Calcium-binding protein (28,000 Mr calbindin-D28k) in kidneys of the bullfrog Rana catesbeiana during metamorphosis

Calbindin Has a Potential Spatiotemporal Correlation with Proliferation and Apoptosis in the Postnatal Rat Kidney

The protein calbindin-D28k modulates calcium reabsorption in the kidney. Here, we aimed to study the influence of proliferation and apoptosis in different compartments of the kidney on the developmental function of calbindin. Using immunohistochemistry, we investigated the postnatal development of rats' kidneys by using calbindin, proliferative cell nuclear antigen (PCNA), and apoptotic single-stranded DNA (ssDNA). In the neonatal stage (1-day and 1-week-old rats), calbindin showed a positive reaction in the distal convoluted tubule (DCT), a short nephron segment between the macula densa, collecting ducts, and tubules. Moreover, the localization of calbindin was restricted to immature nephrons and mesenchymal tissues. Furthermore, PCNA immunoreactivity was moderate in early-developed podocytes with no reactivity in other renal tubules. The ssDNA immunoreactivity was moderate in the undifferentiated nephron. Then, in the mature stage (3 and 6 weeks old), there was an intense calbindin reaction in DCT but a moderate reaction to PCNA and ssDNA in podocytes. A more intense calbindin reactivity was found in the adult stage (2- and 3-month-old rats) in DCT and collecting tubules. Therefore, in this study, calbindin localization showed an inverse relationship with PCNA and ssDNA of the nephron compartments, which might reflect the efficiency of bone-building and muscle contraction during animal development.

Histological and Immunohistochemical Investigation of the Cerebellum in Porcupine and Guinea Pig

The present study was designed to investigate the cerebellum histology and immunohistochemistry in porcupine (Hystrix cristata) and guinea pig (Cavia porcellus). Two adult porcupines and two adult guinea pigs were used. For general histology, crystal violet and Luxol fast blue stains were applied. For immunohistochemistry, myelin-associated glycoprotein (MAG), neurofilament 200 (NF200), calbindin D-28K, and glial fibrillary-associated protein (GFAP) were investigated. The cerebellar cortex in both species was composed of three cellular layers: molecular, granular, and Purkinje cell (PC) layers. Purkinje cells in the porcupine showed a purple-colored and dark blue-colored cytoplasm in reaction to the crystal violet and Luxol fast blue staining, respectively. In the guinea pig, PC has a uniform reaction to the Luxol fast blue with dark-blue-colored cytoplasm. However, in response to the crystal violet, some PC with dark-purple cytoplasm showed stronger reaction than other PC which showed light-purple cytoplasm. The PC layer in some folia of the porcupine cerebellum was composed of 2-3 layers. The expression rates of calbindin D-28K, MAG, GFAP, and NF200 in the porcupine cerebellum were determined to be 19%, 42.5%, 62%, and 30%, respectively. These values were determined to be 27%, 34%, 43.5%, and 31.5%, respectively, in the guinea pig cerebellum.

Role of Clast1 in development of cerebellar granule cells

We have identified the murine Clast1/LR8 gene by subtraction of cDNA derived from CD40 ligand-activated and naive B cells. The Clast1 gene is ubiquitously expressed in various organs of adult mice. However, its physiological function was largely unknown. To study a role of Clast1, we established Clast1-deficient (Clast1-KO) mice. Here, we reveal that approximately 65% of Clast1-KO mice showed severe ataxia. The Clast1-KO cerebellum with ataxia is small in size and revealed a severely aberrant lobulation, loss of the internal granule cell layer, and the disorganized Purkinje cells. Clast1 mRNA is expressed in the cerebellar granule cells of normal adult mice. Developmentally, Clast1 mRNA is also detected in the external germinal layer of the embryonic cerebellum, indicating its expression in granule cell precursors. Histopathological analysis of the developing Clast1-KO cerebellum demonstrated the reduced number of cells in the external germinal layer. Thus, Clast1 is required for development of cerebellar granule cells.

