Rocco, Brad
(2015)
QUANTIFICATION OF GAD67 PROTEIN LEVELS IN AXONAL BOUTONS FROM
DISTINCT SUBTYPES OF GABA NEURONS: REDEFINING CIRCUIT LEVEL
ALTERATIONS IN THE PREFRONTAL CORTEX OF SCHIZOPHRENIA.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Cognitive impairments are a core feature of schizophrenia, and arise, in part, from deficits in gamma-amino butyric acid (GABA)-releasing neurons within the prefrontal cortex (PFC). ~30% of neurons in the PFC of schizophrenia have markedly reduced mRNA expression for the 67 kDa isoform of the GABA synthesizing enzyme, GAD67. Nearly all GABA neurons in primate neocortex can be classified into non-overlapping subtypes by expressing the calcium-binding proteins parvalbumin (PV), calbindin (CB), and calretinin (CR). About half of all PV neurons, which are subdivided into basket cells and chandelier cells, lack detectable GAD67 mRNA expression in schizophrenia. GAD67 protein levels are lower in axonal boutons from PV basket cells in PFC layers 3-4, and although GAD67 expression has not been assessed in chandelier cells they may also have lower GAD67 levels. Further, GAD67 expression has not been assessed in CB and CR neurons in the illness but correlative evidence suggests that they are differentially affected. For example, CB neurons coexpress somatostatin (SST) and in schizophrenia lower SST mRNA expression is correlated with lower GAD67 mRNA expression at both the tissue and cellular levels. By contrast, CR mRNA expression is unaltered and does not correlate with lower GAD67 mRNA expression. Therefore, lower GAD67 levels in schizophrenia are predicted to be restricted to PV and CB neurons, though this hypothesis has not been directly tested. Accordingly, we assessed GAD67 expression in chandelier, CB, and CR neurons in the PFC of schizophrenia and matched comparison subjects using quantitative confocal microscopy. This required us to develop a novel technique to identify lipofuscin autofluorescence, which is prominent in human postmortem tissue. We found that the reported marked reduction in GAD67 mRNA expression in only ~30% of neurons in schizophrenia is associated with markedly lower GAD67 protein levels in just a subset of axonal boutons. GAD67 protein levels were trending lower in chandelier cell boutons and were significantly lower in boutons from CB and CR neurons. Our findings suggest that a proportion of PV, CB, and CR neurons have lower GAD67 expression in the PFC of schizophrenia subjects, which may be a consequence of a common mechanism, such as deficits in excitatory drive.
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| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
27 July 2015 |
| Date Type: |
Publication |
| Defense Date: |
4 June 2015 |
| Approval Date: |
27 July 2015 |
| Submission Date: |
22 July 2015 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
169 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
School of Medicine > Psychiatry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
parvalbumin, calbindin, calretinin, chandelier cell, fluorescence confocal microscopy |
| Date Deposited: |
27 Jul 2015 12:22 |
| Last Modified: |
19 Dec 2016 14:42 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/25732 |
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