Ghashghaei Lab
Department of Molecular Biomedical Sciences
North Carolina State University

RESEARCH SUMMARY


Our brains are delicate structures. If damaged or diseased, the outcome can be devastating and irreversible.  This susceptibility is largely due to inability of the adult brain to repair itself, and currently there are no pharmaceutical or other therapeutic approaches to reverse degeneration in the brain.  Discovery of adult neural stem cells in restricted regions has raised hope for a potential new strategy in utilization of endogenous mechanisms for brain repair.  Research in our laboratory is directed toward:  1. Understanding cellular and molecular mechanisms that underlie the development and functioning of adult neural stem cells; 2. Development of methods to control the behavior of adult stem cells and the fate of their daughter cells, for future attempts in utilizing them for brain repair. 

asdas Text Box: Figure 1. The neurogenic systems of the adult brain. Cartoon of a sagittal section of the adult mouse forebrain. Cell specific neurogenesis persists in the dentate gyrus of the hippocampus (blue) and the olfactory bulb (OB, yellow). The newly born cells in these two regions are thought to arise from populations of stem cells, which give rise to distinct neuronal and glial cell types. Newly generated cells destined for the OB are generated from pools of stem cells in the anterior subventricular zone (SVZ, green). Once born, they migrate to the OB, through the rostral migratory stream (RMS, red), where they differentiate into inhibitory interneurons. In the hippocampus, newly generated neurons arise from stem cells in the subgranular zone (purple) and migrate to the dentate gyrus, where they differentiate into granule (mostly excitatory) neurons.

 

The mammalian brain is constructed by coordinated generation of neurons mostly during embryogenesis.  However, neurogenesis persists in restricted germinal zones in the hippocampus and the olfactory bulb of adults (Fig 1).  Newly born cells in these regions are thought to arise from populations of stem cells which develop from stem cells in corresponding regions of the embryo.  We know that the ‘young’ embryonic stem cells and ‘old’ adult stem cells differ in their potential to generate distinct neuronal and glial cell types.  In the adult olfactory bulb, for example, newly generated neurons are derived from stem cells in the subventricular zone, from where they migrate long distances to reach their target and differentiate into inhibitory interneurons.  In contrast the same germinal zones in the embryonic subventricular zone give rise to diverse populations of neurons and glia, which occupy vast regions of the forebrain.  Current efforts in this laboratory are directed toward understanding transcriptional regulatory mechanisms that potentially define the differences between embryonic stem cells of the subventricular zone and their corresponding adult stem cells. 

Attempts to utilize adult neurogenesis as a therapeutic source of new cells for cellular replacement will undoubtedly require methods for transfer of genes into this cellular niche.  In collaboration with Drs. Olsen and Patel (UNC-Chapel Hill) we have successfully generated and used a replication incompetent lentiviral system for transfer of genes into the adult stem cell niche (Fig. 2).  Moreover, we have incorporated a number of transcriptional promoters into our lentiviral vector to drive the expression of multiple genes in adult stem cells de novo.  We are currently utilizing our lentiviral vectors to assess the role of distinct transcriptional regulators in the development and function of adult stem cells in the subventricular zone.  In addition, we are using our vector to induce the reexpression of a number of embryonically active genes in the adult stem cell niche.


asdasd Text Box: Figure 2. Efficiency of a lentiviral vector for gene transfer into the adult stem cell niche. We have successfully infected stem cell niche in the SVZ using a lentiviral vector in vivo, expressing EGFP under the CMV promoter (EIAV-EGFP). A sagittal section of a brain injected with the EIAV-EGFP vector, perfused after 1 week of survival. Stem cells in the SVZ were infected and EGFP expression was passed on to their progeny in the rostral migratory stream and the olfactory bulb (green cells). Inset is a high magnification image of migrating cells in the rostral migratory stream (green) immunoreactive for polysialylated form of neuronal cell adhesion molecular (PSA-NCAM, red), but not astrocytes (blue).
asdasd Text Box: Figure 3. Promoter specific lentiviral vectors to drive expression of genes in the adult stem cell niche. We have successfully infected stem cell niche in the SVZ using a lentiviral vector in vivo, where expression of EGFP is under a promoter of interest (green cells). A high magnification image of the subventricular zone (dispersed green cells) in a brain injected with promoter specific lentiviral vector, perfused after 1 week of survival. The promoter is normally active only in cells that express a novel transcription factor that is under study in our laboratory.

