Other Developmental Signaling Factors

Sonic hedgehog (Shh) is critical for development and the patterning of the ventral brain (McMahon et al., 2003). It is required for progenitor cell maintenance (Machold et al., 2003). Secretion of the Shh protein increases cell proliferation in the SVZ and SGZ and is required for normal proliferation in the SVZ (Lai et al., 2003). Shh receptors, patched and smoothed, are expressed in the SGZ, as well as, in the hippocampus (Traiffort et al., 1999 Lai et al., 2003). 

The transcription factor cAMP response element-binding protein (CREB) is considered to be involved in the regulation of specific phases of adult neurogenesis in the SVZ/olfactory bulb system (Giachino et al., 2005) and in the SGZ for hippocampal neurons (Bender et al., 2001 Nakagawa et al., 2002). 

An adchtional potential source for rachal glia lies in 

Naris occlusion usually involves the closure of one nostril during the early neonatal period and results in decreased sensory input to the ORNs, decreased volume of the ipsilateral olfactory bulb, and decreased proliferation of progenitor cells in the basal OE. When a reversible model is employed, the OE can rapidly recover from these changes with an increase in the number of newly generated neurons in the periglomerular layer, the target of afferent inputs from ORNs (Cummings and Brunjes, 1997). 

An additional potential source for radial glia lies in 

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R ichardson As with String, cyclin E appears to be regulated by developmental signals in particular tissues (L. Jones, H. Richardson R. Saint, unpublished results). The only place where it is really responding to E2F is in the embryonic gut and other endoreplicating tissues (Duronio O Farrell 1995). In other tissues there might be tissue-specific factors that are controlling its expression. 

ORNs are a large population of similar but distinct neurons. The genetic differentiation of such a group is an interesting functional and developmental problem. OR expression clearly is important but it is likely that other proteins are differentially expressed as well. A complex of signaling proteins and transcription factors determines the functional identity of the components of the olfactory network during development. The functional properties of this network during active life are then defined by the interaction of receptors, neurotransmitters... 

A number of mechanistic questions remain regarding the individual proteins that participate in the EPRE binding complex, their interactions with other signaling pathways, and the influence of tissue-specific or developmental stage-specific factors. Further utilization of the zebrafish model system will prove to be a powerful tool for the identification of accessory factors that may influence the transcriptional activity of Nrf2 and for investigating the toxic mechanisms of electrophiles, which activate... 

Apoptosis mediated by p75 requires specific conditions, with regard to cell type, cell cycle stage, developmental stage, injury or stress. This could be due to time in culture, metabolic impairment, hypoxia, or other types of stress signals, such as nerve injury or trauma (Gu et al., 1999). Sensitive cells may be highly susceptible to injury and inflammation and may become more reactive to released growth factors and cytokines by upregulating receptor expression at the site of injury. 

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