Expression of the beta-S100 gene in brain and craniofacial cartilage of the embryonic rat.

The distribution of beta-S100 mRNA within the brain and skull of the 14-day rat embryo was determined using in situ hybridization. In nonnervous tissue, signal corresponding to beta-S100 mRNA was prominent within cartilaginous regions. Signal appeared to be confined to chondrocytes and was not observed within undifferentiated cells of the perichondrium. Within the skull, expression of beta-S100 mRNA was prominent in the nasal region and maxillary process as well as within Meckel's cartilage. Signal was also observed within the cranial base of the embryonic skull. In the embryonic brain, beta-S100 mRNA was prominent within the ventricular region of the myelencephalon and could be localized to a layer of cells lining the ventricle. Although beta-S100 mRNA has been shown to accumulate postnatally in the central nervous system, the present results clearly identify high levels of beta-S100 mRNA within specific regions of the embryonic brain and skull.