article Flashcards
How much people are affected by MDD
Major depressive disorder (MDD) affects approximately 17 percent of the population,
What is predicted in the year 2023 for MDD
it is predicted to be the number two cause of illness worldwide by the year 20203 .
Symptoms of MDD and what does it implicate
- cognitive impairment
- loss of memory,
implicating synaptic dysfunction in the pathophysiology of MDD.
What are the 3 molecular and cellular changes found in mDD patients and how were they discovered and what does all these studies demonstrate
- a reduction of dendritic spine number and function of neurons in PFC in animal models of depression
- Postmortem studies also report morphometric changes in PFC of MDD subjects, including a reduction in neuronal body size
- This is also consistent with brain imaging studies reporting a reduction in the volume of PFC subregions in MDD subjects
Together, these studies suggest a loss of spine number and dendritic arbor although there is no direct evidence demonstrating this type of neuronal atrophy in the brains of MDD subjects
How were the mechanisms of neuronal atrophy and reduced volume of PFC studied in this study
To gain insight into the mechanisms that underlie neuronal atrophy and reduced volume of PFC, we have re-analyzed the data from a prior microarray gene expression study that we conducted of the dlPFC (Brodmann area 9) of MDD subjects and matched controls
What did this study looking at mechanisms of neuronal atrophy and reduced volume of PFC find
- We classified the microarray data with a 5% FDR11and found that about 30% of the downregulated genes in the MDD group could be related to some aspect of synaptic function.
- A more extended range (20% cutoff) identified an additional subset of down-regulated synaptic function-related genes in dlPFC of MDD brains
What synaptic categories were found in this study
- Regulation of synaptic vesicles
- [calmodulin 2, synapsins I and III, Rab3A, amphiphysin, and synaptogyrin 3] - Regulation of synaptic strength [neurogranin]
- Dendritic spine formation [Rab4B]18, and axonal outgrowth and regeneration [tubulins]
What gene alterations have genome-wide expression studies found of MDD
gene alterations of similar functional categories, including 1. cytoarchitecture
- vesicular transport,
- synaptic transmission,
- some of the same synapse-related genes or isoforms of the genes identified here (e.g., subtypes of amphiphysin, synaptogyrin, synapsin, and the Ras superfamily
What did PCR analysis show
PCR analysis demonstrated significant decreases for 5 of the 10 genes, and trends for all but one (amphiphysin) of the remaining genes in the dlPFC of MDD subjects (Table 1).
What did In situ hybridization analysis confirm
1In situ hybridization analysis of the five confirmed genes demonstrates enriched expression in gray matter of dlPFC with a laminar distribution in the middle (synapsin I) or middle and deep layers (calmodulin 2, Rab3A, Rab4B and β-tubulin 4) of dlPFC.
What did Quantitative analysis confirm
Quantitative analysis confirms that levels of these five genes are significantly decreased in MDD subjects compared to controls
What does CUS stand for
chronic unpredictable stress
What did Studies in rodents with chronic unpredictable stress (CUS) show?
Studies in rodents demonstrate that chronic unpredictable stress (CUS), considered one of the most valid rodent models of depression, decreases the expression of synapsin I, calmodulin 2, Rab3A, and Rab4B, but not beta-tubulin 4, in the PFC (Supplementary Fig. 1), suggesting that the decreased levels of these synapse-related genes in MDD result from chronic stress exposure that could contribute to depressive behaviors.
How was dendritic morphology examined
microtubule-associated protein 2 (MAP2) immunohistochemistry
What did the examination of dendritic morphology show and how was it confirmed
evealed decreased staining of dendritic processes in dlPFC layers III through V of MDD subjects relative to controls, which was confirmed by MAP2 immunoblotting of dlPFC micro-punches
What did electron microscopic stereological analysis show
Using electron microscopic stereological analysis, a marked decrease in spine synapse number was observed in MDD subjects compared to controls (Fig. 1h).
What did Co-factor analysis reveale
no significant effects of medication status, age of first episode age of first episode (<40 vs. ≥40 years old), or suicide on synapse number
What did Examination of the transcription factor binding motifs show
Examination of the transcription factor binding motifs in the promoter regions of the decreased synapse-related genes identified 3,266 upstream regulatory elements for 218 transcription factors (TRANSFAC scoring matrix,
12 transcription factor binding sites are localised to where?
Twelve transcription factor-binding sites are localized to the upstream regulatory domain of all of the MDD and CUS-altered synapse-related genes (Fig. 2a).
The rat homologues of these synapse-related genes included what
The rat homologues of these synapse-related genes include eight of the twelve transcription factor regulatory elements .
What did Analysis of the microarray data reveal
Analysis of the microarray data revealed that one of these transcription factors GATA1 is significantly increased in MDD patients
which transcriptions factors were either not significantly changed in MDD
Other transcriptions factors were either not significantly changed in MDD (GKLF and KID31.0- and 1.1-fold, respectively) or were not included in the microarray gene set.
