Rohon‐Beard cells in frog development: A study of temporal and spatial changes in a transient cell population

Abstract

The spatial distribution and temporal disappearance of Rohon-Beard cells in the spinal cords of larval and newly metamorphosed Rana pipiens were studied histologically to provide a basis for further research dealing with this particular cell type. It was found that a maximum number of approximately 250 Rohon-Beard neurons have differentiated within the spinal cord of Rana pipiens by larval stage I. The majority of these cells are located in the cephalic end of the spinal cord, with a large number found near the boundary of the anterior quarter and the second quarter of the spinal cord. Fewer cells are found in the third and fourth quarters. There is a gradual degeneration of these cells during larval life so that by stage XXV, which is the completion of the metamorphic climax, there are no normally appearing Rohon-Beard cells present. Degeneration of the Rohon-Beard cells does not progress cephalocaudally with development, but rather there appears to be a nearly equal proportional loss of Rohon-Beard cells in each quarter of the spinal cord at each of the stages studied. All Rohon-Beard cells present during larval development of Rana pipiens are located in a dorsal position close to the midline. At all ages and in each quarter of the spinal cord there are no significant bilateral differences in number of these cells.

A Family of Acid-sensing Ion Channels from the Zebrafish

“…3); none of the other asic genes were expressed in primary sensory neurons at sufficient abundance to be detected by our in situ hybridization. Moreover, we did not detect expression of any zasic in Rohon-Beard cells, the primary sensory cells located in the spinal cord of embryos of lower vertebrates (26,27). The lack of staining of primary sensory neurons may be due to the low abundance of zASIC mRNA in these cells that escaped detection in our whole mount in situ hybridizations.…”

Slow degeneration of zebrafish Rohon‐Beard neurons during programmed cell death

“…Because both RBs and DRG neurons provide the embryo with tactile sensory information and DRG development appears coincident with RB cell death, it has been proposed that DRG neurons not only replace RBs functionally but also play a role in their death (Hughes, 1957;Eichler and Porter, 1981). In zebrafish, some RBs fragment their DNA before DRG axogenesis, thus Williams et al (2000) suggested it was unlikely that early RB death is due to direct interactions with DRG neurons.…”

“…Why RBs die during de-velopment is unknown. In amphibians, the RB population dies gradually and death coincides with dorsal root ganglion (DRG) development (Hughes, 1957;Eichler and Porter, 1981;Lamborghini, 1987; but see Hughes, 1966). Because death occurs at a time when the sensory functions initially mediated by RBs can be taken over by DRG neurons, it has been suggested that an interaction with DRG neurons might trigger RB death (Hughes, 1957), although there is no direct evidence supporting this possibility.…”

Close spatial-temporal relationship between Islet-1-expressing cells and growing primary afferent axons in the dorsal spinal cord of chick embryo

“…Although Rohon-Beard neurons have been well documented in the dorsal spinal cord of cold-blooded vertebrates (Hughes, 1957;Eichler and Porter, 1981;Kuwada, 1986;Lamborghini, 1987;Korzh et al, 1993;Inoue et al, 1994), similar cells have not been described in birds or mammals, and it is, therefore, unclear whether similar guidance mechanisms exist for longitudinal axons in the dorsal funiculus of these higher vertebrates. Ericson et al (1992) reported transiently appearing cells in the dorsal spinal cord of chick embryos, which express Islet-1, LIM homeodomain protein.…”