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Calbindin-D9k gene expression in the uterus: study of the two messenger ribonucleic acid species and analysis of an imperfect estrogen-responsive element.

The calbindin D9k (CaBP9k) gene is under strict estrogen control in the rat uterus. This tissue contains two CaBP9k messenger RNA (mRNA) species. We have used primer extension analysis, reverse transcriptase associated with polymerase chain reaction, and RNase H digestion to show that these two mRNA species have the same structural features, including 5'- and 3'-ends, and poly(A) tail length. Our results suggest that the difference in electrophoretic mobilities of the two mRNA species might be due to interaction with another factor. We also analyzed the imperfect estrogen-responsive element (ERE) present on the first 5'-splice site of the rat CaBP9k gene. The oligonucleotide corresponding to the CaBP9k ERE was cloned in the plasmid pBLCAT2 (where the thymidine kinase promoter governs the expression of the chloramphenicol acetyl transferase gene) and transfected into MCF7 cells. This CaBP9k ERE was found to be a hormone-inducible enhancer that worked in an orientation-independent manner on a heterologous promoter and was functional at physiological hormone concentrations. One CaBP9k ERE conferred only weak (about 2-fold) estrogen induction, but two EREs cloned in tandem were strongly synergistic (14- to 16-fold). The CaBP9k ERE also bound to the partially purified estrogen receptor (ER) and to ER expressed in COS cells by gel shift assay. Methylation interference showed that all the guanine residues in both half-sites of the CaBP9k ERE were protected by ER binding. Thus, ER binds to the CaBP9k ERE in a way similar to other EREs. The gel shift assay results indicate that the strong synergistic effect of two EREs cloned in tandem is not due to cooperative binding between the two elements. As the CaBP9k gene is under strong estrogenic control in the uterus in vivo, the imperfect CaBP9k ERE may cooperate with another trans-acting factor to become fully efficient.

Animals↗

Transgenic analysis of the response of the rat calbindin-D 9k gene to vitamin D.

The promoter of the calbindin-D 9k (CaBP9k) gene, previously analyzed in transgenic mice, contains all of the information necessary for expression of a transgene similar to the endogenous gene and also for an appropriate response to vitamin D. In the present study we first investigated the role of a putative vitamin D-responsive element (9k/VDRE), located at nucleotides -489 to -445 on the rat CaBP9k promoter gene, using transgenic mice. As expected, the pattern of transgene expression in mice carrying this putative VDRE mutated in its whole promoter context was similar to that in mice bearing the wild-type sequence. These transgenic mice also responded to 1,25-dihydroxyvitamin D3 in the same way as those bearing the wild-type transgene and as those carrying a transgene with a large deletion (from -2894 to -117) eliminating the putative 9k/VDRE. Thus, the putative 9k/VDRE is not required for the control of rat CaBP9k gene expression by vitamin D in vivo. We also found that responsiveness to 1,25-dihydroxyvitamin D3 depends on the site at which the transgene is integrated into the host genome, in a tissue-specific manner. These data together with the fact that vitamin D-responsive sequences are present in a two-module region (from -3731 to -2894 and/or -117 to +365) and that this region does not contain any classical VDRE show that the CaBP9k gene is submitted to a non-conventional control by vitamin D.

Animals↗

Conflict of estrogenic activity by various phthalates between in vitro and in vivo models related to the expression of Calbindin-D9k.

Phthalates are suspected to disrupt the endocrine system, especially through estrogenic effects. In the present study, we investigated the effects of various phthalates and compared them with those of estrogenic compounds that disrupt the female reproductive system. To assess the effects of these phthalates, alteration of the Calbindin-D9k (CaBP-9k) gene was measured as a biomarker because rat CaBP-9k gene carries an estrogen response element (ERE) which is involved in estrogen responsiveness of the gene during the estrous cycle. In this study, phthalates were tested for estrogenic properties in in vitro and in vivo models. First, the E-Screen assay was used to measure the proliferation of MCF-7 cells, a human breast cancer cell line. Treatments with 17beta-estradiol (E2; 9-fold) and 17alpha-estradiol (EE; 9-fold) induced MCF-7 cell proliferation at concentrations of 10(-9) M. Phthalates induced an increase in MCF-7 proliferation at concentration of 10(-6) M up to 10(-4) M. Nbutyl benzyl phthalate (BBP; 6-fold vs. vehicle), dicyclohexyl phthalate (DCHP; 8-fold), 2-ethylhexyl phthalate (DEHP; 6-fold) and di-n-butyl phthalate (DBP; 7-fold) at the concentration of 10(-4) M induced in an increase in MCF-7 proliferation after 6 d of treatment compared to vehicle. However, significant increase in MCF-7 proliferation was induced by diethyl phthalate (DEP). Second, we investigated the expression of CaBP-9k in the uterus of immature rats after oral treatment with BBP, DCHP, DEHP, DBP or DBP (600 mg/kg per day) in this in vivo model, because the immature rat model is highly sensitive to exposure to estrogenic chemicals. None of the phthalates induced the expression of CaBP-9k mRNA and its protein in the neonatal uterus as analysed by Northern and Western blot analyses, respectively. Although phthalates induced an increase in MCF-7 cell proliferation by an estrogenic effect, they could not induce CaBP-9k expression in the in vivo system, suggesting that the assays of estrogenic effects of various phthalates conducted in vitro and in vivo expression of CaBP-9k may produce conflicting results.

