Correlation of the expression level of C1q mRNA and the number of C1q-positive plaques in the Alzheimer disease temporal cortex analysis of C1q mRNA and its protein using adjacent or nearby sections

We compared the expression level of Clq mRNA and the number of Clq-positive plaques in adjacent or nearby brain sections from Alzheimer disease (AD) a nd control cases, Small blocks of temporal cortex were fixed wi th 4% paraf ormaldehyde for 2 days at 4 degreesC. After cryoprotection with solutions c ontaining 10-20% glycerol and 2% dimethylsulfoxide, 40-mum sections were cu t from the tissue blocks. A section from each case was stained by immunohis tochemistry using a C1q antibody, while RNA was purified from adjacent or n earby sections using a combination of proteinase K pretreatment followed by extraction using Trizol reagent. The expression of C1q B chain mRNA was an alyzed in these samples by the reverse-transcription polymerase chain react ion (RTPCR), The intensities of the PCR products were measured by an image analyzer. The expression of C1q B chain mRNA was significantly more abundan t in AD than in control cases (p < 0.05). Immunohistochemical analysis show ed that C1q protein was localized in senile plaques in the AD brain. The nu mber of C1q-positive plaques correlated with the expression level of C1q ge ne (p < 0.05). The present results suggest that C1q protein in senile plaqu es originates is endogenously produced in the AD brain. Copyright (C) 2001 S. Karger AG. Basel.