Using the expression profile of peripheral blood to investigate regulatory pathways in schizophrenia

Schizophrenia is best considered a “two-hit” disease, with a neurodevelopment impairment followed by an additional process in early adulthood. Both are regulated by hormonal (like thyroid and retinols) and signal transduction pathways (like WNT), which in turn have been previously identified in post-mortem brain studies of schizophrenic individuals. While brain studies are fitted for pathology assessment, there are not suitable for searches of a “diagnostic signature” of schizophrenia. In contrast, peripheral blood is easily accessible, and can be used for the study of disease pathways and potentially diagnosis markers. Blood from twenty eight males with DSM-IV schizophrenia under three drug regimens (clozapine, risperidone or haloperidol), and from 10 healthy controls was studied in a microarray platform with 1364 genes belonging to hormonal and signal transduction pathways. Seven genes were differentially expressed between controls and patients with different treatments, and 28 between healthy controls and specific treatments, with four (CTNNA1, GSTM3, HOXA-13 and KRT18) altered in all analyses. While none of these genes has been previously reported in schizophrenia brain studies, many belong to pathways altered in schizophrenia, belonging to chromosomal loci linked to the disease, which warrants additional replication studies to be performed in larger samples. Glass arrays with 2,352 elements were prepared with the aid of the Flexis Robot (Genomic Solutions, UK). Bacteria were grown in LB medium containing ampicillin (250mg/ml). Inserts were amplified by PCR using M13 reverse and forward primers and products were submitted to 1% agarose gel for quality control. cDNA clones with single amplicons were filtrated in Sephadex G50 (GE Healthcare, UK), printed onto Corning glass slides (Corning, USA) and fixed by UV crosslink (Eisen & Brown, 1999; Brentani et al., 2005). There were 1364 unique genes in the array. Those genes were defined trough literature search for genes related to neurodevelopmental pathways. 76 samples (1/2 dye-swaps).