Animals↗

Maternal exposure to bisphenol a during late pregnancy resulted in an increase of Calbindin-D9k mRNA and protein in maternal and postnatal rat uteri.

It has been reported that Calbindin-D9k (CaBP-9k) is rapidly and strongly induced by environmental estrogenic compounds, possibly through estrogen receptors (ERalpha) in the uterus of mammals. CaBP-9k can be evaluated as an early gene marker for assaying estrogenic effects of putative environmental chemicals in the rat uterus. This study was undertaken to investigate CaBP-9k mRNA and protein expression in the postnatal rat uterus following maternal exposure to 17beta-estradiol (E2) and bisphenol A (BPA) during the neonatal period. Treatment with a high dose of BPA (600 mg/kg body weight (BW) per day) resulted in a 3-fold increase in CaBP-9k mRNA expression for 3 days, while a single dose of E2 (40 microg/kg BW per day) induced 2-fold increase of this gene in the maternal uterus. In an agreement with maternal CaBP-9k mRNA, postnatal CaBP-9k mRNA in the uterus increased 4-fold when treated with BPA (600 mg/kg BW per day). In addition, treatment with increasing concentrations of BPA resulted in significant increases in CaBP-9k protein in the maternal rat uterus. It is of interest that increasing doses of BPA induced a significant ERalpha mRNA increase in the postnatal uterus. Furthermore, immunohistochemistry revealed that treatment with BPA induced CaBP-9k protein in the maternal uterus. We demonstrated that maternal exposure to BPA during late pregnancy induced CaBP-9k mRNA and protein in maternal and postnatal rat uteri. These results suggest that rapid absorption and distribution of environmental estrogenic compounds occurs in maternal and neonatal rat uteri and these chemicals can easily pass though the placenta during pregnancy to affect postnatal reproductive functions.

Animals↗

Calbindin-D9k mRNA expression in the rat uterus following exposure to methoxychlor: a comparison of oral and subcutaneous exposure.

Calbindin-D(9k) (CaBP-9k) is a cytosolic calcium-binding protein that is induced by estrogenic compounds possibly through estrogen receptors. We compared CaBP-9k mRNA expression in the uterus with uterotrophic response in immature rats exposed to methoxychlor (MC), an environmental chemical with estrogenic activity. MC was orally or subcutaneously administered to 3-week-old female Sprague-Dawley rats for 3 days. The weights of the uterus and vagina significantly increased in the oral treatment group at a dose of 50, 100 and 200 mg/kg, but those of the subcutaneous (SC) treatment group only increased at 200 mg/kg. Northern blot analysis showed that CaBP-9k mRNA expression was significantly induced in a dose-dependent manner at doses of 50, 100 and 200 mg/kg/day in the oral treatment group. SC administration of MC induced significant expression at only a dose of 200 mg/kg/day; this was similar to the uterotrophic response. MC has an estrogenic effect on the uterus as shown by the increase in weight and induction of CaBP-9k mRNA expression, which were much greater following exposure via oral gavage than via the SC route. The strong correlation between the results of in vivo uterotrophic assay and CaBP-9k mRNA expression suggests that CaBP-9k mRNA expression in the rat uterus may be used as an early gene marker for detection of the estrogenic effects of putative environmental chemicals.

Administration, Oral↗

Differential transcriptional and translational regulations of calbindin-D9k by steroid hormones and their receptors in the uterus of immature mice.