EQUIPMENT AND SKILLS
We continuously utilize techniques from the following fields to address our questions:

  • Neuroanatomy (pathway tracing, neuro-histology)
  • Mouse neurosurgery (factor/lentiviral delivery in vivo)
  • Molecular biology (cloning, northern-, southern-, and western-blotting, in situ hybridization, and immunofluorescence staining)
  • Cell biological techniques (in vitro cell culture, slice cultures, transfection, progeny mapping, FACS)
  • Developmental biology methods (embryonic brain anatomy and mapping)
  • Gene therapy techniques (lentiviral mediated gene transfer)
  • Confocal and multiphoton microscopy (fixed and live time-lapse imaging of cell and slice cultures, see MOVIE)
  • Mouse genetics (generation and characterization of knock-in and transgenic mice)
  • Bioinformatics, Proteomics, and GeneChip Microarrays

PUBLICATIONS
Ghashghaei H.T., Weimer J., Schmid R., Popko B., Kudlow, JE., Anton E.S. Reversing the developmental clock in astrocytes of the adult brain  Submitted.
Yokota Y, Ghashghaei H.T., Anton E.S. Population dynamics within radial glial populations:  cell division, migration, and interactions in the developing cortex. Submitted.
Ghashghaei H.T., and Anton E.S. (2006) Neuronal migration in the postnatal brain Nature Reviews Neuroscience  Accepted.
Ghashghaei H.T., Hilgetag C., Barbas H. (2006)  Sequence of information processing for emotions based on the anatomic dialogue between prefrontal cortex and amygdala.  NeuroImage  Accepted.
Ghashghaei H.T., Weber J., Pevny L., Schmid R., Schwab M.H., Lloyd K.C., Eisenstat D.D., Lai C., Anton E.S. (2006)  The role of neuregulin-ErbB4 interactions on the proliferation and organization of cells in the subventricular zone.  Proceeding of the National Academy of Sciences 103(6): 1930-1935.
Anton E.S.*, Ghashghaei H.T.*, Weber J.L., McCann C., Fischer T.M., Cheung I.D., Gassmann M., Messing A., Klein R., Schwab M.H., Lloyd K.C.K., Lai C. (2004) Receptor tyrosine kinase ErbB4 modulates neuroblast migration and placement in the adult forebrain.  Nature Neuroscience 7(12): 1319-1328. *Authors contributed equally
Barbas H., Saha S., Rempel-Clower N.L., Ghashghaei H.T. (2003) Serial pathways from primate prefrontal cortex to autonomic areas may influence emotional expression. Biomed Central Neuroscience 4(1):1-12.
Ghashghaei H.T. and Barbas H. (2002) Pathways for emotion: interactions of prefrontal and anterior temporal pathways in the amygdala of the rhesus monkey. Neuroscience 115(4):1261-79.
Barbas H., Ghashghaei H.T., Rempel-Clower N.L., and Xiao, D. (2001)  Anatomic basis of functional specialization in prefrontal cortices in primates.  In: Handbook of Neuropsychology, Grafman J. (Ed.), Elsevier Science B.V., Amsterdam, pp. 1–27.
Ghashghaei H.T. and Barbas H. (2001) Neural interaction between the basal forebrain and prefrontal cortices in the rhesus monkey.  Neuroscience 103(3):593-614.
Barbas H., Ghashghaei H.T., Dombrowski S.M., and Rempel-Clower N.L. (1999) Medial prefrontal cortices are unified by common connections with superior temporal cortices and distinguished by input from memory-related areas in the rhesus monkey. Journal of Comparative Neurology 410:343-367.

Individual interested in research conducted in this laboratory should directly contact Dr. Ghashghaei:
E-mail: Troy_Ghashghaei@ncsu.edu