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Nolan A.M.,University College Cork | Collins L.M.,University College Cork | Wyatt S.L.,Molecular Biosciences Research Division | Gutierrez H.,University of Lincoln | O'Keeffe G.W.,University College Cork
Differentiation | Year: 2014

During development, the growth of neural processes is regulated by an array of cellular and molecular mechanisms which influence growth rate, direction and branching. Recently, many members of the TNF superfamily have been shown to be key regulators of neurite growth during development. The founder member of this family, TNFα can both promote and inhibit neurite growth depending on the cellular context. Specifically, transmembrane TNFα promotes neurite growth, while soluble TNFα inhibits it. While the growth promoting effects of TNFα are restricted to a defined developmental window of early postnatal development, whether the growth inhibitory effects of soluble TNFα occur throughout development is unknown. In this study we used the extensively studied, well characterised neurons of the superior cervical ganglion to show that the growth inhibitory effects of soluble TNFα are restricted to a specific period of late embryonic and early postnatal development. Furthermore, we show that this growth inhibitory effect of soluble TNFα requires NF-κB signalling at all developmental stages at which soluble TNFα inhibits neurite growth. These findings raise the possibility that increases in the amount of soluble TNFα in vivo, for example as a result of maternal inflammation, could negatively affect neurite growth in developing neurons at specific stages of development. © 2015 International Society of Differentiation. Source

Collins L.M.,University College Cork | O'Keeffe G.W.,University College Cork | Long-Smith C.M.,University College Cork | Wyatt S.L.,Molecular Biosciences Research Division | And 3 more authors.
NeuroMolecular Medicine | Year: 2013

A greater understanding of the mechanisms that promote the survival and growth of dopaminergic neurons is essential for the advancement of cell replacement therapies for Parkinson's disease (PD). Evidence supports a role for the mitogen-activated protein kinase p38 in the demise of dopaminergic neurons, while mitogen-activated protein kinase phosphatase-1 (MKP-1), which negatively regulates p38 activity, has not yet been investigated in this context. Here, we show that MKP-1 is expressed in dopaminergic neurons cultured from E14 rat ventral mesencephalon (VM). When dopaminergic neurons were transfected to overexpress MKP-1, they displayed a more complex morphology than their control counterparts in vitro. Specifically, MKP-1-transfection induced significant increases in neurite length and branching with a maximum increase observed in primary branches. We demonstrate that inhibition of dopaminergic neurite growth induced by treatment of rat VM neurons with the dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA) in vitro is mediated by p38 and is concomitant with a significant and selective decrease in MKP-1 expression in these neurons. We further show that overexpression of MKP-1 in dopaminergic neurons contributes to neuroprotection against the effects of 6-OHDA. Collectively, we report that MKP-1 can promote the growth and elaboration of dopaminergic neuronal processes and can help protect them from the neurotoxic effects of 6-OHDA. Thus, we propose that strategies aimed at augmenting MKP-1 expression or activity may be beneficial in protecting dopaminergic neurons and may provide potential therapeutic approaches for PD. © 2013 Springer Science+Business Media New York. Source

Hegarty S.V.,University College Cork | Collins L.M.,University College Cork | Gavin A.M.,University College Cork | Roche S.L.,University College Cork | And 4 more authors.
NeuroMolecular Medicine | Year: 2014

Ventral midbrain (VM) dopaminergic (DA) neurons project to the dorsal striatum via the nigrostriatal pathway to regulate voluntary movements, and their loss leads to the motor dysfunction seen in Parkinson's disease (PD). Despite recent progress in the understanding of VM DA neurogenesis, the factors regulating nigrostriatal pathway development remain largely unknown. The bone morphogenetic protein (BMP) family regulates neurite growth in the developing nervous system and may contribute to nigrostriatal pathway development. Two related members of this family, BMP2 and growth differentiation factor (GDF)5, have neurotrophic effects, including promotion of neurite growth, on cultured VM DA neurons. However, the molecular mechanisms regulating their effects on DA neurons are unknown. By characterising the temporal expression profiles of endogenous BMP receptors (BMPRs) in the developing and adult rat VM and striatum, this study identified BMP2 and GDF5 as potential regulators of nigrostriatal pathway development. Furthermore, through the use of noggin, dorsomorphin and BMPR/Smad plasmids, this study demonstrated that GDF5- and BMP2-induced neurite outgrowth from cultured VM DA neurons is dependent on BMP type I receptor activation of the Smad 1/5/8 signalling pathway. © 2014 Springer Science+Business Media New York. Source

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