Calbindin-D(9k) (CaBP-9k) is a cytosolic calcium binding protein mainly expressed in the duodenum, placenta and uterus, and intestinal CaBP-9k is regulated by 1, 25-dyhydroxyvitamin D3. However, despite the presence of vitamin D receptors, uterine CaBP-9k is not under the control of vitamin D, but seems to be regulated by sex steroids. This steroids-dependent regulation of CaBP-9k is not only limited to a tissue-specific manner but also extends to a species-specific manner. In this study, we examined the regulation of CaBP-9k gene at the transcriptional and translational levels, and also localized CaBP-9k protein in the uterus of immature mice. Treatment with progesterone (P4) resulted in the induction of CaBP-9k mRNA, and a co-treatment with estrogen (E2) plus P4 evoked a synergic effect on its mRNA level in this tissue. Interestingly, the translation of CaBP-9k protein was enhanced by E2, while no difference was observed at the transcriptional level. Not only P4 but also E2 itself induced an increase of CaBP-9k protein, and co-treatment with E2 and P4 showed a similar effect on its protein level in the uterus of immature mice. The CaBP-9k protein was localized in the glandular epithelium of stroma in the uterus of immature mice at diestrus, indicating that the expression of CaBP-9k protein is differentially regulated by sex steroids. A potential mechanism of synergic effect of P4 and E2 may be E2 action in the increase of progesterone receptor (PR), with up-regulated PR increasing P4-induced CaBP-9k expression. This complicated relationship between CaBP-9k and steroid receptors suggests that P4 regulates CaBP-9k gene in the uterus of immature mice, in addition, E2 also can affect the expression of CaBP-9k through the regulation of PR. The expression levels of ERalpha and PR were further examined in this tissue. E2 stimulated the expression levels of ERalpha and PR mRNAs and P4 inhibited the expression of these transcripts at an early time point (12 h) and increased them at 24 and 48 h, while co-treatments with both steroids increased transcripts of ERalpha and PR at 24 h. In conclusion, P4 and PR may be dominant factors in the regulation of CaBP-9k. Also, E2 and ERalpha can influence the expression of the CaBP-9k gene via an indirect pathway in the uterus of immature mice.

Age Factors↗

Chronic hypoxia alters calbindin D-28k immunoreactivity in lingual and laryngeal taste buds in the rat.

The distribution and abundance of the calcium binding protein, calbindin D-28k (CB) immunoreactivity in the taste buds of the circumvallate papillae and larynx were compared between normoxic and chronically hypoxic rats (10% O2 for 8 weeks). In the normoxic rats, CB immunoreactivity was observed in some cells and fibers of the intragemmal region of the taste buds in the circumvallate papillae. In contrast, in the subgemmal region of the laryngeal taste buds, fibers but not cells were immunoreactive for CB. In chronically hypoxic rats, CB immunoreactive cells and fibers in the taste buds were decreased in the circumvallate papillae. In the laryngeal taste buds, the density of the subgemmal CB immunoreactive fibers in chronically hypoxic rats was greater than in normoxic rats. It is considered that function of the laryngeal taste buds is different from that of the lingual taste buds, so that laryngeal taste buds may be involved in chemosensation other than taste. The altered density of CB immunoreactive cells and fibers in the lingual and laryngeal taste buds is a predominant feature of hypoxic adaptation, and chronic hypoxic exposure might change the chemical sensitivity of the circumvallate papillae and larynx through the regulation of intracellular Ca2+.

Adaptation, Physiological↗

Expression of calbindin-D28K in sporadic nephroblastomas of the chicken.

Calbindin-D28K (Ca-D28K) is a calcium-binding protein. In the kidney, Ca-D28K is present in the distal nephron, but not in the proximal nephron. This site-specific distribution in the kidney indicates that Ca-D28K is a potential marker for the differentiation of the distal nephron. In this study, we have examined the expression of Ca-D28K in 25 sporadic cases of chicken nephroblastomas. All cases of nephroblastomas were composed of atypical tubular structures, blastemal cells, and fibrous stroma in varying degrees of differentiation. Immunohistochemically in all nephroblastoma specimens, Ca-D28K was expressed in the epithelial cells of the subsets of tubular structures, but not in the blastema or the stroma. These results suggested that the tubuli in the nephroblastomas are able to differentiate into the phenotype of distal nephrons. Furthermore, Ca-D28K might develop as a novel diagnostic marker for nephroblastomas because this molecule is reported to be completely negative in other renal tumors, including renal cell carcinoma, chromophobe carcinomas, and oncocytoma.

Animals↗

An immunocytochemical study of calbindin-D28K in laminae I and II of the dorsal horn and spinal ganglia in the chicken with special reference to the relation to substance P-containing primary afferent neurons.

