Reduction of calbindin-28k mRNA levels in Alzheimer as compared to Huntington hippocampus.
Disturbances in calcium homeostasis have been observed to be associated with Alzheimer's and other neurodegenerative diseases. Increased total calcium levels and decreased levels of calcium binding proteins have been found in Alzheimer brain tissue. However, the mechanism behind these disturbances remain unknown. In situ hybridization with tritiated antisense RNA probes for the calcium binding proteins, calbindin-28k and calmodulin, was used to examine the expression of genes coding for these proteins in Alzheimer and Huntington brain tissues matched for age, agonal process and autopsy interval. mRNA levels for calbindin-28k were reduced by 35% in CA1 and CA2 regions of Alzheimer hippocampus, as compared to Huntington control. In contrast, calmodulin expression was unchanged in CA1 but reduced by 30% in CA2. mRNA expression of calbindin-28k and calmodulin in Alzheimer temporal cortex did not differ from control. There were no significant differences in calcium binding protein message levels in cerebellar Purkinje cells between Alzheimer and Huntington control. There was no correlation between calcium binding protein message levels and brain weight, autopsy interval, patient age or the extent of neurofibrillary degeneration. Instead, decreased calbindin-28k expression in Alzheimer-affected hippocampus was due to an increase in the percentage of neurons expressing lower message levels for these proteins.