MICROARRAY STUDIES – AN INTEGRATIVE
PLATFORM FOR CASE-CONTROL STUDIES AND ANIMAL MODELS OF SCHIZOPHRENIA
Jennifer Taylor, Francois Feron,
Darryl Eyles, Jillanne Brown, Alan Mackay-Sim, Nicholas Hayward, Bryan Mowry,
John McGrath
Profiling the human transcriptome using
microarray technology offers an exciting opportunity to unravel the biology of
complex psychiatric disorders. Gene expression analyses of post-mortem
brain tissue in schizophrenia have provided new leads for schizophrenia research
but have limitations due to unavoidable post-mortem changes. Our group has
developed complementary approaches by applying microarray technology to human
fibroblast cultures obtained at biopsy and to an animal model of a putative risk
factor for schizophrenia.
Primary fibroblast cultures were
established for RNA extraction from 10 individuals with schizophrenia and 10
well controls. Expression profiling was carried out using cDNAs arrays
constructed with the Human Unigene 4.5K set. Generated data underwent
preprocessing, normalization and data mining procedures using GeneSpringä
Silicon Genetics. Striking similarities were found with data generated
from post-mortem brain tissue. As in post-mortem prefrontal tissue,
transcript dysregulation has been found for two neurotransmitters (GABA receptor
and glutamate transporter), a G protein regulator (RGS4), several interleukins
and other second messenger elements. In addition, several misexpressed
transcripts suggest a role for pituitary hormones in schizophrenia.
Data-mining has proposed the existence of several subtypes within the affected
sample, apparently driven primarily by variations in the GABAergic and
glumatergic neurotransmitter systems.
In parallel with the human study, we
examined gene expression in an animal model of a novel candidate risk factor for
schizophrenia (low prenatal vitamin D). Rat pups born to vitamin
D-depleted mothers were depleted until birth, weaning or adulthood.
Control rats had normal vitamin D intake. At 10 weeks, mRNA was extracted
from brains (n=10/group) and analyzed using rate genome U34A arrays (8800 genes;
Affymetrix). Gene expression was markedly dysregulated in the adult brain
of the “prenatally- depleted/ repleted-at-weaning” group, with
substantial down-regulation of mRNA transcripts for proteins involved in
neurotransmission (GABA receptor and glutamate transporter); synaptic function
(12 synaptic proteins); cytoskeleton maintenance (4 proteins); cell cycle
control (3 proteins); and signal transduction (4 signalling proteins). In
animals that remain depleted until adulthood, we found a substantial
down-regulation of mRNA transcripts for prolactin, growth hormone and other
lactogen-related proteins.
Several transcripts are proposed for
further verification and candidate analysis on the basis that they appear to be
differentially expressed in human fibroblasts, animal studies and post-mortem
brain tissue studies. We propose that the integration of data from
multiple sources has heuristic value in the interpretation of microarray studies
in schizophrenia.
The project was supported by the
Stanley Foundation.
Poster: