Developmental changes in the translatable mRNA for beta subunit of S-100 protein in rat brain

Gene expression in cells of the central nervous system

This review summarized a part of our studies over a long period of time, relating them to the literature on the same topics. We aimed our research toward an understanding of the genetic origin of brain specific proteins, identified by B. W. Moore and of the high complexity of the nucleotide sequence of brain mRNA, originally investigated by W. E. Hahn, but have not completely achieved the projected goal. According to our studies, the reason for the high complexity in the RNA of brain nuclei might be the high complexity in neuronal nuclear RNA as described in the Introduction. Although one possible explanation is that it results from the summation of RNA complexities of several neuronal types, our saturation hybridization study with RNA from the isolated nuclei of granule cells showed an equally high sequence complexity as that of brain. It is likely that this type of neuron also contains numerous rare proteins and peptides, perhaps as many as 20,000 species which were not detectable even by two-dimensional PAGE. I was possible to gain insight into the reasons for the high sequence complexity of brain RNA by cloning the cDNA and genomic DNA of the brain-specific proteins as described in the previous sections. These data provided evidence for the long 3'-noncoding regions in the cDNA of the brain-specific proteins which caused the mRNA of brain to be larger than that from other tissues. During isolation of such large mRNAs, a molecule might be split into a 3'-poly(A)+RNA and 5'-poly(A)-RNA. In the studies on genomic DNA, genes with multiple transcription initiation sites were found in brain, such as CCK, CNP and MAG, in addition to NSE which was a housekeeping gene, and this may contribute to the high sequence complexity of brain RNA. Our studies also indicated the presence of genes with alternative splicing in brain, such as those for CNP, MAG and NGF, suggesting a further basis for greater RNA nucleotide sequence complexity. It is noteworthy that alternative splicing of the genes for MBP and PLP also produced multiple mRNAs. Such a mechanism may be a general characteristic of the genes for the myelin-specific proteins produced by oligodendrocytes. In considering the high nucleotide sequence complexity, it is interesting that MAG and S-100 beta genes etc. possess two additional sites for poly(A).(ABSTRACT TRUNCATED AT 400 WORDS)

Structure and expression of rat S-100 beta subunit gene

The gene structure for S-100 beta subunit has been elucidated. The gene spans about 8 kbp and consists of 3 exons and 2 introns. The transcription initiation site was determined by an S1 nuclease mapping. The promoter region contains TATA-box-like and CAAT-box-like sequences. To examine the activity of the promoter sequence, a transfection of pS100 beta-lacZ fused gene to the cultured cells was carried out. C6 glioma cells showed a positive expression of beta-galactosidase. Gene-deletion experiments suggested the functional importance of the DNA fragment (22 bp) containing TATA-box-like and CAAT-box-like sequences. A factor protein that binds to the 100 bp DNA fragment containing the promoter sequence was specifically detected in the rat brain nuclear extract.

Expression of the gene encoding the beta-subunit of S-100 protein in the developing rat brain analyzed by in situ hybridization

To investigate patterns of expression of the gene encoding the beta-subunit of S-100 protein during development of the rat brain we have used Northern blotting and in situ hybridization histochemistry. During late prenatal development beta-S-100 mRNA was observed first in the germinal zone lining the 4th ventricle. In the postnatal cerebellum this mRNA accumulated primarily in Bergmann glia and astrocytes of the deep white matter. In the hindbrain, expression of S-100 mRNA increased steadily in specific regions during the first postnatal week while levels remained low in more anterior brain regions. By the end of the second postnatal week, a dense punctate signal was distributed throughout the midbrain and hindbrain. Expression in forebrain, first observed at E18, was confined to cells lining the ventricle until the second postnatal week when accumulation of mRNA was observed in specific regions of the hippocampus, neocortex and olfactory bulb. The adult brain pattern of beta-S-100 mRNA distribution is attained during the third postnatal week. These results demonstrate a caudal-rostral gradient in expression of the beta-S-100 gene during rat brain development, as well as pronounced regional differences which may reflect the differentiation of subpopulations of astrocytes.

