Since cypin promotes local microtubule assembly ( Akum et al., 2004), and our previous studies have only assessed the effects of overexpression and knockdown of cypin by either counting primary and secondary dendrites ( Akum et al., 2004 Charych et al., 2006 Fernandez et al., 2008) or by using conventional Sholl analysis ( Chen and Firestein, 2007 Kwon et al., 2011), it is not yet known whether cypin has region-specific effects on the dendritic arbor. Recently, we developed new Sholl analyses to determine how BDNF acts at subregions of the arbor and found novel action of BDNF at terminal regions of the arbor ( Langhammer et al., 2010). We have found that cypin is a core regulator of dendritogenesis, and two well-studied regulators of dendrite number, brain-derived neurotrophic factor (BDNF) and the small GTPase RhoA, act via cypin-dependent pathways ( Chen and Firestein, 2007 Kwon et al., 2011). Cypin promotes local microtubule assembly in the dendrite by binding tubulin heterodimers, resulting in increased primary and secondary dendrite numbers ( Akum et al., 2004). We identified a protein termed cypin ( cytosolic PSD-95 interactor) as a core regulator of dendritic arborization ( Akum et al., 2004 Fernandez et al., 2008). This detailed reporting of the data allows for morphological analysis to occur on a much smaller scale.Ī major focus of our work is to understand how changes to the dendritic arbor are mediated by various intrinsic and extrinsic factors. Our laboratory developed a semi-automated Sholl analysis program, called Bonfire, that not only performs analysis on the entire arbor but also analyzes subsets of dendrites (primary/secondary/tertiary, root/intermediate/terminal) within the arbor ( Kutzing et al., 2010 Langhammer et al., 2010). Performing this process by hand is time-consuming and introduces inherent variability due to inconsistency and experimenter bias. This analysis reveals the number of branches, branch geometry, and overall branching patterns of neurons ( Caserta et al., 1995). Sholl analysis includes counting the number of dendritic intersections that occur at fixed distances from the soma in concentric circles. Sholl analysis ( Sholl, 1953) has been an instrumental tool in revealing changes to the dendritic arbor as a whole. Disorders in which neuronal morphology is disturbed highlight the importance of proper dendritic shape to the overall functioning of neuronal networks ( Zoghbi, 2003 Kulkarni and Firestein, 2012).Ī number of metrics may be used to identify dendritic arbor morphology ( Uylings and Van Pelt, 2002). The arbor is shaped by intrinsic and extrinsic factors ( Landgraf and Evers, 2005 Libersat, 2005 Santiago and Bashaw, 2014 Dong et al., 2015 Sainath and Gallo, 2015) and can also be influenced by trauma or disease (reviewed in Kulkarni and Firestein, 2012). The overall shape of the dendritic arbor determines the inputs that neurons receive and how inputs are processed, thus affecting synaptic output ( Miller and Jacobs, 1984 Eilers and Konnerth, 1997 Hausser et al., 2000 Vetter et al., 2001 Schaefer et al., 2003 Elston and Fujita, 2014). The development and patterning of dendrites is a tightly regulated process that is essential for proper functioning of the central nervous system. Neurons are polarized cells that send information through a main axon and receive information through highly branched dendrites. Our results suggest that standard Sholl analysis and simple dendrite counting are not sufficient for uncovering local changes to the dendritic arbor. Here, we apply these different Sholl analyses, and a novel Sholl analysis, to uncover previously unknown changes to the dendritic arbor when we overexpress an important regulator of dendrite branching, cytosolic PSD-95 interactor (cypin), at two developmental time points. Previously, we developed a program (titled Bonfire) to facilitate digitization of neurite morphology and subsequent Sholl analysis and to assess changes to root, intermediate, and terminal neurites. However, we have found that this general method often overlooks local changes to the arbor. Generally, changes to the dendritic arbor are assessed by Sholl analysis or simple dendrite counting. There has been significant progress on characterizing extracellular and intrinsic factors that regulate dendrite number by our laboratory and others. When this regulation is aberrant, which occurs during disease or injury, alterations in dendritic shape result in changes to neural circuitry. ![]() 2Graduate Program in Biomedical Engineering, Rutgers University, Piscataway, NJ, USAĭetermining the shape of cell-specific dendritic arbors is a tightly regulated process that occurs during development.1Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ, USA.
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