Function of Gamma-Protocadherins during postnatal neurogenesis in mice
Final Report Abstract
The γ-Protocadherin gene cluster encodes a family of 22 individual cell surface receptors, expressed in synapses in a random monoallelic fashion in the postnatal and adult mouse brain. Gene- targeted mice lacking the full γ-Pcdh complement die shortly after birth. To study the function of γ- Pcdhs during development of SVZ progenitors in adult mice we generated a conditional γ-pcdh allele allowing for functional inactivation upon lentivirus-mediated Cre-recombinase expression. Our studies revealed that γ-pcdh loss had no impact on the proliferation of SVZ progenitors. Notably, some neuroblasts detatched from the RMS and migrated towards deep cortical layers, however the vast majority correctly populated the main olfactory bulb. The γ-pcdh ko progenitors that reached the olfactory bulb showed a marked reduction in dendritic arborization and in addition failed to develop dendritic spines. Our results suggest that functional γpcdh expression in SVZ progenitors is necessary for the correct integration of granule cells into preexisting neuronal circuits. Impaired dendritic development of granule cells after functional loss of γpcdh expression promted us to establish a system allowing us to quantify deficits in neuronal circuit organization. As a proof of principle we therefore developed a virus-based strategy that allowed fluorescent labeling of granule cells and their monosynaptically connected presynaptic partner neurons upon a single stereotaxic injection of rAAV and a glycoproteindeleted rabies virus. Implementation of improved tissue clearing combined with light-sheet fluorescence microscopy permitted imaging of entire granule cell connectivity maps. Thus, we established a novel method for identifying monosynaptic connectivity maps that might in future experiments (please see above) help to better understand neuronal circuit deficits in γ-pcdh ko progenitors. Finally I would like to mention that this technique might aid in understanding and mapping network properties in virtually all stereotaxically targetable neuronal populations in the rodent brain.
Publications
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Charting olfactory connectivity maps by two-color light-sheet fluorescence microscopy. Cell Reports. (2012),2(5):1375-86
Niedworok, C., Schwarz, I., Ledderose, J., Giese, G., Conzelmann, K.K., Schwarz, M.K.
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Maturation of postnatally generated olfactory bulb granule cells depends on functional gamma-protocadherin expression. Scientific Reports. (2013),3:1514
Ledderose, J., Stumpf, S., Schwarz, M.K.
