1. Progress in Understanding the Neurobiology of Schizophrenia Daphne Holt, MD, PhD Director of Research, Schizophrenia Clinical and Research Program Department of Psychiatry, Massachusetts General Hospital Schizophrenia Education Day November 10, 2012

2. Overview What causes schizophrenia?
Genes AND environment
What changes occur in the brain in schizophrenia?
Changes in neurotransmitters: dopamine
Changes in brain structure and function
Effects of risk genes on the brain
Summary & the future

3. The overall picture genetic vulnerability,
present from birth
changes in brain structure/function
symptoms
and impaired functioning
stressful prenatal or later-in-life events,
developmental stages

4. Schizophrenia is caused partly by genes that increase vulnerability to developing the disorder
Family studies:
first degree relatives have a 10X higher risk than the average risk level of 1/100
an identical twin has a > 50X higher risk
Adoption studies:
Children of mothers with schizophrenia who are adopted into families without schizophrenia develop schizophrenia at a higher rate than their biologically unrelated adoptive siblings (Kety, 1976, 1978)

5. WHAT WE HAVE RECENTLY LEARNED: there is no one schizophrenia gene
Many common genetic variants (versions of genes) increase risk for schizophrenia very slightly
Over 20 of these commonly found risk variants have been identified during the past 5 years
There are also a few rare genetic variants that increase risk for schizophrenia to a larger extent, called Copy Number Variants (CNVs)
These common and rare risk variants likely interact with each other, and with environmental risk factors, to increase a person’s vulnerability for developing schizophrenia

6. Schizophrenia Genes Environment
EARLY: elevated paternal age, obstetric
complications, viral infections or malnutrition
during the mother’s pregnancy
LATER: cannabis use, urban environment,
being a minority or immigrant
Multiple common genetic variants
with small effects
And rare genetic variants
with larger effects

7. Some of these risk genes probably influence early brain development
This movie of early brain development shows you that there are dramatic changes in the brain during the last trimester of gestation and first year of life, and then brain development slows down a bit and then speeds up again, it appears to be somewhat non-linear. So this early time period is when either an environmentally induced injury or an inherited abnormality in brain development leads to a change in the brain that increases later vulnerability to schizophrenia.
We build surface models from manually (CMA) labeled neonates, then see if we can model the development of the folds at different spatial frequencies, presumably corresponding to primary, secondary and tertiary folding patterns.
Dataset:
Eight normal neonates with corrected gestational ages (cGA) of 31.1, 34, 36.7, 37.5, 38.1, 38.4, and 40.3 weeks. Built a growth model of the newborns’ cortical surface using Gompertz functions in the wavelet domain
Fischl, Yu, Busa, Pienaar and Grant

8. Some of these risk genes may affect the brain indirectly
For example, some of the genetic variants most consistently found to increase risk for schizophrenia are important for the normal, healthy functioning of the immune system
One way these genes might increase risk for schizophrenia:
making it harder for a fetus to get rid of an infection, leading to harmful effects of that infection on the developing brain

9. WHAT WE HAVE RECENTLY LEARNED: many of the genes that increase risk for schizophrenia, also increase risk for other brain disorders
Including Bipolar Disorder, Epilepsy, Attention Deficit Disorder and Autism
There are no “schizophrenia genes”
Rather than causing a specific disorder, genes may lead to changes in particular brain functions, giving rise to specific symptoms:
delusions, hallucinations, mood dysregulation, attentional problems, problems with social interactions

10. WHAT WE HAVE RECENTLY LEARNED: genetic changes that increase risk for schizophrenia are not necessarily inherited over generations
For example, in older fathers, there are more mutations in the DNA carried by sperm cells (compared to younger fathers)
These new, non-inherited mutations by chance may occur in a gene that is important for brain development or function and increase risk for schizophrenia
New changes (“de novo”) in DNA can increase risk for schizophrenia and other brain disorders

11. The overall picture genetic vulnerability,
present from birth
changes in brain structure/function
symptoms
and impaired functioning
stressful prenatal or later-in-life events,
developmental stages

12. There is too much dopamine released by the brain
in people with schizophrenia during psychotic episodes
Laruelle et al, Biol Psych 1999

13. This abnormality is not specific to schizophrenia but to psychosis
 seen in other disorders
Reith et al, 1994
Pearlson et al, 1995

