Po gene expression in cultured Schwann cells

Abstract

This study examines the expression of the major myelin protein gene P0 in cultured Schwann cells, grown on their own or in association with neurons. Many freshly dissociated Schwann cells from actively myelinating nerves express Po mRNA in high abundance. If neurons are not present, signal intensity falls markedly with time so that by 7 days in culture only a basal expression is evident which is negligible compared to the level in vivo. Dorsal root ganglia from embryo day 16 (E16) rats contain no significant levels of Po mRNA but when grown in full myelinating medium (containing serum and embryo extract) increasing expression is seen from 4 to 5 days onward even though myelination does not occur until after the second week. In this intervening period the intensity of P0 mRNA expression is lower than that found in the actively myelinating cell. Neurons from sympathetic ganglia are also capable of inducing P0 mRNA expression. Schwann cells in dorsal root ganglia explants grown in serum-free defined medium do not assemble a basal lamina and will not wrap or myelinate axons. Nevertheless P0 mRNA, but not protein, is expressed in levels similar to those found in full myelinating medium prior to myelination. Such Schwann cells also exhibit galactocerebroside and the sulphatide recognised by the 04 antibody. It appears that in defined medium or in myelinating medium prior to myelination axonal signals can induce P0 mRNA expression to a certain degree. However, full up-regulation is usually associated with the rapid membrane expansion accompanying myelination. Whether this augmented up-regulation is due to further axonal signalling or events in the Schwann cell is unknown, but the results suggest that P0 expression can be regulated at several stages of synthesis.

Sublytic Terminal Complement Complexes Decrease POGene Expression in Schwann Cells

“…1) while decreasing p75 nerve growth factor receptor mRNA expression (Lemke and Chao, 1988;Feltri et al, 1992). P 0 protein expression detected intracellularly in these in vitro cultured secondary SchCs (data not shown) is ϳ10fold less when compared with myelinating SchCs in vivo (Morrison et al, 1991), which may reflect posttranslational modifications that prevented P 0 targeting and insertion into the plasma membrane (Brunden and Podulso, 1987). Despite the differences between these SchCs in vitro and in vivo, the ability to passage SchCs expressing increased and measurable levels of P 0 mRNA in vitro allowed us to study the potential role of TCCs in modulating myelin gene expression.…”

The cyclin-dependent kinase inhibitor p57kip2 is a negative regulator of Schwann cell differentiation and in vitro myelination

“…In contrast to oligodendroglial precursor cells, cultured primary Schwann cells have so far been regarded as blocked in their differentiation (23,24). Here we demonstrate that silencing of p57kip2 expression results in Schwann cell cycle exit, cellular growth, myelin induction, shifted gene expression pattern, and enhanced in vitro myelination.…”

Surface behavior of axolemma monolayers: Physico‐chemical characterization and use as supported planar membranes for cultured Schwann cells

“…On the other hand, neurons can dictate and control many glial cell functions (Neuberger and DeVries, 1992). Besides the control of glial cell proliferation (DeVries et al, 1982;DeVries, 1992;Cassel et al, 1982;Pellegrino and Spencer, 1985;Chen and DeVries, 1989) and myelination (Bunge, 1987;Brunden et al, 1990;Bunge et al, 1990;Morrison et al, 1991), other glial functions affected by axons include expression of chemical mediators such as nerve growth factor and its receptors (Taniuchi et al. 1988), tissue plasminogen activator (Clark et al, 1991), and fibrillary acidic protein (Jessen and Mirsky, 1984;Neuberger and Cornbrooks, 1989).…”