Involvement of spot 35 protein, a cerebellar protein, in modulation of Purkinje cell activity of the rat cerebellum

Ontogenetic expression of spot 35 protein (calbindin-D28k) in human olfactory receptor neurons and its decrease in Alzheimer's disease patients

Expression of a calcium-binding protein, spot 35 protein (S-35, calbindin-D28k), was investigated immunohistochemically in the human olfactory mucosa of patients who ranged in age from 16 weeks of fetal development to 98 years old, including some with Alzheimer's disease (AD). S-35 immunoreactivity was observed clearly in olfactory receptor neurons (ORNs) and olfactory nerve bundles that were identified previously with antibodies to olfactory marker protein (OMP) and neuron-specific enolase (NSE). Throughout all ages, the mean number of ORNs immunoreactive for OMP did not change significantly, whereas the mean number of NSE- and S-35-immunoreactive ORNs declined markedly in the postnatal infant, young, and old patients when compared with that of the prenatal fetuses. S-35-immunoreactive ORNs decreased significantly in AD patients when compared with AD control patients. These results indicate that ORNs in humans express S-35 and that there is an age-related trend in the expression of S-35. Furthermore, the marked decrease of S-35 expression in ORNs of AD patients suggests that cell excitability associated with calcium ions and cell protective function against overload of intracellular calcium ions decline in these patients.

Cellular distribution of calbindin D28K mRNAs in the adult mouse brain

We have determined the cellular distribution of calbindin D28K mRNAs throughout the mouse brain by in situ hybridization. While these studies identified neuronal populations similar to those previously identified in rat brain by immunohistochemistry, some discrepancies exist. These may derive from species differences or from the immunological cross-reactivity of calbindin D28K antiserum with other proteins. We note an intriguing association between the distribution of neurons containing calbindin D28K mRNA and those reported by others to contain the inositol 1,4,5-triphosphate (InsP3) receptor.

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)

In situ hybridization histochemistry of Spot 35 protein, a calcium-binding protein, in the rat brain

Using in situ hybridization, we analyzed the localization of mRNA for Spot 35 protein (Spot 35), a calcium-binding protein of the EF-hand type, in the rat cerebellum at various developmental stages. A cDNA fragment corresponding to part of the 3'-noncoding region was 35S-labeled and used as a hybridization probe. Autoradiographic signals for Spot 35 mRNA were detected in all the Purkinje cells, but not in any other neurons or glial cells in the adult rat cerebellum. There was no significant difference in signal intensity among individual cells. The signals were observed exclusively in Purkinje cell bodies, but not in their processes, in striking contrast to previous immunohistochemical studies in which Spot 35 protein was demonstrated in both cell bodies and processes. In the time-course study, signals for Spot 35 mRNA were detected in Purkinje cell bodies weakly at embryonic day 19, thereafter more intensely at more developed stages and most intensely at postnatal days 30 and 60 (adulthood). The signal intensities of individual cells were similar at each of these developmental stages except for the very early stages at which signals were weak and slightly variable among cells. These findings, especially that of the characteristic coordinated expression of Spot 35 mRNA at given stages, should prove useful in studies of degenerative diseases in the cerebellum in experimental animals and man. A weak expression of Spot 35 mRNA in some of non-Purkinje cells was also noted.

Gender and gonadectomy influence specific proteins in the cerebellar cortex of the adult rat: a two-dimensional gel electrophoretic analysis

Two-dimensional polyacrylamide gel electrophoresis was used to determine the influence of gender and gonadectomy on individual proteins of the 105,000 g supernatant (cytosol) of the cerebellar cortex of the adult rat. At age 60 days were gonadectomized or sham-gonadectomized. At age 140 days the rats were sacrificed and the 105,000 g supernatant prepared from the cerebellar cortex. Sham-operated female rats were sacrificed during the proestrus stage of the estrous cycle. Out of 200 proteins identified, 13 were influenced by gender and/or gonadectomy. Five of these proteins were influenced by both gender and gonadectomy. A total of 18 differences were observed. Apparent molecular weights and isoelectric points (pIs) for the 13 proteins ranged from 22,000 to 92,000 Da and pH 4.8-6.1, respectively. Sex differences occurred in the percent volumes (spot density) of 9 proteins between intact male and proestrous female rats. Sex differences in 4 proteins were not influenced by gonadectomy. These differences were presumed to be genetically programmed and/or to reflect the permanent organizational effects of gonadal steroids on the genome. Differences in the remaining 5 proteins depend upon the transient activational effects of the testicular sex steroids, i.e. these gender differences were eliminated by castration. The effects of gonadectomy on individual proteins were gender specific, i.e. proteins affected by ovariectomy were not influenced by castration and vice versa. This suggests intact gonads are required for the specific gender-dependent proteins identified in the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)

An immunohistochemical study of the ontogeny of the horizontal cell in the rat retina using an antiserum against spot 35 protein, a novel Purkinje cell-specific protein, as a marker

