Ultrastructural detection of nucleic acids within heat shock-induced perichromatin granules of HeLa cells by cytochemical and immunocytological methods.

in Journal of Structural Biology (2009), 166(3), 329-36

The perichromatin granules (PGs) are enigmatic structures of the cell nucleus. The major drawbacks for a biological study are their rare occurrence and their small size in normal conditions. As heat shock ... [more ▼]

The perichromatin granules (PGs) are enigmatic structures of the cell nucleus. The major drawbacks for a biological study are their rare occurrence and their small size in normal conditions. As heat shock has been shown to increase their number, we applied a hyperthermal shock on HeLa cells to investigate the nucleic acid content of PGs by means of cytochemical and immunocytological approaches. These heat shock-induced PGs (hsiPGs) appeared as clusters organized in the form of honeycomb structures and were always associated with some blocks of condensed chromatin, such as the perinucleolar chromatin shell. A stalk connecting the hsiPG to the chromatin could be observed. For the detection of RNA, we applied an immunocytological method involving two anti-RNA antibodies and quantified the gold labelling obtained. The results clearly revealed that hsiPGs contained RNA. Regarding to the detection of DNA, we used three different methods followed by quantitative analyses. The results seemed to indicate that a small amount of DNA was present in hsiPGs. Together, these findings suggest that hsiPGs might be RNP structures associated with particular regions of DNA. [less ▲]

Early identification of inner pillar cells during rat cochlear development.

in Cell & Tissue Research (2009), 337(1), 1-14

Although the structure of the auditory organ in mature mammals, the organ of Corti, is clearly established, its development is far from being elucidated. Here, we examine its spatio-temporal development ... [more ▼]

Although the structure of the auditory organ in mature mammals, the organ of Corti, is clearly established, its development is far from being elucidated. Here, we examine its spatio-temporal development in rats from embryonic day 16 (E16) to E19 by using cytochemical and immunocytochemical methods at the light- and electron-microscope levels. We demonstrate that the organ of Corti develops from a non-proliferating cell zone that is located in the junctional region between two edges of the dorsal epithelium of the cochlear duct. We also reveal that the first cells to develop in this zone are the inner pillar cells, a particular type of non-sensory supporting cell, which arise in the base of the cochlear duct at the boundary between the two ridges at E16. Cell differentiation in this prosensory region continues according to a base-to-apex gradient; the inner hair cells appear in the greater epithelial ridge at E17 and the outer hair cells in the lesser epithelial ridge at E18. At E19, the various cell types of the organ of Corti are in place. Finally, we show that unlike the development of all the supporting cell types of the organ of Corti, the development of inner pillar cells within the prosensory domain seems not to involve Notch1 activation. These results highlight the central role that the inner pillar cells probably play in the development of the organ of Corti. [less ▲]

New insights in mammalian auditory organ development

Conference (2008, October 30)

Although the structure of the auditory organ in mature mammals, the organ of Corti, is clearly established, its development is far from being elucidated. Using cytochemical and immunohistochemical methods ... [more ▼]

Although the structure of the auditory organ in mature mammals, the organ of Corti, is clearly established, its development is far from being elucidated. Using cytochemical and immunohistochemical methods at the light and electron microscope levels, we examined its spatiotemporal development in rats from embryonic day 16 (E16) to E19. At E16, whatever the region of the cochlear studied (base, middle, apex), the organ of Corti was not present. We demonstrate that the organ of Corti develops from a non-proliferative cell zone that is located in the junctional region between the greater epithelial ridge and the lesser epithelial ridge of the cochlear duct and that is characterized by the presence of numerous microvilli. Using the periodic acid-thiocarbohydrazide-silver proteinate method, we revealed that the first cells to develop in this zone are the inner pillar cells, a particular type of nonsensory supporting cells. They arise in the base of the cochlear duct at the boundary between the two ridges at E16. The cell differentiation in this prosensory region continues according to a base-to-apex gradient, the inner hair cells appearing in the greater epithelial ridge at E17 and the outer hair cells in the lesser epithelial ridge at E18. At E19, all the different cell types of the organ of Corti are well in place. We also showed that the development of the inner pillar cells within the prosensory region does not involve Notch1 signaling. These results highlight the central role that the inner pillar cells could play in the development of the organ of Corti. [less ▲]