Levels of what GATA isoforms were not altered in MDD compared to controls
Levels of the related GATA-2, 3, and 4 isoforms were not significantly altered in MDD compared to controls.
Co-factor analysis revealed what in GATA1 expression
Co-factor analysis revealed no effect of medication status on GATA1 expression, and no significant differences between all MDD subjects and groups categorized by age of first episode, number of episodes, and suicide, although the number of subjects per subgroup was small
Studies in the CUS rodent model of depression demonstrate what
Studies in the CUS rodent model of depression demonstrate increased Gata1 expression in the PFC, which was completely reversed by chronic administration of fluoxetine (Fig. 2c).
what did anti-depressants for GATA1 MDD and rodents show and why was the difference
The ability of antidepressant treatment to normalize Gata1 expression in rodents but not in MDD could be due to the 1. small number of the medicated and un-medicated subgroups
- treatment resistance
- heterogeneity of the subjects.
what was used to confirm the binding activity of Gata1 to the promoter of the synapse related genes
Confirmed by chromatin immunoprecipitation (ChIP) with a Gata1 antibody followed by PCR for the Gata1 binding region of each gene
Initial studies focused on Rab4B because this class of small GTP-binding protein is required for endosomal recycling that is critical for maintenance of spine size18 and because RAB4B showed the greatest reduction (Table 1).
what did GATA1 antibody chip result in for most genes
For most of the genes, Gata1 antibody ChIP resulted in an enrichment of the promoter compared to mock, control ChIP.
How was the possibility that elevated GATA1 underlies decreased expression of the synapse-related genes and the atrophy of dendritic processes examined
primary neuronal cultures.
What did Expression of a GFP-tagged rAAV-GATA1 vector in cultured cortical neurons do
Significantly decreased the expression of Rab4b
What is FOG1 and what is it regulated by and what was shown
Expression of a cofactor target gene, FOG1, that is positively regulated by GATA1 was significantly increased by viral expression of GATA1
how was dendrite morphology analyzed
To analyze dendrite morphology, neurons were fixed and labeled with anti-GFP, as well as antiMAP2 antibodies
What did Viral expression of GATA1 show and how was it confirmed
Viral expression of GATA1 decreased the complexity of the dendritic arbor the number of spines , and the intensity of MAP2 staining , which was confirmed by western blot analysis
what did Sholl analysis demonstrate
Sholl analysis demonstrated that viral expression of GATA1 significantly decreased the number of dendrite intersections, indicating decreased complexity
how was the effects of GATA1 expression on behavior in rodent models of depression examined
Control or GATA1 viral vectors were infused into the PFC and the expression and location were confirmed by GFP expression
what did infusion of rAAVGATA1 show
Infusion of rAAVGATA1 produced depressive-like behaviors in two established rodent models.
What was found in the forced swim test with infusion of rAAV-GATA1
In the forced swim test, rAAV-GATA1 increased the time spent immobile, a measure of behavioral despair that is reversed by antidepressant treatment
what was found in the earned helplessness model,
In the learned helplessness model, exposing animals to inescapable stress causes escape deficits that are reversed by antidepressant treatment.
during the initial block what did infusions of rAAV-GATA1 show
Infusions of rAAV-GATA1 increased the number of escape failures during the initial block of active avoidance testing, similar to the effects of inescapable stress exposure (Fig. 4d).
during the second block what did infusions of rAAV-GATA1 show and what does this mean
During the second block of active avoidance testing, there was no significant effect indicating that GATA1 delays responding, but does not produce a sustained effect in this model.
Infusion of rAAV-GATA1 had what effect on locomotor activity
Infusion of rAAV-GATA1 did not influence locomotor activity (not shown), indicating that there was no generalized effect on ambulation.
what did further studies show of the effects of rAAV-GATA1 in the forced swim test
Further studies showed that the effects of rAAV-GATA1 in the forced swim test were not reversed by the antidepressant imipramine as expected, since drug treatment would not influence viral expression of GATA1
How was the The influence of GATA1 on depressive behavior caused by chronic stress examined
The influence of GATA1 on depressive behavior caused by chronic stress was examined with a viral knock down strategy, using a small hairpin RNA (shRNA) targeted to GATA1 (rAAV-GATA1shRNA) (Fig. 4e).
The ability of rAAV-GATA1shRNA to effectively decrease Gata1 mRNA was confirmed in what
in cultured cells and rat PFC
What does (rAAV-ScrshRNA) stand for
scrambled control
The rAAV-GATA1shRNA or scrambled control (rAAV-ScrshRNA) was infused into the PFC f rats that were then subjected to the CUS paradigm showed what
shown to increase Gata1 mRNA