[PubMed] [Google Scholar] 88

[PubMed] [Google Scholar] 88. neurotrophins, VGF, cortical development, ELISA During development of the cerebral cortex, complex cell-to-cell and cell-to-environmental interactions underlie the generation of cellular diversity necessary for a functionally mature cortex. Although the acquisition of the full complement of features that defines each given cell type occurs over the entire period of development, the specification of each unique trait occurs in a time-dependent manner. For example, certain phenotypic features, including the expression of regionally restricted genes, such as the limbic system-associated membrane protein (LAMP), and laminar position, are specified early, while the progenitor cell is usually mitotically active (McConnell and Kaznowski, 1991; Ferri and Tyk2-IN-7 Levitt, 1993, 1995; Cohen-Tannoudji et al., 1994; Ferri et al., 1996; Frantz and McConnell, 1996; Eagleson et al., 1997; Levitt et al., 1997;Miyashita-Lin et al., 1999; Bishop et al., 2000). Many of these features are stable and remain unaffected by subsequent environmental interactions. Other phenotypic characteristics are regulated later in time and their expression is usually often dynamic, reflecting the changing environment of the cell as development Tyk2-IN-7 proceeds. For instance, the profile of neuropeptides and calcium-binding proteins expressed by a postmitotic cortical interneuron changes over time and is influenced by exposure to specific growth factor signals (Nawa et al., 1993; Widmer and Hefti, 1994; Pappas and Parnavelas, 1997; Fiumelli et al., 2000; Wahle et al., 2000). A time-dependent alteration in the expression of thegene, which encodes a neuronal secretory polypeptide (Possenti et al., 1989; van den Pol et al., 1989, 1994), is also seen. In the fetal and early postnatal period, is usually expressed intensely by postmitotic neurons in allo- and mesocortical areas, with little or no expression in primary sensory and motor areas (Snyder et al., 1998b); however, after the second postnatal week the expression of mRNA is usually widespread across most cortical areas (Snyder and Salton, 1998). The mechanisms that underlie the selective expression of genes in the developing cortex are likely to be complex and include multiple signaling systems, yet only a few interactions that mediate such molecular patterning have been defined (for review, see Ragsdale and Grove, 2001). We have developed an assay to examine more readily the potential of individual cortical progenitors and young neurons to express different molecular markers with differentiation, as well as to identify specific environmental cues that may regulate the expression of these phenotypes. We have shown previously that erbB signaling can modulate expression of the cell-adhesion molecule LAMP (Ferri and Levitt, 1993, 1995; Ferri et al., 1996; Eagleson et al., 1997, 1998). In the present study, we focused on identifying the signals that are responsible for the selective regulation ofin the early developing limbic cortex. We first examined whether there are intrinsic differences between Mouse monoclonal to CD4.CD4 is a co-receptor involved in immune response (co-receptor activity in binding to MHC class II molecules) and HIV infection (CD4 is primary receptor for HIV-1 surface glycoprotein gp120). CD4 regulates T-cell activation, T/B-cell adhesion, T-cell diferentiation, T-cell selection and signal transduction neurons that give rise to expression patterns. MATERIALS AND METHODS Timed-pregnant Holzman Sprague Dawley rats (Harlan Sprague Dawley, Indianapolis, IN) were used. The day a vaginal plug was observed was designated as embryonic day 0 (E0). All chemicals were obtained from Sigma (St. Louis, MO) and culture media and supplements were supplied by Life Technologies (Grand Island, NY) unless otherwise stated. Neuronal cultures were prepared from regions of the E17 rat cerebral wall corresponding to presumptive perirhinal or occipital cortex, as described previously (Ferri and Levitt, 1993; Eagleson et al., 1997). Briefly, pregnant rats were anesthetized with an overdose of sodium pentobarbital; the embryos were then removed and placed in a altered Earl’s balanced salt answer (EBSS) on ice. Next, the brains were dissected from the skull, the meninges were removed, and regions of presumptive perirhinal and occipital cortices were dissected. Homotopic regions from one litter were pooled and incubated in 0.35% collagenaseCdispase (Boehringer Mannheim, Indianapolis, IN). Tyk2-IN-7