OVERVIEW OF THE MOST PREVALENT HYPOTHALAMUS-SPECIFIC MESSENGER-RNAS, AS IDENTIFIED BY DIRECTIONAL TAG PCR SUBTRACTION

We applied the directional tag PCR subtractive hybridization method to construct a rat hypothalamic cDNA library from which cerebellar and h ippocampal sequences had been depleted, enriching 20-30-fold for seque nces expressed selectively in the hypothalamus. We studied a sample of 94 clones selected for enrichment in the subtracted library, These cl ones corresponded to 43 distinct mRNA species, about half of which wer e novel, Thirty-eight of these 43 mRNAs (corresponding to 85 of the cl ones in the sample) exhibited enrichment in the hypothalamus; 23 were highly enriched. In situ hybridization studies revealed that one novel species was restricted to cells in a small bilaterally symmetric area of the paraventricular hypothalamus. Other novel mRNAs showed substan tial enrichment in basal diencephalic structures, particularly the hyp othalamus, without restriction to single hypothalamic nuclei. The data suggest that the hypothalamus utilizes at least two distinct strategi es for employing its selectively expressed proteins. Secretory neurope ptides utilized for intercellular communication are produced by functi onally discrete nuclei, while several other proteins are shared by str uctures that are unrelated in their physiological roles but may share biochemical systems.