epidermal-growth-factor and 5-bromo-4-chloro-3-indolyl-beta-galactoside

Recent studies indicate that nephron progenitor cells of the embryonic kidney are arranged in a series of compartments of an increasing state of differentiation. The earliest progenitor compartment, distinguished by expression of CITED1, possesses greater capacity for renewal and differentiation than later compartments. Signaling events governing progression of nephron progenitor cells through stages of increasing differentiation are poorly understood, and their elucidation will provide key insights into normal and dysregulated nephrogenesis, as well as into regenerative processes that follow kidney injury. In this study, we found that the mouse CITED1(+) progenitor compartment is maintained in response to receptor tyrosine kinase (RTK) ligands that activate both FGF and EGF receptors. This RTK signaling function is dependent on RAS and PI3K signaling but not ERK. In vivo, RAS inactivation by expression of sprouty 1 (Spry1) in CITED1(+) nephron progenitors results in loss of characteristic molecular marker expression and in increased death of progenitor cells. Lineage tracing shows that surviving Spry1-expressing progenitor cells are impaired in their subsequent epithelial differentiation, infrequently contributing to epithelial structures. These findings demonstrate that the survival and developmental potential of cells in the earliest embryonic nephron progenitor cell compartment are dependent on FGF/EGF signaling through RAS.

Topics: Adaptor Proteins, Signal Transducing; Animals; Apoptosis Regulatory Proteins; Cell Differentiation; Cell Lineage; Cells, Cultured; Epidermal Growth Factor; Fibroblast Growth Factors; Galactosides; In Situ Nick-End Labeling; Indoles; Membrane Proteins; Mice; Microscopy, Fluorescence; Nephrons; Nuclear Proteins; Phosphatidylinositol 3-Kinases; Phosphoproteins; Polymerase Chain Reaction; ras Proteins; Receptor Protein-Tyrosine Kinases; Signal Transduction; Trans-Activators

Dorsal root ganglion (DRG) neurons extend axons to specific targets in the gray matter of the spinal cord. During development, DRG axons grow into the dorsolateral margin of the spinal cord and projection into the dorsal mantle layer occurs after a ;waiting period' of a few days. Netrin 1 is a long-range diffusible factor expressed in the ventral midline of the developing neural tube, and has chemoattractive and chemorepulsive effects on growing axons. Netrin 1 is also expressed in the dorsal spinal cord. However, the roles of dorsally derived netrin 1 remain totally unknown. Here, we show that dorsal netrin 1 controls the correct guidance of primary sensory axons. During the waiting period, netrin 1 is transiently expressed or upregulated in the dorsal spinal cord, and the absence of netrin 1 results in the aberrant projection of sensory axons, including both cutaneous and proprioceptive afferents, into the dorsal mantle layer. Netrin 1 derived from the dorsal spinal cord, but not the floor plate, is involved in the correct projection of DRG axons. Furthermore, netrin 1 suppresses axon outgrowth from DRG in vitro. Unc5c(rcm) mutant shows abnormal invasion of DRG axons as observed in netrin 1 mutants. These results are the first direct evidence that netrin 1 in the dorsal spinal cord acts as an inhibitory cue for primary sensory axons and is a crucial signal for the formation of sensory afferent neural networks.

Topics: Animals; Axons; Cell Line; Cricetinae; Epidermal Growth Factor; Female; Galactosides; Ganglia, Spinal; Immunohistochemistry; In Situ Hybridization; Indoles; Mice; Mice, Inbred ICR; Models, Biological; Mutation; Nerve Growth Factors; Netrin-1; Neurons, Afferent; Organ Culture Techniques; Pregnancy; Spinal Cord; Tumor Suppressor Proteins