14. WHAT WE HAVE RECENTLY LEARNED: abnormalities in dopamine are present
in those at risk for developing psychosis
Caudate nucleus D2 dopamine receptor binding:
MZ unaffected co-twins > DZ unaffected and healthy co-twins
Caudate
D2 receptor
binding
Hirvonen et al,
Am J Psych 2005

15. Dopamine synthesis in the brain may be greater in
young people who later develop a psychotic disorder,
compared to those who do not
Howes et al, Am J Psych 2011

16. Some brain regions are smaller than average
in some people with schizophrenia
Many studies since then have shown that this increase in the size of the spaces within the brain is associated with having slightly less brain tissue. This study here showed that the cerebral cortex is slightly thinner in people with schizophrenia.
0.001
0.1
0.05
0.001
Kuperberg et al, Arch Gen Psych 2003

17. WHAT WE HAVE RECENTLY LEARNED:
some of these changes in the brain may occur
during the early years of the illness
One really important discovery in the past decade has been that this reduction in brain tissue volume and increase in ventricle size appears to start and then get slightly worse during the first several years of illness. Thus there appears to be an active pathological process that is occuring in the beginning of schizophrenia that may be reversible and treatable if we can understand what is causing it.
There is some debate about which brain regions are most affected by this progressive process-- is it diffuse and generalized, or affecting specific regions like the STG? Here are results from two separate studies of Bob McCarley’s group which show evidence for each hypothesis. In the earlier study, there is evidence that the left STG shows a lot of volume loss over the follow-up period of 1.5 years, while the amygdala-hippocampal complex does not. Here there is a progressive reduction in total neocortical gray matter volumes in schizophrenia, but not in affective disorders and healthy subjects, which is accompanied by increases in total sulcal CSF and lateral ventricle volumes.
Nakamura et al: Longitudinal volume changes over 1.5 years in total neocortical gray matter volumes, cerebral white matter volumes, sulcal CSF and lateral ventricle volumes.
Kasai et al: Longitudinal volume changes over 1.5 years in anterior and posterior STG volumes (yes) and amygdala-hippocampal volumes (none)
Some of the questions remaining include: 1) Is psychosis somehow toxic to neurons? 2) When does this process stop? If it keep going at this rate, pts ventricles would be enormous after 10 years of having the illness and this is not the case– at some point this process slows down. 3) Does treatment have any effect on this process?
Nakamura et al, Biol Psych 2007
Kasai et al, Am J Psych 2003

18. Specific types of therapy may reverse or prevent these changes
One of the most exciting findings recently has been that there are in fact specific types of therapies that may reverse or prevent these progressive changes in the brain.
Eack et al, Arch Gen Psych 2010

19. And lead to improvements in social and cognitive functioning
Eack et al, Arch Gen Psych 2010

20. Cognitive function (and the involved brain regions)
is affected in schizophrenia
 attention and memory capacities can be reduced
The final highly replicated finding in schizophrenia research that I’ll talk about is the finding of impaired prefrontal function. This was first demonstrated using PET in the mid 80s by Daniel Weinberger’s group and others and was later replicated using fMRI here at MGH and was one of the first applications of cognitive neuroscience to the study of a clinical disorder. The idea as you know was to specifically target an area of the brain, in this case the prefrontal cortex, by having people perform a cognitive task which depends upon that part of the brain, in this case, frontal lobe tasks such as the wisconsin card sorting task or the N-back task, which require intact working memory function to be performed well. Patients with schizophrenia perform poorly on working memory and other executive function tasks and their poor performance has been linked to abnormal activation of the prefrontal cortex.
Meyer-Lindenberg et al, Nat Neurosci 2002

21. WHAT WE HAVE RECENTLY LEARNED:
The regions of the brain important for emotional function are also affected in schizophrenia
Controls
People with schizophrenia *
Brain activity to safety signals
Brain activity to threat signals * * D.
Some people with schizophrenia do not respond to signals in the environment
indicating that a situation is safe
SCZ
Holt et al, Arch Gen Psych 2012

