CALRETININ GENE-EXPRESSION IN THE HUMAN THALAMUS

The localization and levels of expression of the calcium-binding prote in calretinin (CR) in the human thalamus was studied with an in situ h ybridization method applied to formalin-fixed postmortem material from normal individuals. The riboprobe used was generated from a specific fragment of human CR cDNA. As visualized on X-ray film autoradiographs , high levels of CR gene transcript occurred in several thalamic nucle i, including the reticular nucleus, mediodorsal nucleus, rostral intra laminar nuclei (paracentral, central medial and central lateral) and s everal midline nuclei (paraventricular, reuniens and medioventral nucl ei). In the reticular nucleus, neurons expressing CR mRNA were few in number but formed dense and widely distributed clusters. In contrast, virtually all neurons in the rostral intralaminar and midline nuclei e xpressed very high levels of CR mRNA and formed a prominent rim around the mediodorsal nucleus, which contained scattered clusters of labele d neurons. The caudal intralaminar nuclei, principally the centromedia n nucleus, displayed very few neurons expressing CR mRNA. Only the med ial part of the parafascicular nucleus expressed moderate levels of CR mRNA. The nuclei of the ventral group (ventral anterior, lateral and posterior nuclei) were virtually devoid of CR gene transcript. This hi ghly heterogeneous pattern of mRNA expression suggests that CR may be heavily involved in the function of the so-called non-specific nuclei, but not in that of the specific relay nuclei of the human thalamus. T he data also demonstrate that the presence of CR gene transcript can e asily be detected on formalin-fixed sections of the human brain. (C) 1 998 Elsevier Science B.V.