Ed from the Rush Religious Orders study (RROS). Quantitative analysis revealed

Ed from the Rush Religious Orders study (RROS). Quantitative analysis revealed a significant downregulation of transcripts encoding regulators of synaptic function including presynaptic vesicle trafficking (e.g., synaptophysin and synaptogyrin), vesicle docking and fusion/release (synaptotagmin and syntaxin 1), and regulators of excitatory postsynaptic function, including Mangafodipir (trisodium) site PSD-95 and Homer1, in CA1 neurons in MCI and AD compared to NCI (Counts et al., 2014). By constrast, synaptic transcript levels were not significantly different between MCI and AD (Counts et al., 2014), consistent with previous single cell analyses of CA1 neurons in AD (Ginsberg et al., 2000, 2004, 2006; Ginsberg and Che, 2005; Mufson et al., 2006). Downregulation of these markers was associated strongly with poor antemortem cognitive status and AD pathological severity (i.e., Braak stage, NIA-Reagan and CERAD diagnosis) (Counts et al., 2014). Previous biochemical studies of protein levels demonstrated similar findings showing a down regulation of postsynaptic proteins such as PSD-95 and drebrin in the MCI hippocampus compared to NCI subjects, which correlated with poor antemortem cognitive test scores (Counts et al., 2012; Sultana et al., 2010; Hatanpaa et al., 1999). The protein drebrin is a regulator of postsynaptic HIV-1 integrase inhibitor 2 site dendritic spine morphogenesis (Hayashi et al., 1996) and is critical for postsynaptic targeting of PSD-95, which is involved in excitatory postsynaptic plasticity (Takahashi et al., 2003). Interestingly, other groups have found an increase in expression of genes related to mitochondrial bioenergetics, protein homeostasis and the SNARE complex in the MCI hippocampus and entorhinal cortex (Berchtold et al., 2014). A number of synaptic genes showed strong significant correlations most notably in the entorhinal cortex, with fewer in the hippocampus, and these genes were related predominantly to synaptic transmission and synaptic plasticity. Changes in expression of genes that facilitate synaptic excitability and plasticity seem to be associated strongly with worse cognition, and changes in expression of genes that inhibit plasticity were associated positively (somewhat paradoxically) with cognitive scores (Berchtold et al., 2014; Counts et al., 2013). Neurotrophin signaling is also severely affected in MCI and AD, with notable downregulation of cognate neurotrophin receptors TrkA, TrkB, and TrkC in CA1 pyramidal neurons, which also correlates with cognitive decline (MMSE and Global Cognitive Score assessments) (Ginsberg et al., 2010a). These synaptic and neurotrophic alterations suggest that the hippocampus displays greater metabolic demand in MCI and ultimately progressive degeneration, if not maintained. These diverse changes in gene expression indicate that there is a rebalancing of synaptic transmission and plasticity and that synaptic gene transcript and protein levels are expressed differentially and altered in discrete cells and regions in the hippocampus in MCI.Author Manuscript Author Manuscript Author Manuscript Author ManuscriptNeuroscience. Author manuscript; available in PMC 2016 September 12.Mufson et al.PageThe underlying pathogenic mechanisms that trigger these structural synaptic alterations in the hippocampus during MCI and the onset of AD are unclear, yet several lines of evidence revealed that an aberrant expression of endosomal-lysosomal proteins occurs within hippocampal neurons even before the SP and NFT formation early in AD (Nixon et.Ed from the Rush Religious Orders study (RROS). Quantitative analysis revealed a significant downregulation of transcripts encoding regulators of synaptic function including presynaptic vesicle trafficking (e.g., synaptophysin and synaptogyrin), vesicle docking and fusion/release (synaptotagmin and syntaxin 1), and regulators of excitatory postsynaptic function, including PSD-95 and Homer1, in CA1 neurons in MCI and AD compared to NCI (Counts et al., 2014). By constrast, synaptic transcript levels were not significantly different between MCI and AD (Counts et al., 2014), consistent with previous single cell analyses of CA1 neurons in AD (Ginsberg et al., 2000, 2004, 2006; Ginsberg and Che, 2005; Mufson et al., 2006). Downregulation of these markers was associated strongly with poor antemortem cognitive status and AD pathological severity (i.e., Braak stage, NIA-Reagan and CERAD diagnosis) (Counts et al., 2014). Previous biochemical studies of protein levels demonstrated similar findings showing a down regulation of postsynaptic proteins such as PSD-95 and drebrin in the MCI hippocampus compared to NCI subjects, which correlated with poor antemortem cognitive test scores (Counts et al., 2012; Sultana et al., 2010; Hatanpaa et al., 1999). The protein drebrin is a regulator of postsynaptic dendritic spine morphogenesis (Hayashi et al., 1996) and is critical for postsynaptic targeting of PSD-95, which is involved in excitatory postsynaptic plasticity (Takahashi et al., 2003). Interestingly, other groups have found an increase in expression of genes related to mitochondrial bioenergetics, protein homeostasis and the SNARE complex in the MCI hippocampus and entorhinal cortex (Berchtold et al., 2014). A number of synaptic genes showed strong significant correlations most notably in the entorhinal cortex, with fewer in the hippocampus, and these genes were related predominantly to synaptic transmission and synaptic plasticity. Changes in expression of genes that facilitate synaptic excitability and plasticity seem to be associated strongly with worse cognition, and changes in expression of genes that inhibit plasticity were associated positively (somewhat paradoxically) with cognitive scores (Berchtold et al., 2014; Counts et al., 2013). Neurotrophin signaling is also severely affected in MCI and AD, with notable downregulation of cognate neurotrophin receptors TrkA, TrkB, and TrkC in CA1 pyramidal neurons, which also correlates with cognitive decline (MMSE and Global Cognitive Score assessments) (Ginsberg et al., 2010a). These synaptic and neurotrophic alterations suggest that the hippocampus displays greater metabolic demand in MCI and ultimately progressive degeneration, if not maintained. These diverse changes in gene expression indicate that there is a rebalancing of synaptic transmission and plasticity and that synaptic gene transcript and protein levels are expressed differentially and altered in discrete cells and regions in the hippocampus in MCI.Author Manuscript Author Manuscript Author Manuscript Author ManuscriptNeuroscience. Author manuscript; available in PMC 2016 September 12.Mufson et al.PageThe underlying pathogenic mechanisms that trigger these structural synaptic alterations in the hippocampus during MCI and the onset of AD are unclear, yet several lines of evidence revealed that an aberrant expression of endosomal-lysosomal proteins occurs within hippocampal neurons even before the SP and NFT formation early in AD (Nixon et.