22. Abnormalities in cognitive and/or emotional function may give rise to certain symptoms of schizophrenia, such as delusions A. *
CON ND D ** B.
Brain Activity during Safety Signaling:
CON vs. People with delusions (D)
x = 6
*p < .05
** p < .005
Poor safety signaling in schizophrenia:
reduced activity of
the ventromedial prefrontal cortex
Recently our group examined this model by testing whether one function of the prefrontal cortex, fear inhibition, works properly in schizophrenia. We found that healthy people, the controls here in orange, showed normal fear inhibition and normal activation of the prefrontal cortex during fear inhibition, whereas the schizophrenia patients showed no response or a deactivation of this prefrontal region. The patients with active delusions showed the most abnormal responses of the prefrontal cortex during fear inhibition. So it may in fact be the case that poor prefrontal function leads to too much activity in subcortical systems that then generate inappropriate fear responses, leading to paranoia and other types of delusional thinking and hallucinations.
Because impaired safety signaling has been linked to delusions in previous studies, we did an additional exploratory analysis that examined whether there were any differences between the results for patients with active delusions and those without. There were no differences between those groups. However, the analysis did suggest that the abnormality in vmPFC function in the schizophrenia group was driven by the delusional patients.
D > CON
CON > D
p < .05
D = people with schizophrenia with delusions
ND = people with schizophrenia without delusions
CON = controls
Holt et al, Arch Gen Psych, 2012

23. We now have quantitative methods to measure the strength of the connections of the brain

24. * * WHAT WE HAVE RECENTLY LEARNED:
The connections and communication among different brain regions
are affected in schizophrenia
One example: there is reduced communication
between two cortical areas (within the cingulate gyrus) in schizophrenia
0.15
1.0
Correlation (r) * *
Controls
Schizophrenia
Holt et al, Biol Psych 2011,

25. WHAT WE HAVE RECENTLY LEARNED:
Genes influence brain structure and function
in a way we can reliably measure
For example: the number of a particular variant of a gene you have
(Met allele load of the catechol-O-methyltransferase (COMT) gene)
predicts the function of the prefrontal cortex and memory ability
Egan et al, PNAS 2001

26. Ehrlich et al, Neuroimage 2010
These same genetic variants can also influence the basic structure of the brain ?
For example: COMT met allele load predicts amygdala and hippocampal sizes
We can also use information about genetics and the structure or function of the brain in combination, as was done here– you can see that variation in this gene was associated with a linear change in the volume of the amygdala and hippocampus– in order to better understand the effects of schizophrenia risk genes on the brain and how these genes increase vulnerability to schizophrenia.
Ehrlich et al, Neuroimage 2010

27. Some genetic variants exert a larger influence
on brain structure or function in people with schizophrenia
than in people without schizophrenia
Example: MTHFR C677T effects on prefrontal activity during working memory
= Left DLPFC ROI
C/C (n=41) minus T carrier (n=38)
SCHIZOPHRENIA
= Left DLPFC ROI
C/C (n=35) minus T carrier (n=40)
CONTROLS
There is evidence that it is actually complex interactions among susceptibility genes may be what actually confers diagnostic specificity in patterns of brain function– for example variation in the schizophrenia susceptibility gene, methylenetetrahydrofolate (MTHFR) which is an enzyme which regulates COMT function, also affects prefrontal activity, particularly in patients with schizophrenia, and MTHFR genotype interacts with COMT genotype to influence prefrontal efficiency.
In this study, you can see here that the patients with schizophrenia with the detrimental MTHFR genotype (the T carriers) showed impaired prefrontal function. What they also found was that the schizophrenic patients who had the detrimental MTHFR allele (the T) AND the detrimental COMT allele (the val), showed the poorest recruitment of the dorsolateral prefrontal cortex
Roffman et al, PNAS 2009

28. Summary & the future Take home points:
Genetic AND environmental factors play a role in causing schizophrenia
Environmental factors = modifiable risk factors
There are many genes that slightly increase risk for schizophrenia and other disorders  there is no “schizophrenia gene”
There are many subtle changes in brain structure and function that occur in schizophrenia, which are related to changes in cognitive and emotional function and symptoms
Some of these changes may be partially reversible or preventable with new treatments currently in development

29. The Future: High-density microarrays allow rapid, genome-wide assessment
Genomic DNA
Label reference and test DNA and hybridize
Microarrays
Array spotted with computationally designed oligonucleotide probes
PCR amplification (<1.2 kb)
Adaptor ligation
Bglll digested
New improved technology has now allowed us to characterize the entire genetic code of an individual
Modified from: Feuk et al. Nature Reviews Genetics 2006 29

30. The Future: Decreasing cost, increasing throughput of genotyping over time
Taqman (1)
SBE-FP (1)
Sequenom Mass Spec (5)
These methods have been decreasing in cost
Illumina (1536)
Affymetrix (500K) 30

31. 1mm
The Future: higher resolution imaging of brain structure (sub-millimeter)

32. Thank you for your attention!
Questions?