Molecular Brain Research, 18 (1993) 253-258 253 © 1993 Elsevier Science Publishers B.V. All rights reserved 0169-328x/93/$06.00 BRESM 70593 Nonisotopic in situ hybridization of amyloid beta protein precursor in Alzheimer's disease: expression in neurofibrillary tangle bearing neurons and in the microenvironment surrounding senile plaques B.T. Hyman, J.J. Wenniger and R.E. Tanzi Neurology Service, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114 (USA) (Accepted 1 December 1992) Key words." Amyloid fl-protein precursor; mRNA; In situ hybridization; Neurofibrillary tangle; Senile plaque; Hippocampal formation We have used nonisotopic in situ hybridization techniques with biotinylated junctional oligonucleotide probes to study expression of amyloid precursor protein (APP) 695 and 751 mRNA in the hippocampal formation of Alzheimer's disease. Both mRNAs are strongly expressed in neurons of the hippocampal formation, particularly in the dentate gyrus granule cells and the pyramidal neurons of CA3. The patterns of expression of neither APP695 nor APP751 mRNA correlate well with the stereotyped topography of neurofibrillary tangles or senile plaques, which occur primarily in CA1 and subiculum. We double-labeled in situ sections with immunohistochemical reagents for neurofibrillary tangles or senile plaques. Neurons that contain neurofibrillary tangles continue to express APP mRNA. The level of APP695 and APP751 was measured semiquantitatively by optical density measurements in neurons that were close to (within 25/zm) or farther from a senile plaque (more than 100 /zm). There was no increase in expression in neurons in the immediate microenvironment of senile plaques. Our results suggest that no major change in distribution or type of APP mRNA accompanies neurofibrillary tangle or senile plaque development. INTRODUCTION The [3/A4 peptide that is the major constituent of senile plaques 3 is derived from a larger membrane associated protein, the amyloid precursor protein (APP). The gene encoding APP produces at least 5 major transcripts, proteins that are 695, 751, 770, 563 and 365 amino acids in length (APP695, APP751, APP770, APP563, and APP365). The latter 4 are dif- ferentiated from APP695 by an alternatively spliced exon encoding a Kunitz-type serine protease inhibitor domain2,4,12,13,19,22,23,28,30. In situ hybridization studies of the brain have sug- gested that mRNA for both APP695 and KPI-contain- ing APP is localized primarily in neurons. In general, there is no relationship in terms of topography be- tween regions that are vulnerable for neurofibrillary tangle or senile plaque formation, and those that are strongly positive for APP mRNA 1'5'16'18'x8. Immunohis- tochemical data also suggest a neuronal localization of APP 6'17, and, specifically KPI-containing forms of APP 6. Again, in general, both regions vulnerable for neurofibrillary tangles and senile plaques and regions relatively resistant to the development of these lesions contain APP immunoreactivity. In the accompanying paper, we compared the re- gional and cellular distribution of APP695 and APP751 mRNA in the hippocampal formation of Alzheimer and control patients 31. Using a nonisotopic oligonu- cleotide-based in situ hybridization protocol, we found similar patterns of regional distribution for both mRNAs. Alzheimer patients showed a general distri- bution similar to that seen in controls. The study described here examines the questions of whether indi- vidual neurons that develop neurofibrillary tangles con- tinue to produce APP695 and APP751, and whether Correspondence." R.E. Tanzi, Neurogenetics, Neurology Service, CNY 6, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA. Fax: (1) (617) 726-5735. Reprint requests: B.T. Hyman, Neurology Service, Warren 4, Massachusetts General Hospital, Boston, MA 02114, USA.