Occurrence and localization of calbindin-D28K in kidney and cerebellum of the slider turtle, Trachemys scripta

BACKGROUND

Since its initial discovery in the avian intestine, calbindin-D28K has been reported to occur in various species and tissues. Although calbindin-D28K binds calcium ions in the physiologically relevant range of intracellular calcium, its functional role in the various cell types where it has been localized remains unknown.

METHODS

We examined the occurrence of calbindin-D28K in the brain and kidney of the testudine reptile, Trachemys scripta, by immunoblotting and immunocytochemistry using rabbit anti-sera directed against rat renal calbindin-D28K and chicken intestinal calbindin-D28K.

RESULTS

Immunoblotting revealed the presence of calbindin-D28K in the turtle tissues. A single immunoreactive band in the 28,000 relative molecular mass region was visualized in cerebellar and renal homogenates. Immunocytochemistry revealed reaction product for the presence of calbindin-D28K in the Purkinje cells of the cerebellum, and in the distal tubular cells of the nephron. Processes as well as the perikaryon of the Purkinje cell were immunoreactive.

CONCLUSION

This study describes the occurrence and cellular localization of calbindin-D28K in a reptilian cerebellum, and confirms the phylogenetic distribution of renal calbindin-D28K to the oldest major reptilian group.

The 9-kDa calbindin gene of Rousettus aegyptiacus: its identification and isolation from a genomic library

A genomic library of the fruit bat (Rousettus aegyptiacus) was constructed in lambda phage gt11. The titre of the library was determined to be 2 x 10(5) pfu/ml. The genomic library was amplified and the titre of the amplified library increased 300-fold to 7 x 10(7) pfu/ml. The library was screened by in situ hybridization techniques using a fragment of the mouse 9-kDa calbindin cDNA as a probe. Screening of 10(5) plaques yielded a positive clone. Three additional rounds of screening were performed to purify the positive. Lambda phage DNA was isolated from the positive clone and restriction digest analysis, followed by hybridization studies, was performed on these digests in order to determine the location of the bat 9-kDa calbindin gene in the insert of the lambda phage vector. Restriction maps so derived were interpreted from the published sequence for the rat 9-kDa calbindin gene and indicate the successful isolation of the 9-kDa calbindin gene of Rousettus aegyptiacus.

Detection of the 9-kDa vitamin D-dependent calbindin gene in a fruit bat (Rousettus aegyptiacus) fibroblast cell line

1. A fibroblast cell line was established from skin and lung tissue of the fruit bat (Rousettus aegyptiacus). 2. Genomic DNA, isolated from the fibroblast cells, was restriction digested and probed for the 9-kDa calbindin gene with a 180 base-pair fragment of mouse calbindin-D9K cDNA. Genomic DNA from rats and humans was similarly probed. 3. Hybridization and thus homology was observed between the mouse probe and DNA from the rat and the fruit bat, but not the human. 4. The results are discussed in relation to the detection of calbindin-D9K in the fruit bat despite very low circulating levels of its inducer 1,25(OH)2D3.

Immunohistochemical localization of calbindins (28K and 9K) in the tissues of the baboon Papio ursinus

An indirect immunoperoxidase procedure was used to detect the presence of calbindin-D28K and calbindin-D9K in the cerebellum, kidney, and duodenum of the baboon Papio ursinus. Antibodies to chick calbinding-D28K and to both rat and mouse calbindin-D9K were used. The cerebellum and kidney were shown to contain calbindin-D28K; the doudenum contained calbindin-D9K. In the cerebellum, positive staining was found in the Purkinje cells only; in the kidney, positive staining was found in the distal convoluted tubules, connecting tubules, and collecting tubules, extending deep into the medullary regions of the kidney. Staining in the duodenum was confined to the enterocytes of the villi, with no stain present in the crypt regions or goblet cells. Thus the baboon, a primate, contains the larger of the calbindins in both the cerebellum and kidney as does the human and monkey, but its distribution in the kidney is more generalized than that found in humans. The molecular weight of calbindin-D9K was found to be similar to that found in other animals. However, the calbindin-D28K from the baboon tissues appears to be slightly smaller than the protein found in other animals and may therefore be of similar size to the human calbindin-D28K (Mr 26,000).