A sequence of morphological changes during the differentiation of retinal horizontal cells was studied by means of immunohistochemistry for spot 35 protein, a novel Purkinje cell-specific protein, in the rat retina. Spot 35-immunoreactive horizontal cell anlagen were first identified at embryonic day 18 (E18) in the outer zone of the neuroblastic cell layer as fusiform cells with slender inner and outer processes. As the development proceeded, the immunoreactive cells increased in number and intensity of the immunostaining, and the outer processes of the immunoreactive cells were often bifurcated close to their origin or at their periphery. At postnatal days 3 and 5 (P3 and P5), a regional difference in morphology of the immunoreactive horizontal cell anlagen was recognized: The immunoreactive cells near the ora serrata still assumed a bipolar shape, and those in the central portion of the retina had multiple processes. At P7 and P10, the immunoreactive cells in the periphery of the retina extended most of their outer processes in the plane of the retina, forming a network together with processes of adjacent immunoreactive horizontal cells. Their internally extending processes during these postnatal stages tended to be present in small numbers and to be short. At P14 all the immunoreactive horizontal cells extended their processes horizontally to form a tight bundle all the way along the outer plexiform layer. These findings indicate that spot 35 protein is a specific marker for the horizontal cells of the rat retina in the developmental process from their bipolar stage at E18 until reaching their mature configuration at P14.

Heterogeneity of the ciliary epithelium of the rat eye as revealed by spot 35 protein (a Purkinje cell specific protein)-like immunoreactivity

By means of immunoreactivity for spot 35 protein, a novel cerebellar Purkinje cell-specific protein, the regional heterogeneity among non-pigmented ciliary epithelial cells of rats was demonstrated with reference to the antero-posterior and crest-valley directions of individual ciliary epithelial folds in immature and mature eyes. The functional significance of the occurrence of the spot 35 immunoreactivity in the posterior portion of the ciliary epithelium is briefly discussed in relation to the formation of the aqueous humor.

Developmental and regional changes of mRNA for a cerebellar protein (spot 35) in the rat brain

Spot 35 protein is a cerebellar Ca-binding protein. Because Southern blot analysis showed evidence for the nucleotide sequence of spot 35 protein cDNA in the rat genome, we applied cDNA to quantitate the mRNA of rat spot 35 protein. The size of this mRNA was about 1,900 nucleotides in length, and that of mRNA from bovine cerebellum was larger. We also examined the developmental changes and regional distribution of spot 35 protein mRNA in rat brains by dot-blot analysis using cDNA as a probe. During postnatal days 1-20, a rapid increase of mRNA levels was observed. Further, the level of mRNA for spot 35 protein was found in the cerebellum and was negligible in the cerebral cortex, striatum, and hippocampus.

Molecular cloning of cDNA to mRNA for a cerebellar spot 35 protein

The nucleotide sequence of mRNA for rat cerebellar spot 35 protein, a Ca-binding protein, was determined from recombinant complementary DNA (cDNA) clones. The sequence was composed of 1,714 base pairs (bp) which included the 783 bp of the complete coding region, the 130 bp of the 5'-noncoding region, and the 801 bp of the 3'-noncoding region containing a polyadenylation signal. In addition, a polyadenylic acid [poly(A)] tail was also found. Because the size of spot 35 mRNA was estimated to be about 1,900 bases by Northern blot analysis, the longest insert was verified to contain a nearly full-length cDNA sequence including the poly(A) tail. The amino acid sequence of the protein deduced from the nucleotide sequence contains 261 amino acids and at least five Ca-binding domains. There was a high homology in the amino acid sequences (79%) and the nucleotide sequences (77%) between spot 35 protein and chick intestinal Ca-binding protein (28K).

An immunohistochemical study on the ontogeny of cells immunoreactive for spot 35 protein, a novel Purkinje cell-specific protein, in the rat cerebellum

A time course study on the appearance and distribution of cells immunoreactive for spot 35 protein, a novel cerebellar Purkinje cell-specific protein, was conducted in the developing cerebella of fetal and early postnatal rats by PAP immunohistochemistry. Spot 35-immunoreactive cells were first noted in the cerebellar anlage on the 17th embryonic day, appearing as large cellular aggregations in the mantle layer and a small number of elongated cells dispersed between the cell aggregations and the ependymal layer. As the development proceeded, the spot 35-immunoreactive cells gradually accumulated beneath the external granular layer. At birth, they were arranged compactly in 4-5 irregular rows to form a primitive Purkinje cell layer. During their subsequent development, immunostaining for spot 35 protein demonstrated the rearrangement of the Purkinje cells into a single row and the maturation of their somata, axons and dendrites. All these findings indicate that spot 35 protein is a specific marker for the cerebellar Purkinje cells, from their migrating stage throughout the course of their maturation. The present study further describes the transitory lamellar arrangement of spot 35-immunoreactive Purkinje cells located horizontally at a short distance away from the ependymal layer of the cerebellum on the 17th embryonic day.

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.