Glia Induce Dendritic Growth in Cultured Sympathetic Neurons by Modulating the Balance between Bone Morphogenetic Proteins (BMPs) and BMP Antagonists

Abstract

Dendritic growth in cultured sympathetic neurons requires specific trophic interactions. Previous studies have demonstrated that either coculture with glia or exposure to recombinant bone morphogenetic proteins (BMPs) is both necessary and sufficient to induce dendrite formation. These observations led us to test the hypothesis that BMPs mediate glial-induced dendritic growth. In situ hybridization and immunocytochemical studies indicate that the spatiotemporal expression of BMP5, -6, and -7 in rat superior cervical ganglia (SCG) is consistent with their proposed role in dendritogenesis. In vitro, both SCG glia and neurons were found to express BMP mRNA and protein when grown in the presence or absence of the other cell type. However, addition of ganglionic glia to cultured sympathetic neurons causes a marked increase in BMP proteins coincident with a significant decrease in follistatin and noggin. Functional assays indicate that glial-induced dendritic growth is significantly reduced by BMP7 antibodies and completely inhibited by exogenous noggin and follistatin. These data suggest that glia influence the rapid perinatal expansion of the dendritic arbor in sympathetic neurons by increasing BMP activity via modulation of the balance between BMPs and their antagonists.

Pincher-Mediated Macroendocytosis Underlies Retrograde Signaling by Neurotrophin Receptors

“…Transient transfection with Lipofectamine 2000 (Invitrogen) was used to introduce constructs containing HA-Pincher, HA-PincherG68E, TrkA, and EGFR/TrkB into PC12 cells and neuronal cultures that were seeded on polylysine plus laminincoated coverslips. SCG neurons were maintained in C2 medium (Lein et al, 2002) supplemented with 100 ng/ml NGF for 24 h, at which time the cells were washed two times with and transfected in DMEM. After 4 h, the cells were washed two times and incubated in DMEM supplemented with 10% FBS, 100 ng/ml NGF for 48 h. Hippocampal neurons grown on polylysine-coated coverslips were transfected after 5 d of culture as described above for SCGs.…”

Dendrite Complexity of Sympathetic Neurons Is Controlled during Postnatal Development by BMP Signaling

“…BMP-5) and NGF dendrites are observed and dendrite numbers/ neuron increase during a culture period of 4 weeks to the number of dendrites present in vivo (5-7; Lein et al, 1995Lein et al, , 2002Beck et al, 2001). Here, we confirm the effect of BMPs on dendrite number in cultures of postnatal mouse SCG and demonstrate similar quantitative effects by BMP-7 and BMP-4 (Fig.…”

“…It should be noted that for convenience we have used shorter culture periods and lower BMP levels as compared with previous studies . This explains, together with the lower dendrite number in mouse sympathetic neurons (four dendrites/neuron; Ruit and Snider, 1991) the quantitatively smaller effects observed compared with rat SCG cultures (Lein et al, 1995). To characterize the BMP effect in more detail, dendrite morphologies were followed by imaging, tracing, and 3D-reconstruction.…”

“…Dendrite complexity is controlled by transcription factors involved in neuron-subtype specification (Grueber et al, 2003;Gaudillière et al, 2004;Hand et al, 2005). However, dendrite development also depends on environmental signals, including members of the neurotrophin family affecting growth and branching of sympathetic (Snider, 1988) and cortical neurons (McAllister et al, 1997) and members of the bone morphogenetic protein (BMP) family controlling dendrite development in cultures of sympathetic neurons (Lein et al, 1995), hippocampal (Withers et al, 2000), cortical (Le Roux et al, 1999), and retinal ganglion cells (Hocking et al, 2008). Sympathetic neurons cultured in the presence of BMPs generate dendrites with similar numbers and branching pattern as observed in vivo (Lein et al, 1995) but it was unclear whether BMPs control dendrite development in vivo.…”

The Novel GTPase Rit Differentially Regulates Axonal and Dendritic Growth

“…The most significant difference is that in contrast to hippocampal neurons, sympathetic neurons derived from embryonic rat superior cervical ganglia extend only a single axonal process during the first 24 h in culture, and when these neurons are grown in serum-free medium in the absence of non-neuronal cells, this polarity is maintained for up to 3 months in culture (Bruckenstein and Higgins, 1988). Dendritic growth in sympathetic neurons requires extrinsic cues: coculture with glial cells (Tropea et al, 1988;Lein et al, 2002) or exposure to BMPs in the presence of NGF (Lein et al, 1995) triggers these neurons to form multiple dendrites in addition to a single axon. Thus, to determine whether Rit signaling represents a divergent or convergent mechanism for regulating axonal versus dendritic growth modes in diverse neuronal cell types, we first determined whether Rit is expressed endogenously in sympathetic neurons and then analyzed the effects of manipulating Rit activation on axonal and dendritic growth in sympathetic neurons.…”