Cellular gene expression for calbindin-D28k in mouse kidney

Gene expression for calbindin-D28k, the 28,000 relative molecular mass vitamin D-dependent calcium-binding protein, was measured in cells of the murine nephron by in situ hybridization on tissue sections (hybridization cytochemistry). Radiolabeled (35S-UTP), single-stranded RNA complementary to calbindin-D28k-mRNA (probe RNA) was prepared from linearized cDNA template and used for the hybridizations. Autoradiography was carried out and cellular levels of hybridization signal (silver grains) were quantified. After correction for background the concentration of silver grains was more than 350% greater in the distal tubule than in either the proximal tubule or the glomerulus. The relative cellular level of mRNA in the cytoplasm, as reflected in silver grains/cell, of the distal tubules with probe RNA was 3.4 times greater than that with control RNA. Cells of the distal tubule were the only apparent sites of specific hybridization with probe RNA. The presence of calbindin-D28k-mRNA in the distal tubule corresponded to the localization of calbindin-D28k by immunocytochemistry.

Molecular cloning of mammalian 28,000 Mr vitamin D-dependent calcium binding protein (calbindin-D28K): expression of calbindin-D28K RNAs in rodent brain and kidney

We report the isolation of a cloned cDNA for the mammalian 28,000 Mr vitamin D-dependent calcium binding protein (calbindin-D28K; CaBP28K) by immunological screening of a lambda gt11 bacterial expression library. The library contained cDNAs copied from poly(A)RNA of adult mouse cerebellum. We confirmed the identity of the CaBP28K cDNA by comparing its DNA sequence with that of chick CaBP28K cDNA. In the coding region, 79% of the mouse cDNA sequence was identical to the reported sequence of CaBP28K cDNA derived from chicken intestine. Rat brain and kidney each contain three species of poly(A)RNA that hybridize to CaBP28K cDNA--a major species of 1.9 kb, and rarer components of 2.8 kb and 3.2 kb. All three RNAs appear to be transcribed from a single gene. The ratios of these CaBP28K RNAs were the same in brain and kidney. In the cerebellum, in situ hybridization reveals that CaBP28K RNAs are confined to Purkinje neurons.

A quantitative immunobinding assay for vitamin D-dependent calcium-binding protein (calbindin-D28k) using nitrocellulose filters

A sensitive dot immunobinding assay has been developed for the quantitative determination of vitamin D-dependent calcium-binding protein (calbindin-D28k; CaBP) in rat and human kidney and brain. Protein samples are spotted onto nitrocellulose sheets, fixed, and then rinsed with Tris-buffered saline. The remaining protein binding sites are blocked with bovine serum albumin, gelatin, or nonfat dry milk protein and the filters are then incubated sequentially with antiserum to calbindin-D28k (1:500 dilution) and 125I-protein A (200,000 cpm/ml). After washing, the radioactivity bound to each sample is quantitated by counting in a gamma counter. The sensitivity of the assay is such that 10 ng calbindin-D28k can be accurately quantitated. The highest levels of CaBP were detected in kidney (7.8 +/- 0.5 micrograms/mg protein) and cerebellum (22.1 +/- 1.4 micrograms/mg protein). Ten micrograms calmodulin, lactalbumin, or parvalbumin and 100 micrograms liver extract showed no reactivity in the assay. The assay is precise (intraassay variability, 4.0%) and reproducible (interassay variability, 8.8%). There was good agreement between the data in this assay and the data we obtained using radioimmunoassay (RIA). The assay has several advantages over the RIA. Iodination of pure antigen is not required and it is possible to detect membrane-bound and insoluble antigens using this assay. Also, the antiserum and 125I-protein A solutions can be saved and reused. This assay represents a major modification of the original immunobinding assays which used the less sensitive peroxidase stain. It is also an improvement over previous 125I immunobinding assays which were not quantitative but were used as antigen "spot tests" or which required iodination of the antibody.