Three‐dimensional morphology of inner ear development in <i>Xenopus laevis</i>

Bever, Michele Miller; Jean, Ying Y.; Fekete, Donna M.

doi:10.1002/dvdy.10316

Cited by 48 publications

(16 citation statements)

References 36 publications

(40 reference statements)

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“…Xenopus embryos were exposed to BPA (5 or 10 μM) from stage NF 18 to stage NF 40 (48 h) and examined at stage NF 45. The upper panel shows the morphology of the otoliths (or otoconia [73]) in control and BPA treated embryos. Note that 5 and 10 μM of BPA induce a progressive reduction in the size of the otoconia.…”

Section: Resultsmentioning

confidence: 99%

Bisphenol A induces otolith malformations during vertebrate embryogenesis

et al. 2011

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BackgroundThe plastic monomer and plasticizer bisphenol A (BPA), used for manufacturing polycarbonate plastic and epoxy resins, is produced at over 2.5 million metric tons per year. Concerns have been raised that BPA acts as an endocrine disruptor on both developmental and reproductive processes and a large body of evidence suggests that BPA interferes with estrogen and thyroid hormone signaling. Here, we investigated BPA effects during embryonic development using the zebrafish and Xenopus models.ResultsWe report that BPA exposure leads to severe malformations of the otic vesicle. In zebrafish and in Xenopus embryos, exposure to BPA during the first developmental day resulted in dose-dependent defects in otolith formation. Defects included aggregation, multiplication and occasionally failure to form otoliths. As no effects on otolith development were seen with exposure to micromolar concentrations of thyroid hormone, 17-ß-estradiol or of the estrogen receptor antagonist ICI 182,780 we conclude that the effects of BPA are independent of estrogen receptors or thyroid-hormone receptors. Na+/K+ ATPases are crucial for otolith formation in zebrafish. Pharmacological inhibition of the major Na+/K+ ATPase with ouabain can rescue the BPA-induced otolith phenotype.ConclusionsThe data suggest that the spectrum of BPA action is wider than previously expected and argue for a systematic survey of the developmental effects of this endocrine disruptor.

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Section: Resultsmentioning

confidence: 99%

Bisphenol A induces otolith malformations during vertebrate embryogenesis

et al. 2011

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“…This suggests that semicircular canals would be in fact capable of detecting naturally occurring angular accelerations during locomotor activity at much younger stages. It is therefore quite possible that semicircular canals become already functional for detecting self-motion immediately after structural completion at stage 46 (Haddon and Lewis, 1991; Bever et al, 2003; Quick and Serrano, 2005). Therefore, high stimulus acceleration magnitudes such as those generated during swimming could theoretically elicit an angular VOR.…”

Section: Behavioral Onset Of Vestibular Reflexesmentioning

confidence: 99%

“…While the utricular macula is already well developed at larval stage 42/43 (Nieuwkoop and Faber, 1994), semicircular canals appear initially as paired axial protrusions early after hatching (stage 43). During subsequent development these protrusions fuse and finally become morphologically complete at stage 46–47 (Haddon and Lewis, 1991) at ~5 days post-fertilization (Bever et al, 2003). A differential timing of semicircular canal and otolith organ formation has also been observed in salamanders (Wiederhold et al, 1995) and zebrafish (Haddon and Lewis, 1996; Bever and Fekete, 2002; Whitfield et al, 2002).…”

Section: Functional Organization Of Vestibular Circuitriesmentioning

confidence: 99%

Ontogenetic Development of Vestibulo-Ocular Reflexes in Amphibians

Branoner

Chagnaud

2016

Front. Neural Circuits

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Vestibulo-ocular reflexes (VOR) ensure gaze stability during locomotion and passively induced head/body movements. In precocial vertebrates such as amphibians, vestibular reflexes are required very early at the onset of locomotor activity. While the formation of inner ears and the assembly of sensory-motor pathways is largely completed soon after hatching, angular and translational/tilt VOR display differential functional onsets and mature with different time courses. Otolith-derived eye movements appear immediately after hatching, whereas the appearance and progressive amelioration of semicircular canal-evoked eye movements is delayed and dependent on the acquisition of sufficiently large semicircular canal diameters. Moreover, semicircular canal functionality is also required to tune the initially omnidirectional otolith-derived VOR. The tuning is due to a reinforcement of those vestibulo-ocular connections that are co-activated by semicircular canal and otolith inputs during natural head/body motion. This suggests that molecular mechanisms initially guide the basic ontogenetic wiring, whereas semicircular canal-dependent activity is required to establish the spatio-temporal specificity of the reflex. While a robust VOR is activated during passive head/body movements, locomotor efference copies provide the major source for compensatory eye movements during tail- and limb-based swimming of larval and adult frogs. The integration of active/passive motion-related signals for gaze stabilization occurs in central vestibular neurons that are arranged as segmentally iterated functional groups along rhombomere 1–8. However, at variance with the topographic maps of most other sensory systems, the sensory-motor transformation of motion-related signals occurs in segmentally specific neuronal groups defined by the extraocular motor output targets.

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“…Amphibians and other vertebrates share similar auditory and vestibular physiology, with their vestibular organs particularly well conserved in position, structure, and function [47]. However, a striking difference is the unusual calcium carbonate crystalline forms of amphibian otoconia.…”

Section: Discussionmentioning

confidence: 99%

Lineage-specific evolution of the vertebrate Otopetringene family revealed by comparative genomic analyses

et al. 2011

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BackgroundMutations in the Otopetrin 1 gene (Otop1) in mice and fish produce an unusual bilateral vestibular pathology that involves the absence of otoconia without hearing impairment. The encoded protein, Otop1, is the only functionally characterized member of the Otopetrin Domain Protein (ODP) family; the extended sequence and structural preservation of ODP proteins in metazoans suggest a conserved functional role. Here, we use the tools of sequence- and cytogenetic-based comparative genomics to study the Otop1 and the Otop2-Otop3 genes and to establish their genomic context in 25 vertebrates. We extend our evolutionary study to include the gene mutated in Usher syndrome (USH) subtype 1G (Ush1g), both because of the head-to-tail clustering of Ush1g with Otop2 and because Otop1 and Ush1g mutations result in inner ear phenotypes.ResultsWe established that OTOP1 is the boundary gene of an inversion polymorphism on human chromosome 4p16 that originated in the common human-chimpanzee lineage more than 6 million years ago. Other lineage-specific evolutionary events included a three-fold expansion of the Otop genes in Xenopus tropicalis and of Ush1g in teleostei fish. The tight physical linkage between Otop2 and Ush1g is conserved in all vertebrates. To further understand the functional organization of the Ushg1-Otop2 locus, we deduced a putative map of binding sites for CCCTC-binding factor (CTCF), a mammalian insulator transcription factor, from genome-wide chromatin immunoprecipitation-sequencing (ChIP-seq) data in mouse and human embryonic stem (ES) cells combined with detection of CTCF-binding motifs.ConclusionsThe results presented here clarify the evolutionary history of the vertebrate Otop and Ush1g families, and establish a framework for studying the possible interaction(s) of Ush1g and Otop in developmental pathways.

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Three‐dimensional morphology of inner ear development in Xenopus laevis

Cited by 48 publications

References 36 publications

Bisphenol A induces otolith malformations during vertebrate embryogenesis

Bisphenol A induces otolith malformations during vertebrate embryogenesis

Ontogenetic Development of Vestibulo-Ocular Reflexes in Amphibians

Lineage-specific evolution of the vertebrate Otopetringene family revealed by comparative genomic analyses

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