Research reportDifferentially expressed olfactomedin-related glycoproteins (Pancortins) in the brain
Introduction
The central nervous system (CNS) in higher animals is composed of many regions which are both functionally and histologically distinct. What makes one region functionally distinct from others? How different is one region from another? A factor expressed exclusively or predominantly in a specific region appears to be associated with such specificity [3]. A well-known example is the G-protein-coupled receptors, one of which is expressed exclusively in the neurons of the olfactory epithelium and related to olfactory functions [5]. The search for and analyses of genes expressed in a region-specific manner in the CNS are one of the applicable strategies in identifying specific factors or in studying region-specific neuronal functions at the molecular level.
Much effort has been made to search for genes which are expressed in a region-specific manner in the brain. The subtraction method is one strategy used for this purpose 1, 3, 21, 22, 24. Recently, an innovative technique, the messenger RNA (mRNA) differential display method 9, 10, has been developed. This method enables us to compare, identify and acquire genes expressed only under some specific conditions and/or regions 4, 6, 11. With this method, we have been searching for a gene expressed in the pons during the neuronal circuit formation period. One such gene, which we call pancortin, based on its predominant mRNA expression in the cerebral cortex of the adult, is studied in our research.
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Animals
Adult female Wistar rats, weighing approximately 300 g, and newborn pups were used. Rats were purchased from a local vendor (Nippon Clea, Japan). They were housed in a room kept at a constant temperature and humidity and were provided with food and water ad libitum. Diurnal lighting conditions were maintained with lights on from 08:00 to 20:00 h. Pups were delivered from housed Wistar rats which were obtained 2 days prior to full-term pregnancy. Pups were used for experiments within 24 h of
Isolation of a gene which is expressed predominantly in the cortex
We isolated 17 gene fragments through several screenings using the mRNA differential display method (see Section 2). Among them, 11 fragments turned out to be novel after sequencing and DNA Data Base inquiry (GenBank, October, 1993) by DNASIS program (Hitachi, Japan). ISHH with macro-autoradiogram was carried out to examine their regional distribution in the brain. Among 11 novel candidates, one DNA fragment designated as #103 showed strong hybridization signals in the cortex of the adult rat (
Discussion
Pancortins consist of four independent members (designated Pancortin-1 to -4) sharing a common part in the center of their sequences.
Acknowledgements
The first two authors (T.N. and A.N.) contributed equally to this work. We thank Ms. Sachiyo Funai for her assistance with the Western blot analysis and Ms. Ikuyo Jikihara for her work with the electron microscope. This work was supported in part by Naito Foundation, Senri-life Science Foundation and the Ministry of Education, Science, Sports and Culture of Japan (to M.S.). The DNA database accession numbers for mouse Pancortin-1 through -4 are: D78262–D78265.
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Present address: Department of Molecular Neurobiology, Brain Research Institute, Niigata University, Niigata, 951 Japan.