Brain‐derived neurotrophic factor (BDNF) is a protein that allows the survival of specific neuronal populations. This study reports on the distribution of the BDNF mRNA in the adult mouse brain, where the BDNF gene is strongly expressed, using quantitative Northern blot analysis and in situ hybridization. All brain regions examined were found to contain substantial amounts of BDNF mRNA, the highest levels being found in the hippocampus followed by the cerebral cortex. In the hippocampus, which is also the site of highest nerve growth factor (NGF) gene expression in the central nervous system (CNS), there is approximately 50‐fold more BDNF mRNA than NGF mRNA. In other brain regions, such as the granule cell layer of the cerebellum, the differences between the levels of BDNF and NGF mRNAs are even more pronounced. The BDNF mRNA was localized by in situ hybridization in hippocampal neurons (pyramidal and granule cells). These data suggest that BDNF may play an important role in the CNS for a wide variety of adult neurons.

Abstract. AMOG (adhesion molecule on glia) is a Ca2+-independent adhesion molecule which mediates selective neuron-astrocyte interaction in vitro (Antonicek, H., E. Persohn, and M. . J. Cell Biol. 104:1587-1595). Here we report the structure of AMOG and its association with the Na,K-ATPase. The complete cDNA sequence of mouse AMOG revealed 409; amino acid identity with the previously cloned subunit of rat brain Na,K-ATPase. Immunoaflinitypurified AMOG and the/$ subunit of detergent-purified brain Na,K-ATPase had identical apparent molecular weights, and were immunologically cross-reactive. Immunoaffinity-purified AMOG was associated with a protein of 100,000 Mr. Monoclonal antibodies revealed that this associated protein comprised the or2 (and possibly ix3) isoforms of the Na,K-ATPase catalytic subunit, but not a l. The monoclonal AMOG antibody that blocks adhesion was shown to interact with Na,KATPase in intact cultured astrocytes by its ability to increase ouabain-inhibitable S6Rb+ uptake. AMOGmediated adhesion occurred, however, both at 4°C and in the presence of ouabain, an inhibitor of the Na,KATPase. Both AMOG and the I$ subunit are predicted to be extracellulady exposed glycoproteins with single transmembrane segments, quite different in structure from the Na,K-ATPase ot subunit or any other ion pump. We hypothesize that AMOG or variants of the B subunit of the Na,K-ATPase, tightly associated with an ot subunit, are recognition elements for adhesion that subsequently link cell adhesion with ion transport.

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