Sox10 is not necessary for auditory neurons survival

Poster (2008)

An atypical cell during development of the auditory organ : the inner pillar cell

Poster (2007, September)

Although the structure of the auditory organ in mature mammals, the organ of Corti, is clearly established, its development is far to be elucidated. Using cytochemical and immunohistochemical methods at ... [more ▼]

Although the structure of the auditory organ in mature mammals, the organ of Corti, is clearly established, its development is far to be elucidated. Using cytochemical and immunohistochemical methods at the light and electron microscope levels, we examined its spatiotemporal development in rats from embryonic day 16 (E16) to E19. At E16, whatever the region of the cochlear studied (base, middle, apex), the organ of Corti is not present. We demonstrate that the organ of Corti develops from a non-proliferative cell zone that is located in the junctional region between the greater epithelial ridge and the lesser epithelial ridge of the cochlear duct and that is characterized by the presence of numerous microvilli. Using the periodic acid-thiocarbohydrazide-silver proteinate method, we reveal that the first cells to develop in this zone are the inner pillar cells, a particular type of nonsensory supporting cells; they arise in the base of the cochlear duct at the boundary between the two ridges at E16. The cell differentiation in this prosensory region continues according to a base-to-apex gradient, the inner hair cells appear in the greater epithelial ridge at E17 and the outer hair cells in the lesser epithelial ridge at E18. At E19, all the different cell types of the organ of Corti are well in place. We also show that the development of the inner pillar cells within the prosensory region does not involve Notch1 signaling. These results highlight the central role that cells could play the inner pillar in the organ of Corti development. [less ▲]

An unusual cell type of the auditory organ during neonatal development: the inner pillar cells

Poster (2007)

Spatial dynamics of rRNAs within the cell nucleus

Poster (2007)

Role of Sox 10 in the development of the inner ear

Poster (2007)

Prenatal development study of rat corti organ at the morphological level

Poster (2006, September)

Although the structural organization of the mature Corti organ is generally well defined, little is known about its prenatal development. Here, we have examined by photonic and electron transmission ... [more ▼]

Although the structural organization of the mature Corti organ is generally well defined, little is known about its prenatal development. Here, we have examined by photonic and electron transmission microscopies the morphological changes occurring in the cochlear epithelium from the embryonic day 16 to 19 in rat. Moreover, we have used the periodic acid-thiocarbohydrazide-silver proteinate method to detect the glycogen particles on semithin and ultrathin sections of the cochlear duct. At the embryonic day 16 (E16), whatever the region of the cochlear studied (base, medium, apex), the organ of Corti is not present. The cochlear epithelium appears as a pseudostratified epithelium formed formed by two distinct regions according to the presence or the absence of microvilli at the apical surface of cells. The region with the microvilli is on the modiolar side and the presence of microvilli is a characteristic of cells in the greater epithelial ridge (GER). In basal part of the cochlear duct, glycogen particles are visible on ultrathin sections in only one cell. On both sides of this cell, apical part of the epithelium shows microvilli. At E17, on semithin sections of basal and medium parts of cochlear duct, one cell visible on the whole height of the epithelium shows rich content in glycogen . At E18, in the majority of sections realized at the base and medium of the cochlear canal, the organ of Corti is relatively well recognizable. We distinguish principally the inner hair cells but also to a lesser extent the outer hair cells as well as the supporting cells (pillar, phalengeal and Deiters cells).We show that only the pillar cells have a rich content in glycogen. At E19, the organ of Corti is clearly recognizable in all the basal and medium parts of the cochlear duct. By contrast, it is yet differenciated in the apex. These data seem to indicate that the Corti organ in rat develops from base to apex in the greater epithelial ridge starting by the pillar cells. [less ▲]

Sox 10 is not necessary for auditory neurons survival

Poster (2006)