Morphology of the Vestibular Sense Organ

Wersäll, Jan; Bagger‐Sjöbäck, Dan

doi:10.1007/978-3-642-65942-3_4

Cited by 108 publications

(63 citation statements)

References 42 publications

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“…Interestingly, also in adult vestibular organs, pRb and Rb were expressed in a subset of HCs. Although non-labelled HCs may express pRb levels that are below the detection limit of the methods used, it remains to be determined whether this non-homogenous expression is linked to the morphological classification into type I and type II vestibular HCs (Wersäll and Bagger-Sjöbäck, 1974).…”

Section: Discussionmentioning

confidence: 99%

The retinoblastoma gene pathway regulates the postmitotic state of hair cells of the mouse inner ear

et al. 2005

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Precursors of cochlear and vestibular hair cells of the inner ear exit the cell cycle at midgestation. Hair cells are mitotically quiescent during late-embryonic differentiation stages and postnatally. We show here that the retinoblastoma gene Rb and the encoded protein pRb are expressed in differentiating and mature hair cells. In addition to Rb, the cyclin dependent kinase inhibitor (CKI) p21 is expressed in developing hair cells, suggesting that p21 is an upstream effector of pRb activity. p21 apparently cooperates with other CKIs, as p21-null mice exhibited an unaltered inner ear phenotype. By contrast, Rb inactivation led to aberrant hair cell proliferation, as analysed at birth in a loss-of-function/transgenic mouse model. Supernumerary hair cells expressed various cell typespecific differentiation markers, including components of stereocilia. The extent of alterations in stereociliary bundle morphology ranged from near-normal to severe disorganization. Apoptosis contributed to the mutant phenotype, but did not compensate for the production of supernumerary hair cells, resulting in hyperplastic sensory epithelia. The Rb-null-mediated proliferation led to a distinct pathological phenotype, including multinucleated and enlarged hair cells, and infiltration of hair cells into the mesenchyme. Our findings demonstrate that the pRb pathway is required for hair cell quiescence and that manipulation of the cell cycle machinery disrupts the coordinated development within the inner ear sensory epithelia.

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Section: Discussionmentioning

confidence: 99%

The retinoblastoma gene pathway regulates the postmitotic state of hair cells of the mouse inner ear

et al. 2005

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“…If one compares across animal classes, several morphological features are present in the pigeon utricular macula that may represent general adaptations refined through parallel evolutionary paths for motion detection in terrestrial/aerial environments. For example, as classically described, type I hair cells are present in reptiles, birds, and mammals (Jørgensen 1970(Jørgensen , 1974Vinnikov et al 1965;Wersäll 1956;Wersäll and Bagger-Sjöbäck 1974). In adult amniotes, type I and type II hair cells can be differentiated by a number of morphological (Kevetter et al 1994; Lysakowski and Goldberg 1997;Ricci et al 1996Ricci et al , 1997Rüsch et al 1998) and physiological characteristics (Correia and Lang 1990;Eatock et al 1994;Rennie and Correia 1994;Rüsch and Eatock 1996).…”

Section: Morphology Of the Pigeon Utricular Maculamentioning

confidence: 96%

Afferent Innervation of the Utricular Macula in Pigeons

Zakir

Dickman

2003

Journal of Neurophysiology

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. Biotinylated dextran amine (BDA) was used to retrogradely label afferents innervating the utricular macula in adult pigeons. The pigeon utriclar macula consists of a large rectangular-shaped neuroepithelium with a dorsally curved anterior edge and an extended medioposterior tail. The macula could be demarcated into several regions based on cytoarchitectural differences. The striola occupied 30% of the macula and contained a large density of type I hair cells with fewer type II hair cells. Medial and lateral extrastriola zones were located outside the striola and contained only type II hair cells. A six-to eight-cell-wide band of type II hair cells existed near the center of the striola. The reversal line marked by the morphological polarization of hair cells coursed throughout the epithelium, near the peripheral margin, and through the center of the type II band. Calyx afferents innervated type I hair cells with calyceal terminals that contained between 2 and 15 receptor cells. Calyx afferents were located only in the striola region, exclusive of the type II band, had small total fiber innervation areas and low innervation densities. Dimorph afferents innervated both type I and type II hair cells with calyceal and bouton terminals and were primarily located in the striola region. Dimorph afferents had smaller calyceal terminals with few type I hair cells, extended fiber branches with bouton terminals and larger innervation areas. Bouton afferents innervated only type II hair cells in the extrastriola and type II band regions. Bouton afferents innervating the type II band had smaller terminal fields with fewer bouton terminals and smaller innervation areas than fibers located in the extrastriolar zones. Bouton afferents had the most bouton terminals on the longest fibers, the largest innervation areas with the highest innervation densities of all afferents. Among all afferents, smaller terminal innervation fields were observed in the striola and large fields were located in the extrastriola. The cellular organization and innervation patterns of the utricular maculae in birds appear to represent an organ in adaptive evolution, different from that observed for amphibians or mammals.

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“…For example, there are seven vestibular sensory organs in the chicken (three cristae, two maculae, the lagena, and macula neglecta) and only five major ones in the mouse. The number varies even more among anamniotes (Wersäll and Bagger-Sjöbäck 1974). However, the five vestibular sensory organs in the mouse (three cristae and two maculae) are consistently found among all species of amniotes, including humans.…”

Section: Gross Development Of the Vestibular Apparatusmentioning

confidence: 99%

“…Furthermore, the lateral canal and ampulla are the last among the three canals and ampullae to have arisen during vertebrate evolution and are absent in Agnatha (jawless vertebrates; for a review, see Wersäll and Bagger-Sjöbäck 1974). So far, no genes have been demonstrated to be exclusively expressed in either anterior or posterior cristae even though some genetic mutations differentially affect the two cristae (see below).…”

Section: Genes Expressed In Specific Cristaementioning

confidence: 99%