Immunohistochemical analysis of the olfactory mucosa by use of antibodies to brain proteins and cytokeratin

The present study deals with the immunohistochemical detection of four brain-derived proteins and cytokeratin in the normal olfactory mucosa of humans and guinea pigs. Neurofilament protein immunoreactivity was found in the olfactory vesicles, dendrites, and perikaryon of receptor cells, and in thick nerve bundles located deep in the lamina propria. The antiserum to neuron-specific enolase (NSE) selectively stained olfactory receptor cells throughout the length of the bundles. The NSE immunoreactivity also was recognized in nerve bundles of various sizes throughout the lamina propria. Glia-specific S-100 protein immunoreactivity was present in Bowman's glands as well as in all nerve bundles in the lamina propria, but not in any cellular elements constituting the olfactory epithelium. Immunoreactivity for spot-35 protein, which was considered to be specific for cerebellar Purkinje cells, was found in flasklike cells (microvillar cells) occurring near the free surface of the epithelium. The basal cells in the olfactory and respiratory epithelium were stained positively with a cytokeratin antiserum.

The ultrastructure of Ruffini endings in the periodontal ligament of rat incisors with special reference to the terminal Schwann cells (K-cells)

The Ruffini endings and associated cells in the periodontal ligament of rat incisors were investigated by means of immunohistochemistry for glia-specific S-100 protein and electron microscopy. Numerous Ruffini endings, which were immunoreactive for S-100 protein as well as for neurofilament protein, were distributed in the alveolus-related part of the lingual periodontal ligament. In electron microscopy, the Ruffini endings displayed expanded axoplasmic spines filled with a large number of mitochondria and neurofilaments; some of the spines directly contacted the surrounding collagen fibers via fingerlike projections. The axoplasmic spines and Schwann sheath, for the most part, were covered alternately by single or multiple layers of the basal lamina. Several rounded cells showing S-100 immunoreactivity occurred in the vicinity of the Ruffini endings. The rounded cells associated with Ruffini endings possessed a kidney-shaped nucleus and enveloped the axoplasmic spines with their cytoplasmic processes. From these morphological features, the cells in question were identified as the K-cells described by Everts et al. (1977). These K-cells developed Golgi apparatus and rough endoplasmic reticulum, suggesting active synthesis of proteins. Immunohistochemistry at the electron microscopic level revealed an intense immunoreactivity for S-100 protein in the cytoplasm of the K-cell and led to a conclusion that the K-cells were terminal Schwann cells associated with Ruffini endings, presumably corresponding to the lamellar cells in the inner bulb of sensory corpuscles.

Novel electrophoretic approach to study of poly(A)+RNA pool heterogeneity in different areas of human postmortem brain

A simple method for fast fractionation of human postmortem brain total poly(A)+RNA has been developed. Guanidine thiocyanate extractable RNA was directly applied on the membranes of cellulose nitrate with immobilized oligo(dT) chains. After the electrophoresis in 35 mM tris-acetete buffer (pH 7.90) containing 10 mM EDTA and 35% formamide, the membranes were washed with the same buffer for removal of nonbinding poly(A)-lacking RNAs. Then, poly(A)+RNA fractions were selectively stained by 3,5-dimethylphenol in the presence of FeCl3 at pH 2.35. Finally, the resulting electrophorograms were scanned at 500 nm for quantitative evaluation of the data.

