During central nervous system development, glial cells need to be in the correct number and location, at the correct time, to enable axon guidance and neuropile formation. Repair of the injured or diseased central nervous system will require the manipulation of glial precursors, so that the number of glial cells is adjusted to that of neurons, enabling axonal tracts to be rebuilt, remyelinated and functional. Unfortunately, the molecular mechanisms controlling glial precursor proliferative potential are unknown. We show here that glial proliferation is regulated by interactions with axons and that the Drosophila gene prospero is required to maintain the mitotic potential of glia. During growth cone guidance, Prospero positively regulates cycE promoting cell proliferation. Neuronal Vein activates the MAPKinase signalling pathway in the glia with highest Prospero levels, coupling axon extension with glial proliferation. Later on, Prospero maintains glial precursors in an undifferentiated state by activating Notch and antagonising the p27/p21 homologue Dacapo. This enables prospero-expressing cells alone to divide further upon elimination of neurons and to adjust glial number to axons during development
The control of the rate of cell division enables cells to respond to signals from other cells and this promotes the emergence of order as cell mass increases during growth. Glial cell proliferation is coupled to axon guidance, and the sequential deployment of glial cells in constrained numbers enables the sequential sorting out of axons into appropriate trajectories through time. 1 This is achieved by the neuron-dependent regulation of glial division at the G 1 phase. Early on, Prospero plays a key role controlling the G 1 phase and it enables the glia to proliferate in response to neurons. Later, Prospero maintains subsets of glia in G 1 arrest, retaining mitotic potential, whereas non-Prospero glia terminally differentiate. Only this population of Prospero quiescent precursors can overproliferate when neurons are eliminated, inducing a repair response. It is compelling to investigate whether the vertebrate homologue Prox1 may enable the repair response of vertebrate glia.
Purpose The purpose of this study is to identify building contractors’ views as to the need for, impact of and barriers to the use of project bank accounts (PBAs) in the UK construction industry. Design/methodology/approach A cross-sectional research study was carried out by the use of questionnaires to collect quantitative data. The population for the research was of construction professionals working as full-time employees for either main (Tier 1) or specialist contractors (Tiers 2-4). Findings Contractors consider PBAs as an effective initiative to encourage fair payment. There is uncertainty, however, as to whether PBAs will result in project cost savings. Head contractor resistance is perceived to be the biggest barrier to the use of PBAs. Adoption of PBAs in private-sector construction projects is likely to be slow. Research limitations/implications The relative infancy of PBA usage in the construction industry means that responses are largely based on awareness as opposed to experience. Nevertheless, survey data represent a snapshot of contractors’ perceptions with respect to PBAs, which may be used as a benchmark against which to compare future studies to monitor how contractors’ views and expectations have changed with time. Originality/value The survey results will be of particular interest to those international jurisdictions who are considering, or who have already embarked on, the path of trialling and/or using PBAs in the public sector.
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