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Volga Neuroscience School 2016 Astroglial control of rhythm genesis in the brain
The Role of sin in the Spine Density of Neocortical Neurons
V.A. Salina1 *, E.A. Turovsky1, M.V. Turovskaya1, A.A. Babaev1, V.S. Tarabykin1, M. Rosario2
1 Institute of Biology and Biomedicine, Lobachevsky State University of Nizhny Novgorod, Russia;
2 Institute for Cell and Neurobiology, Center for Anatomy, Charite-Universitatsmedizin Berlin, Germany. * Presenting e-mail: [email protected]
Abstract. Sip1 (also Zfn1b or ZEB2) is a transcription factor that regulates many processes in embryonic development. The expression of Sipl is region-specific in developing cerebral cortex. Sipl begins express starting at E8.5 of development in the neural crest cells and in the developing neural epithelium, then around at E12.5 Sipl transcripts are present in the cortical plate, ventricular zone of the basal ganglion, midbrain and thalamus pons. In the brain of adult mice Sipl expression is detected on white matter of the neocortex, dentate gyrus and hippocampus. The transcription factor of Sipl consists from two clusters of zinc fingers that contributed binding to two spaced sequences of E- box in regulatory regions of target genes, activated Smads - proteins, the chromatin- remodeling corepressor complex NuRD and CtBP-l/2. Also, in human, mutations in one of allele of Sipl gene is a cause the Mowat - Wilson syndrome that is characterized by epilepsy, intellectual disability, severe mental retardation and craniofacial defects (Srivatsa S. and al., 20l5).
The neocortex is the most difficult structure in the brain. The neocortex consists of the white matter, or myelinated axons with unmyelinated fibers, and the grey matter, or neuronal cell bodies.
The neocortex plays an important role in memory, sleep and learning processes. Also the neocortex involved in instrumental conditioning, in the neurological processes and in human cognition (Parthasarathy S. and al., 20l4).
Goal
To investigate the role of Sip1 in the spine density of neocortical neurons.
Methods: to study the dendritic spine density we did the pictures on confocal microscope Leica TLC SL Microsystems using 60x objective and 6x zoom.
Results
We used 23-old electroporation brains of the Sipl- FNC- line with genotype (fl/wt; cre/cre) and the Sipl- F- line with genotype (fl/fl; cre/wt) or (fl/fl; cre/wt). So the dendritic spine density of mutants are not high , they do not have a large spine head, shot spine neck and mushrooms, stubby, thin compared with wild- type in which is better developed the dendritic spine density (Figure 1).
Fig. 1. A - The spine density of dendrites in wild-type; B - The spine density of dendrites in mutants.
Conclusion
The expression of Sipl regulates many different aspects in the embryonic development and adult stage. Dendritic spines are a small structure where store a synaptic strength and they are also involved in electrical signal transduction between neurons. Also they serve to increase the number of possible contacts between nearby neurons. We suppose that low spine density in Sipl knock-out mice decreases the number of contacts between cells and significantly reduces transduction of signal.
Volga Neuroscience School 2016 Astroglial control of rhythm genesis in the brain References
1. Parthasarathy S., Srivatsa S., Nityanandam A., Tarabykin V. Ntf3 acts downstream of Sipl in cortical postmitotic neurons to control progenitor cell fate through feedback signaling. Development. 2014 Sep;141(17):3324-30. doi: 10.1242/dev.114173. Epub 2014 Aug 1.
2. Srivatsa S., Parthasarathy S., Molnár Z., Tarabykin V. Sipl Downstream Effector ninein Controls Neocortical Ax-onal Growth, Ipsilateral Branching, and Microtubule Growth and Stability. Neuron. 2015. Volume 85, Issue 5, Pages 998-1012.
Up- and Down- Regulation of H-Channels Conductance in CA1 Hippocampal Neurons
M.S. Doronin*, Yu.V. Dembitskaya, A.V. Semyanov
Institute of Neuroscience, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia. * Presenting e-mail: [email protected]
N-methyl-D-aspartate receptors (NMDARs) play an important role in induction of long-term potentiation (LTP). During LTP induction activation of synaptic NMDARs also triggers up-regulation of hyper-polarization-activated (h) channels (Fan et al., 2005). In contrast, prolonged activation of extrasynaptic NMDARs down-regulates h-channels (Gh) (Wu et al., 2012). Thus, Gh plasticity depends on synaptic and extrasynaptic NMDARs activation and balances the overall neuronal excitability increased by LTP. However, it remains unknown if this plasticity can be specific to subcellular regions and if local plasticity can affect the average conductance of the whole neuron.
Therefore, we investigated if the Gh up-regulation in one dendritic branch and down-regulation in another branch might occur simultaneously during induction of LTP and control the overall cell conduct-
We used the two-photon imaging and single-photon glutamate uncaging in order to monitor the state of different subcellular compartments. We performed whole-cell patch-clamp recordings in CA1 pyramidal neurons of C57BL/6 mice (male, P28-35) hippocampal slices. Slices were pre-incubated with a specific inhibitor of vacuolar-type H+-ATPase - bafilomycin A1 (4 |M) to prevent the vesicular release. Neurons were loaded with 50 |M Alexa 594 through the patch pipette that enabled us to visualize dendritic shafts and spines by using the two-photon excitation with the 830 nm wavelength. 400 |M MNI-caged-L-glu-tamate was applied to the bath and uncaged with 405 nm laser at the vicinity of several (6-9) dendritic spines for 5-10 ms. Uncaging-induced EPSPs (uEPSPs) were recorded in soma. The spike-time dependent plasticity-inducing (STDP) protocol was applied in order to induce local LTP in specific dendritic spines. In these spines ("active") local glutamate uncaging was combined with somatic current injections triggering theta-bursts of action potentials. The amplitude and half-width of uEPSPs in "active" spines, their neighbors on the same dendritic brunch ("neighbor" spines) and spines at different dendritic brunch ("remote" spines) were compared before and after induction of STDP.
We found a significant decrease in the input resistance of the neurons (n=8, p=0.0234), suggesting that plasticity induction in localized dendritic shafts might affect overall cell conductance. However, we did not observe a significant difference in the amplitude and half-width of uEPSP in "active", "neighbor" or "remote" spines. These results might indicate an important mechanism of homeostasis that controls synaptic strength and cell excitability, acts via h-channels and equilibrate overall cell conductance.
Acknowledgements
This study was supported by the RFBR foundation (research grant 16-34-00961 MO^_a).
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