ABSTRACT
The neuronal protein 25 (NP25), a member of the calponin (CaP) protein family, has previously been identified as neuron-specific protein in the adult rat brain. Here, we show an early onset of NP25 expression in the chick embryo neural tube. NP25 represents, together with NeuroM, one of the earliest markers for postmitotic neurons. To elucidate its function in the developing nervous system, NP25 was overexpressed in E5 and E9 sensory neurons, E7 sympathetic neurons and PC12 cells that show different endogenous NP25 expression levels. Whereas E5 and E9 sensory neurons and PC12 cells, which express low endogenous levels of NP25, responded by enhanced neurite outgrowth, a reduction of neurite length was observed in sympathetic neurons, which already express high endogenous levels of NP25. Knockdown of NP25 in sensory neurons using NP25 siRNA resulted in shorter neurites, whereas reduction of NP25 expression in sympathetic neurons led to increased neurite length. These results suggest a dynamic function for NP25 in the regulation of neurite growth, with an optimal level of NP25 required for maximal growth.
Subject(s)
Calcium-Binding Proteins/metabolism , Microfilament Proteins/metabolism , Nerve Tissue Proteins/metabolism , Neural Tube/metabolism , Neurites/physiology , Neurons/metabolism , Animals , Bromodeoxyuridine , Calcium-Binding Proteins/genetics , Chick Embryo , In Situ Hybridization , Microfilament Proteins/genetics , Nerve Tissue Proteins/genetics , Neurites/metabolism , PC12 Cells , RNA Interference , Rats , CalponinsABSTRACT
Sympathetic neurons are generated through a succession of differentiation steps that initially lead to noradrenergic neurons innervating different peripheral target tissues. Specific targets, like sweat glands in rodent footpads, induce a change from noradrenergic to cholinergic transmitter phenotype. Here, we show that cytokines acting through the gp 130 receptor are present in sweat glands. Selective elimination of the gp 130 receptor in sympathetic neurons prevents the acquisition of cholinergic and peptidergic features (VAChT, ChT1, VIP) without affecting other properties of sweat gland innervation. The vast majority of cholinergic neurons in the stellate ganglion, generated postnatally, are absent in gp 130-deficient mice. These results demonstrate an essential role of gp 130-signaling in the target-dependent specification of the cholinergic neurotransmitter phenotype.
Subject(s)
Adrenergic Fibers/metabolism , Cell Differentiation/physiology , Cytokine Receptor gp130/metabolism , Cytokines/metabolism , Signal Transduction/physiology , Sweat Glands/embryology , Sweat Glands/innervation , Animals , Body Weights and Measures , Cells, Cultured , DNA Primers , Immunohistochemistry , In Situ Hybridization , Mice , Mice, Transgenic , Reverse Transcriptase Polymerase Chain Reaction , Stellate Ganglion/cytology , Stellate Ganglion/metabolism , Sweat Glands/anatomy & histology , Sweat Glands/metabolismABSTRACT
Sympathetic ganglia are composed of noradrenergic and cholinergic neurons. Cholinergic sympathetic neurons are characterized by the expression of choline acetyl transferase (ChAT), vesicular acetylcholine transporter (VAChT) and the vasoactive intestinal peptide (VIP). To investigate the role of cytokine growth factor family members in the development of cholinergic sympathetic neurons, we interfered in vivo with the function of the subclass of cytokine receptors that contains LIFRbeta as essential receptor subunit. Expression of LIFRbeta antisense RNA interfered with LIFRbeta expression and strongly reduced the developmental induction of VIP expression. By contrast, ganglion size and the number of ChAT-positive cells were not reduced. These results demonstrate a physiological role of cytokines acting through LIFRbeta-containing receptors in the control of VIP expression in sympathetic neurons.
