CALCIUM-BINDING PROTEIN (CALBINDIN-D28K) GENE-EXPRESSION IN THE DEVELOPING AND AGING MOUSE CEREBELLUM

Calbindin-D28k (CaBP28k) protein and gene expression were examined in the mouse cerebellum during development and aging utilizing slot and Northern blot hybridization analyses for mRNA levels, Western blot analysis and radioimmunoassay (RIA) for protein levels, and by in situ studies using immunocytochemistry and hybridization cytochemistry on prepared tissue sections. Samples were obtained and analyzed from C57BL/6J mice aged day of birth and postnatal weeks 1, 2, 4, 8, and 120. A specific cDNA and antibody for CaBP28k were utilized in these studies. Analysis of mRNA levels showed a steady rise in CaBP28k mRNA from birth to a peak at postnatal week (3.4-fold increase) and then a decline to steady-state levels at postnatal weeks 4 and 8 (47% reduction of peak level) followed by a reduction of CaBP28k mRNA to birth levels at postnatal week 120. The specificity of the changes observed was tested by reprobing blots with β-actin cDNA. Analysis of CaBP28k protein levels by both Western blot and RIA showed a similar pattern. In situ analysis of CaBP28k mRNA levels, based on hybridization signal (silver grains per cell), demonstrated a rise in cellular CaBP28K mRNA levels which peaked at postnatal week 2 (416.9 ± 52.1) and then declined to steady-state levels by postnatal weeks 4 and 8 (267.4 ± 35.8). Cellular CaBP28k mRNA levels exhibited a dramatic reduction in the aged cerebellum (postnatal week 120; 78.3 ± 16.0). The levels of cellular CaBP28k mRNA corresponded to the intensity of immunoreactive CaBP28k localized by immunocytochemistry. The results are consistent with the hypothesis that CaBP28k may play a critical role in Purkinje cell maturation and maintenance. Decreased CaBP28k gene expression in the aged cerebellum is not simply a consequence of cell loss (remaining viable cells exhibit reduced CaBP28k gene expression). Thus, CaBP28k may have a neuroprotective and maintaining the concentration of CaBP28k in Purkinje cells may be important for their survival. © 1990.