Molecular Genetics of Vestibular Organ Development

Chang, Weise; Cole, Laura K.; Cantos, Raquel; Wu, Doris K.

doi:10.1007/0-387-21567-0_2

Cited by 15 publications

(30 citation statements)

References 194 publications

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“…Indeed, lack of morphogenetic segregation in lamprey was recently attributed to the absence of Otx1 (Hammond and Whitfield, 2006) as previously suggested . Data on Otx1 mutants as well as others (see below) suggest that segregation and morphogenesis are linked, but the molecular basis of this link is not completely clear (Chang et al, 2004a, Chang et al, 2004b, Fritzsch et al, 2006b, Fritzsch and Wake, 1988. More genes that function like Otx genes are needed to fully understand what drives sensory epithelial segregation; in particular the segregation of canal cristae from gravistatic organs.…”

Section: Evolution Of the Vertebrate Ear Through Segregation Of Epithmentioning

confidence: 97%

“…FGF10 is known to interact with BMP4, which appears in the early development of the Drosophila mechanosensors and is part of the upstream regulation of cell fate determination. In the mammalian inner ear, Fgf10 and Bmp4 are both expressed in the presumptive sensory epithelia and they interact during canal morphogenesis (Chang et al, 2004b). Further, Bmp4 has been shown to reduce the size of prosensory patches, while Noggin, a BMP-inhibitor, increases the prosensory domain, thereby increasing the area of Fgf10 expression (Pujades et al, 2006).…”

Section: Evolution Of the Vertebrate Ear Through Segregation Of Epithmentioning

confidence: 99%

See 1 more Smart Citation

Molecular evolution of the vertebrate mechanosensory cell and ear

Fritzsch¹,

Beisel²,

Pauley³

et al. 2007

Int. J. Dev. Biol.

101

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The molecular basis of mechanosensation, mechanosensory cell development and mechanosensory organ development is reviewed with an emphasis on its evolution. In contrast to eye evolution and development, which apparently modified a genetic program through intercalation of genes between the master control genes on the top (Pax6, Eya1, Six1) of the hierarchy and the structural genes (rhodopsin) at the bottom, the as yet molecularly unknown mechanosensory channel precludes such a firm conclusion for mechanosensors. However, recent years have seen the identification of several structural genes which are involved in mechanosensory tethering and several transcription factors controlling mechanosensory cell and organ development; these warrant the interpretation of available data in very much the same fashion as for eye evolution: molecular homology combined with potential morphological parallelism. This assertion of molecular homology is strongly supported by recent findings of a highly conserved set of microRNAs that appear to be associated with mechanosensory cell development across phyla. The conservation of transcription factors and their regulators fits very well to the known or presumed mechanosensory specializations which can be mostly grouped as variations of a common cellular theme. Given the widespread distribution of the molecular ability to form mechanosensory cells, it comes as no surprise that structurally different mechanosensory organs evolved in different phyla, presenting a variation of a common theme specified by a conserved set of transcription factors in their cellular development. Within vertebrates and arthropods, some mechanosensory organs evolved into auditory organs, greatly increasing sensitivity to sound through modifications of accessory structures to direct sound to the specific sensory epithelia. However, while great attention has been paid to the evolution of these accessory structures in vertebrate fossils, comparatively less attention has been spent on the evolution of the inner ear and the central auditory system. Recent advances in our molecular understanding of ear and brain development provide novel avenues to this neglected aspect of auditory neurosensoy evolution.

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Section: Evolution Of the Vertebrate Ear Through Segregation Of Epithmentioning

confidence: 97%

Section: Evolution Of the Vertebrate Ear Through Segregation Of Epithmentioning

confidence: 99%

Molecular evolution of the vertebrate mechanosensory cell and ear

Fritzsch¹,

Beisel²,

Pauley³

et al. 2007

Int. J. Dev. Biol.

101

View full text Add to dashboard Cite

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“…The semicircular canals emerge initially as two epithelial protrusions or canal plates. The anterior and posterior semicircular canals are generated from the vertical canal plate, whereas the lateral semicircular canal develops from the horizontal canal plate (Martin and Swanson 1993;Chang et al 2004a). With the fusion of the opposing walls of the epithelial plates and resorption of the central portion, the three fluid-filled canals are formed.…”

mentioning

confidence: 99%

“…As the development of the ear progresses to the otocyst stage, the expression domains of these and other genes become confined to particular regions of the epithelium destined to give rise to specific inner ear structures (Fekete and Wu 2002). This refinement of gene expression within the otic vesicle is also dependent on extrinsic signals derived from neighboring tissues as evidenced by the growing number of mouse mutants exhibiting inner ear phenotypes that result from aberrant gene function in the neural tube and surrounding tissues (Chang et al 2004a). Previous work by our group and others described a role for Shh in promoting ventral otic fates Riccomagno et al 2002).…”

mentioning

confidence: 99%

Wnt-dependent regulation of inner ear morphogenesis is balanced by the opposing and supporting roles of Shh

Riccomagno¹,

Takada²,

Epstein³

2005

Genes Dev.

