Articles by Samrawit A. Gebre in JoVE
Revealing Neural Circuit Topography in Multi-Color Stacey L. Reeber1, Samrawit A. Gebre1, Nika Filatova1, Roy V. Sillitoe1 1Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University We provide a practical guide for delivering tracers in vivo and use the spinocerebellar pathway as a model system to demonstrate essential steps for successful neuronal circuit analysis in mice. We describe in detail our versatile tracing protocol that exploits wheat germ agglutinin (WGA) conjugated to Alexa fluorophores.
Other articles by Samrawit A. Gebre on PubMed
Neurofilament Heavy Chain Expression Reveals a Unique Parasagittal Stripe Topography in the Mouse Cerebellum Cerebellum (London, England). Sep, 2011 | Pubmed ID: 20127431 Despite the general uniformity in cellular composition of the adult cerebellum (Cb), the expression of proteins such as ZebrinII/AldolaseC and the small heat shock protein HSP25 reveal striking patterns of parasagittal Purkinje cell (PC) stripes. Based on differences in the stripe configuration within subsets of lobules, the Cb can be further divided into four anterior-posterior transverse zones: anterior zone (AZ) = lobules I-V, central zone (CZ) = lobules VI-VII, posterior zone (PZ) = lobules VIII and anterior IX, and the nodular zone (NZ) = lobules posterior IX-X. Here we used whole-mount and tissue section immunohistochemistry to show that neurofilament heavy chain (NFH) expression alone divides all lobules of the mouse Cb into a complex series of parasagittal stripes of PCs. We revealed that the striped pattern of NFH in the vermis of the AZ and PZ was complementary to ZebrinII and phospholipase C ÃŸ3 (PLCÃŸ3), and corresponded to phospholipase C ÃŸ4 (PLCÃŸ4). In the CZ and NZ the stripe pattern of NFH was complementary to HSP25 and corresponded to PLCÃŸ3. The boundaries of the NFH stripes were not always sharply delineated. Instead, a gradual decrease in NFH expression was observed toward the edges of particular stripes, resulting in domains comprised of overlapping expression patterns. Furthermore, the terminal field distributions of mossy and climbing fibers had a complex but consistent topographical alignment with NFH stripes. In summary, NFH expression reveals an exquisite level of Cb stripe complexity that respects the transverse zone divisions and delineates an intricately patterned target field for Cb afferents.
Fluorescence Mapping of Afferent Topography in Three Dimensions Brain Structure & Function. Sep, 2011 | Pubmed ID: 21387082 Neural circuits are organized into complex topographic maps. Although several neuroanatomical and genetic tools are available for studying circuit architecture, a limited number of methods exist for reliably revealing the global patterning of multiple topographic projections. Here we used wheat germ agglutinin (WGA) conjugated to Alexa 555 and 488 for dual color fluorescent mapping of parasagittal spinocerebellar topography in three dimensions. Using tissue section and wholemount imaging we show that WGA-Alexa tracers have three main characteristics that make them ideal tools for analyses of neural projection topography. First, the intense brightness of Alexa fluorophores allows multi-color imaging of patterned afferent projections in wholemount preparations. Second, WGA-Alexa tracers robustly label the entire trajectory of developing and adult projections. Third, long tracts such as the adult spinocerebellar tract can be traced in less than 6Â h. Moreover, using WGA-Alexa tracers we resolved a level of complexity in the compartmentalized topography of the spinocerebellar projection map that has never before been appreciated. In summary, we introduce versatile tracers for rapidly labeling multiple topographic projections in three dimensions and uncover wiring complexities in the spinocerebellar map.
Parasagittal Compartmentation of Cerebellar Mossy Fibers As Revealed by the Patterned Expression of Vesicular Glutamate Transporters VGLUT1 and VGLUT2 Brain Structure & Function. Aug, 2011 | Pubmed ID: 21814870 The cerebellum receives sensory signals from spinocerebellar (lower limbs) and dorsal column nuclei (upper limbs) mossy fibers. In the cerebellum, mossy fibers terminate in bands that are topographically aligned with stripes of Purkinje cells. While much is known about the molecular heterogeneity of Purkinje cell stripes, little is known about whether mossy fiber compartments have distinct molecular profiles. Here, we show that the vesicular glutamate transporters VGLUT1 and VGLUT2, which mediate glutamate uptake into synaptic vesicles of excitatory neurons, are expressed in complementary bands of mossy fibers in the adult mouse cerebellum. Using a combination of immunohistochemistry and anterograde tracing, we found heavy VGLUT2 and weak VGLUT1 expression in bands of spinocerebellar mossy fibers. The adjacent bands, which are in part comprised of dorsal column nuclei mossy fibers, strongly express VGLUT1 and weakly express VGLUT2. Simultaneous injections of fluorescent tracers into the dorsal column nuclei and lower thoracic-upper lumbar spinal cord revealed that upper and lower limb sensory pathways innervate adjacent VGLUT1/VGLUT2 parasagittal bands. In summary, we demonstrate that VGLUT1 and VGLUT2 are differentially expressed by dorsal column nuclei and spinocerebellar mossy fibers, which project to complementary cerebellar bands and respect common compartmental boundaries in the adult mouse cerebellum.