Innervation of periodontal ligament and dental pulp in the rat incisor: an immunohistochemical investigation of neurofilament protein and glia-specific S-100 protein

Nervous elements in the periodontal ligament and dental pulp of rat incisors were investigated by means of immunohistochemistry for neurofilament protein (NFP) and glia-specific S-100 protein. The periodontal ligament in the incisors was densely innervated by NFP-immunoreactive nerve fibers; the distribution of the nerve fibers and their terminations differed markedly from those in molars. NFP-positive, thick nerve bundles entered the lingual periodontal ligament through slits located in the mid-region of the alveolar socket, and immediately formed numerous Ruffini-like corpuscles. In the labial periodontal ligament, all of the NFP-immunoreactive nerve fibers terminated in free endings. The restricted location of the stretch receptor, Ruffini-like corpuscle, in the lingual periodontal ligament appears to be an essential element, because this region is regularly extended during mastication. The nervous elements were restricted to the alveolar half of the periodontal ligament in every region; they avoided the dental half of the periodontal ligament, which presumably moves continuously with the tooth. Pulpal nerve fibers in incisors also showed a characteristic distribution different from those in molars; individual nerve fibers with beaded structures ran in the center of the pulp toward the incisal edge, and did not form the subodontoblastic nerve plexus of Raschkow. Immunostaining for S-100 protein revealed a distribution pattern of nervous elements similar to that for NFP, suggesting that the nerves supplying the periodontal ligament and dental pulp were mostly covered by a Schwann sheath.

Immunohistochemical method for the diagnosis of olfactory disturbance

To confirm the diagnosis and determine the cause of the olfactory disturbance, we used an immunohistochemical method to examine biopsy specimens of the olfactory mucosa from a patient who complained of anosmia after head injury. Neuron-specific enolase immunoreactivity was found in the olfactory vesicles and dendrites of the receptor cells in the olfactory epithelium. S-100 protein immunoreactivity was found in the ductal cells of Bowman's gland in the olfactory epithelium and in the acinar cells of Bowman's gland in the lamina propria. This suggests that the olfactory receptor cells and Bowman's gland were normal. The olfactory disturbance in this patient was not caused by nerve transection due to the head injury, but by already existing chronic sinusitis. Immunohistochemical methods are useful for diagnosing olfactory disturbance when used in combination with biopsy of olfactory mucosa.

Molecular cloning of cDNA of S100 alpha subunit mRNA

The primary structure of the bovine S-100 alpha mRNA on the basis of molecular cloning and sequence analysis of the cDNA are described. The sequence is composed of 532 bp which include the 282 bp of the complete coding region, 89 bp at the 5'-noncoding region, 161 bp at the 3'-noncoding region, polyadenylation signal, ATTAAA and poly(A) tail. Northern blot analysis shows that the size of S-100 alpha mRNA is about 700-800 bases long and a single mRNA occurs in bovine brain. Bovine brain contains both S100 alpha and beta subunits and their mRNAs. In contrast, the rat brain contains only S100 beta subunit and its mRNA.

Synthesis of specific brain proteins is influenced by testosterone at mRNA level in the neonatal rat

Sex differences in brain protein synthesis were investigated by analyzing the in vitro translation products of poly (A)+ mRNA isolated from the hypothalamus-preoptic area of male, female and androgenized female (injected with testosterone propionate at day 4) rats at different stages of development. Poly (A)+-enriched mRNA, prepared by oligo (dT)-chromatography of total RNA extracted by guanidine thiocyanate, was translated in either a rabbit reticulocyte lysate or cell-free wheat germ system supplemented with either [35S]methionine or a [3H]amino acid mix. The translation products were analyzed by one- and two-dimensional SDS-PAGE. Several developmental and androgen-induced changes were found in the translation products of specific mRNA species, the most important of which was a sex difference (higher in the male) in the apparent amount of mRNA coding for proteins with the electrophoretic characteristics of actin and tubulin. These developmental and sex differences in the apparent amounts of specific mRNA species in brain may be the cause or result of functional and structural changes such as neurite growth and synapse formation.