227

314

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The inner ear is partitioned along its dorsal/ventral axis into vestibular and auditory organs, respectively. Gene expression studies suggest that this subdivision occurs within the otic vesicle, the tissue from which all inner ear structures are derived. While the specification of ventral otic fates is dependent on Shh secreted from the notochord, the nature of the signal responsible for dorsal otic development has not been described. In this study, we demonstrate that Wnt signaling is active in dorsal regions of the otic vesicle, where it functions to regulate the expression of genes (Dlx5/6 and Gbx2) necessary for vestibular morphogenesis. We further show that the source of Wnt impacting on dorsal otic development emanates from the dorsal hindbrain, and identify Wnt1 and Wnt3a as the specific ligands required for this function. The restriction of Wnt target genes to the dorsal otocyst is also influenced by Shh. Thus, a balance between Wnt and Shh signaling activities is key in distinguishing between vestibular and auditory cell types.

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“…Another category of inner ear phenotypes that is beyond the scope of this review are mutants with disrupted fluid homeostasis of the inner ear. These inner ear defects are often associated with engorgement or shrinkage of the membranous labyrinth due to fluid imbalance rather than problems in morphogenesis (Cowan et al, 2000, Everett et al, 2001, Chang et al, 2004b, Dravis et al, 2007. In summary, the continual discoveries of inductive signals and their downstream cascades of molecule events for inner ear formation will decode the formation of this complex organ and pave the way for design of strategies to improve hearing and vestibular disorders.…”

Section: Resultsmentioning

confidence: 99%

Patterning and morphogenesis of the vertebrate inner ear

Bok¹,

Chang²,

Wu³

2007

Int. J. Dev. Biol.

Self Cite

129

138

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The positional cues for formation of individual inner ear components are dependent on pre-established axial information conferred by inductive signals from tissues surrounding the developing inner ear. This review summarizes some of the known molecular pathways involved in establishing the three axes of the inner ear, anterior-posterior (AP), dorsal-ventral (DV) and medial-lateral (ML). Signals required to establish the AP axis of the inner ear are not known, but they do not appear to be derived from the hindbrain. In contrast, the hindbrain is essential for establishing the DV axis of the inner ear by providing inductive signals such as Wnts and Sonic hedgehog. Signaling from the hindbrain is also required for the formation of the ML axis, whereas formation of the lateral wall of the otocyst may be a result of first establishing both the AP and DV axes. In addition, this review addresses how genes induced within the otic epithelium as a result of axial specification continue to mediate inner ear morphogenesis. KEY WORDS: inner ear, morphogenesis, vertebrate, axial specification, patterningThe vertebrate inner ear is a highly intricate organ (Figure 1). One of the earliest events during inner ear formation is the acquisition of its axial identity from surrounding tissues. In amniotes, this process most likely begins after otic placode formation and involves early cell fate decisions. These early decisions can be classified into three categories: neural, sensory and non-sensory. Neural-fated cells delaminate from the otic epithelium to form neurons of the cochleovestibular ganglion (CVG). Sensory-fated cells eventually develop into sensory hair cells and supporting cells that form various sensory patches within elaborate nonsensory structures. Sensory and non-sensory fated cells most likely interact with each other to coordinate the morphogenetic process. Identifying the inductive signals that confer axial identity and the cascades of molecular and cellular events that follow are essential for elucidating inner ear morphogenesis. Axial specification of the inner earThe locations where otic placodes develop along the body axis are thought to be dependent on Fibroblast growth factors (Fgfs) emanating from the mesoderm, endoderm and hindbrain (Noramly and Grainger, 2002, Ladher et al., 2005). Details of the otic placode inductive process will be covered by other reviews in this issue. Analyses of mouse hindbrain mutants such as kreisler, Hoxa1 and Fgf3 suggest that the lack of Fgf signaling in the hindbrain alone does not affect placode formation but rather affects subsequent morphogenetic events (Kiernan et al., 2002). There is some indication that inner ear malformations in these hindbrain mutants may be due to defects in axial patterning (Choo Int. J. Dev. Biol. 51: 521-533 (2007) al., 2006). In chicken, otic axial specification occurs after placode formation, whereas this process appears to occur much earlier in salamanders (Harrison, 1936, Bok et al., 2005. The timing of axial specification in mi...

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Molecular Genetics of Vestibular Organ Development

Cited by 15 publications

References 194 publications

Molecular evolution of the vertebrate mechanosensory cell and ear

Molecular evolution of the vertebrate mechanosensory cell and ear

Wnt-dependent regulation of inner ear morphogenesis is balanced by the opposing and supporting roles of Shh

Patterning and morphogenesis of the vertebrate inner ear

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