The role of cellular degeneration in the normal development of (rat) otocyst

Abstract

From day 12 to 16 of gestation a highly circumscribed zone of cellular degeneration has been observed in the otocyst of more than 50 normal rats. This zone appears to be produced by selective or programmed cell death, and results in the elimination of unneeded cellular elements. That cells in this zone are also selectively destroying subcellular organelles as a first step in specialization is also discussed. Programmed cellular death has long been known in other systems and is often an obligatory companion to cellular specialization. The ear now joins the long list of organs which demonstrate this phenomenon.

Apaf1-dependent programmed cell death is required for inner ear morphogenesis and growth

“…Apoptosis has been thought to be responsible for the complete detachment of the mammalian otic vesicle from the surface ectoderm by removing the connecting epithelial stalk after the closure (Marovitz et al, 1976;Represa et al, 1990;Lang et al, 2000). We observed a cluster of apoptotic cells in the region between the surface ectoderm and the endolymphatic duct epithelium in wild-type embryos at E9.5 and E10.5 (Fig.…”

“…These areas include the epithelial cells that transiently connect the surface ectoderm and the otic vesicle during and after its closure, the base of the outgrowing endolymphatic duct, a ventral area above the primordium of the vestibulocochlear ganglion and the ventromedial wall of the growing cochlear duct (Marovitz et al, 1976;Marovitz et al, 1977;Represa et al, 1990;Fekete et al, 1997;Nikolic et al, 2000). In chicken embryos, apoptosis has also been detected in the fusion plates of the semicircular ducts (Fekete et al, 1997).…”

Programmed Cell Death in the Mouse Cochleovestibular Ganglion during Development

“…PCD is also involved in the development of the epithelium of the inner ear [1] and of the external auditory canal (unpublished data), and is essential for the normal development of the mammalian ear. Electron microscopic data are available about PCD in the development of the mammalian inner ear [2]. However, only limited information is available on the spatiotemporal occurrence of PCD in the cochleovestibular ganglion of the mammalian ear during development.…”

Cell proliferation and cell death in the developing chick inner ear: Spatial and temporal patterns

“…Others attempted to understand the molecular control of proliferation in the otocyst; nerve growth factor (NGF), insulin-like growthfactors (IGFs), cyclin-dependent kinase inhibitors, retinoic acid, and proto-oncogenes have all been implicated (Bernd and Represa, 1989;Von Bartheld et al, 1991;León et al, 1995;Chen and Segil, 1999;Sanz et al, 1999). There are descriptions of programmed cell death during inner ear development for the chick , rat (Marovitz et al, 1976;Zheng and Gao, 1997), mouse (Nishikori et al, 1998;Nishizaki et al, 1998a, b), and human (Represa et al, 1990;Jókay et al, 1998;Nishikori et al, 1998). However, there is no direct examination of the spatial and temporal relationship between cell proliferation and cell death in the developing ear for any single species.…”