Purification and characterization of a neurite extension factor from bovine brain

The extension of neurites by chicken embryo cerebral cortical neurons can be measured quantitatively at low cell density in serum-free, defined medium. An acidic, heat-stable protein fraction from bovine brain has been shown to have neurite extension activity in this assay. We report the use of reversed-phase HPLC to purify a neurite extension factor from this fraction to apparent homogeneity. The protein was characterized by NaDodSO4/PAGE. In the presence of reducing agents, the protein migrated as a single band, with an apparent molecular weight of 6500. In the absence of reducing agents, the protein showed bands at apparent molecular weights of 6500, 21,000-22,000, 30,000, and 40,000. Reduction and S-carboxymethylation of the protein abolished all biological activity and resulted in a shift of the apparent molecular weight to 11,000. The amino acid composition of the purified neurite-extension factor was nearly identical to that of bovine brain S100 beta. The amino acid sequences of peptides derived from trypsin or cyanogen bromide digests of the protein were identical to those found in S100 beta and accounted for 71 of 91 amino acids in the protein. However, three peptides obtained from cyanogen bromide digestion of the nonreduced protein appeared to be disulfide-linked dimers. Our results indicate that a biological activity, neurite extension, which is critical for the development of the nervous system, is associated with a disulfide form of S100 beta.

The developmental changes of mRNA levels for a cerebellar protein (spot 35 protein) in rat brains

Our previous papers described a protein called spot 35 found in the cerebellar cytosol of adult rats by two-dimensional gel electrophoresis and localized in the Purkinje cells by immunohistochemical methods. Here we describe the biosynthesis of this spot 35 protein using a reticulocyte lysate cell-free system containing rat cerebellar mRNA. The developmental changes of mRNA-dependent protein biosynthesis were also examined. During postnatal 10-30 days, a rapid increase of mRNA levels for spot 35 protein was observed. The application of the new 45Ca-binding assay procedure revealed that this protein is a Ca-binding protein.

Immunohistochemical localization of 2',3'-cyclic nucleotide 3'-phosphodiesterase in adult bovine cerebrum and cerebellum

We have previously shown that 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP; EC 3.1.4.37) in rat central nervous tissues can be immunohistochemically stained with anti-bovine CNP serum. However, the anti-bovine CNP serum prepared in our laboratory has only weak cross-reactivity with rat CNP. Sections of bovine nervous tissues were found to be stained effectively with the serum, and the localization of CNP has been revealed in greater detail. We describe here the immunohistochemical localization of CNP in adult bovine cerebrum and cerebellum. CNP stained was localized in myelin sheaths, oligodendrocytes, and the processes of oligodendrocytes; astrocytes and neurons were negative. All myelinated nerve fibers appeared to be stained with the anti-CNP serum. Perineuronal and perivascular oligodendrocytes, and oligodendrocytes extending their processes to isolated myelin fibers were stained. Interfascicular oligodendrocytes, however, did not react or reacted faintly to the anti-CNP serum; only their processes were reactive. Comparison with the stain for S-100 protein was helpful to distinguish oligodendrocytes from astrocytes particularly when both glial cells were situated together at the perineuronal and perivascular positions.

Molecular cloning and the complete nucleotide sequence of cDNA to mRNA for S-100 protein of rat brain

The complete nucleotide sequence of mRNA for beta-subunit of rat brain S-100 protein was determined from recombinant cDNA clones. The sequence was composed of 1488 bp which included the 276 bp of the complete coding region, the 120 bp of the 5'-noncoding region and the 1092 bp of the 3'-noncoding region containing two polyadenylation signals. In addition, the poly(A) tail was also found. The amino acid sequence deduced from the nucleotide sequence was homologous to the amino acid sequence of bovine S-100 beta subunit except 4 residues showing species differences. From the viewpoint of evolutionary implications, the homology between the nucleotide sequence of S-100 and those of rat intestinal Ca-binding protein (ICaBP) and calmodulin (CaM) was examined. A dot-blot hybridization of poly(A) RNA from the developing rat brains using a labeled cDNA showed a rapid increase in S-100 mRNA at 10-20 postnatal days. The presence of S-100 mRNA in C-6 glioma cells is also described.