. Here, increasing wnt activity at early somite stages causes pax2a upregulation and an enhanced recruitment of cells into otic placode, and blocking wnt signaling has the opposite effect. Otic placode cells then assemble into an epithelium, which cavitates to form the otic vesicle. Monoclonal antibodies that recognize a variety of structures in zebrafish embryos are available from the library at the zebrafish international resource center.
Zirc estscdnas search zirc estscdnas for anything gene symbol abbreviation gene name estcdna name anatomy structure containing starting with ending with exactly matching matching case insensitive. Patterning, morphogenesis, and neurogenesis of zebrafish. Some new aspects on the evolutionary and developmental origin of the inner ear are summarised here. Foxi1 is necessary during otic placode induction and at that point foxi1 expression is independent of fgf signals nissen et al.
The auditory hearing and vestibular balance organ of the fish, equivalent to the inner ear of amniotes fish do not have an outer or middle ear. Schematic of the events during early otic development in zebrafish. Mutational analysis of tissuetissue interaction required for otic placode induction in zebrafish. This placode will differentiate to contribute almost entirely the components of the inner ear. In zebrafish, fgf3 and fgf8, dlx3b and dlx4b, and foxi1 have been identified as the earliest. Differences in cell morphology suggested that cellular differentiation occurred in the next few hours prior to separation of the lens mass from the cornea greiling and clark, 2009. We report here that sox2 is also expressed in the early otic epibranchial placode in zebrafish. However, the otic placode appeared smaller than normal by 14 hpf, and the otic vesicle was similarly reduced in size at 24 hpf compare fig.
The otic placode is a thickened ectodermal patch located adjacent to the dorsolateral hindbrain and above the branchial arches. Otic placode article about otic placode by the free. Several neuronal subtypes found in the early zebrafish olfactory placode are not derived from the neural crest, as previously thought, but from. Mesodermal fgf10b cooperates with other fgfs during induction of otic and epibranchial placodes in zebrafish.
At the end of gastrulation, the ectoderm of the vertebrate embryo can be divided into three major domains. Genetic interactions underlying otic placode induction and. We found that sox2 is also expressed in the early placode. Develops from a cranial ectodermal thickening, the otic placode, which arises on either side of the head midway between the eye and the first somite. Initial specification of the epibranchial placode in. The rim of the otic cup constricts, eventually pinching off from the overlying ectoderm to release the otic vesicle into the tissue below. Abstract in vertebrates, cranial sensory ganglia are mainly derived from ectodermal placodes, which are focal thickenings at characteristic positions in. In this study, we demonstrate that the zebrafish gene milesapart. The otic placode is the first of the sensory placodes visible on the surface of the developing human embryo.
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