The localization of calbindin-D28K (CB) was studied immunocytochemically in laminae I and II of the dorsal horn and in spinal ganglia in the chicken, and compared with the distribution of substance P (SP) using double immunolabeling. At the light microscopic level, CB immunoreactivity was observed most intensely in the lamina II using the avidin-biotinylated peroxidase complex (ABC) and immunofluorescence methods. At the electron microscopic level using the ABC method, CB immunoreactivity was observed in the following three neuronal elements: 1) the scalloped central terminal with many dense-cored vesicles (DCVs) in the synaptic glomerulus; 2) some vesicle-containing dendrites (VCDs) inside or outside the synaptic glomerulus; and 3) some axon terminals outside the synaptic glomerulus. The CB-immunoreactive (IR) VCDs in the synaptic glomerulus often formed reciprocal synapses with the central terminal. Strong immunoreactivity was observed at the postsynaptic membrane of CB-IR elements. Double immunofluorescence and immunolabeling methods at the electron microscopic level showed that CB and SP colocalized in the scalloped central terminal with DCVs of the synaptic glomerulus. Almost all SP-IR neurons in the spinal ganglion revealed the coexistence of CB in serial sections in the chicken. In light of previous biochemical and physiological reports, our findings suggest that CB - coexisting with SP - plays an important role in the control of pain transmission through its strong Ca(2+)-buffering action in the chicken.

Animals↗

Effects of monocular enucleation on calbindin-D 28k and c-Fos expression in the lateral geniculate nucleus in rats.

The present study was undertaken to evaluate the effects of monocular enucleation on the calbindin-D 28k (CB) and c-Fos immunoreactive (IR) neurons in the lateral geniculate nucleus (LGN) complex of adult rats. The enucleation resulted in neuronal degeneration and decrease of neurons in the LGN complex. Our study demonstrated a decrease of CB-IR neuronal density on the contralateral side of the ventral (vLGN) and dorsal LGN (dLGN) until 12 weeks post-enucleation (PE). On the ipsilateral side, CB-IR neuronal density in the dLGN and vLGN showed significant and continuous decrease until 48 and 12 weeks PE, respectively. In an additional experiment, c-Fos-IR neurons were increased at 2 days PE in the vLGN with ipsilateral predominance. At 7 days, c-Fos-IR neurons on the ipsilateral vLGN were still higher than those of pre-enucleated rats. The present results suggest that monocular enucleation affects the expression of the CB and c-Fos in the LGN complex. It is indicated that these may play an important role in the neuronal degeneration and neuroplasticity of the subvisual system in rats.

Animals↗

The specific expression patterns of lactase, sucrase and calbindin-D9k in weaning rats are regulated at the transcriptional level.

During weaning, rat lactase-phlorizin hydrolase (LPH) expression decreased to the low levels found in adults, while sucrase-isomaltase (SI) sharply increased. Calbindin-D9k (CaBP) is specific to the intestine and expression peaked within a few days of weaning. The present study investigates whether these molecules are regulated at transcriptional or post-transcriptional levels and examines the effects of diet on regulation. At normal weaning on day 21, litters were separated from their dams and one group was fed with a standard laboratory diet (weaned (W) group). The other group received a diet containing lactose as the sole source of carbohydrate (lactose-fed (L) group). Mucosal cells were obtained from the proximal part of the rat small intestine and then the activity and concentration of LPH, SI and CaBP proteins and mRNAs were determined. Three parameters revealed the same changing patterns in LPH, SI and CaBP during development and there was significant (p<0.001) correlation between three parameters: LPH, r=0.97 for activity vs. protein, r=0.99 for activity vs. mRNA, r=0.96 for protein vs. mRNA, SI, r=0.99 for activity vs. protein, r=0.98 for activity vs. mRNA, r=0.96 for protein vs. mRNA, CaBP, r=0.94 for activity vs. protein, r=0.97 for activity vs. mRNA, r=0.95 for protein vs. mRNA. Expression of the three proteins did not differ between the L and W groups. Accordingly, it has been suggested that the expression of LPH, SI and CaBP during development is defined at the transcriptional level and dietary changes do not exert a primary effect on it.

Aging↗

The effects of calbindin D-28K and parvalbumin antisense oligonucleotides on the survival of cultured Purkinje cells.

The role of calcium binding proteins, calbindin D-28k (CaB) and parvalbumin (PV) in Purkinje cell survival was investigated using oligonucleotide antisense strategy. Purkinje cell enriched cultures were prepared from the cerebella of 0-1 day old Balb/c mouse pups. Purkinje cells were identified by size, asymmetric arbors, immunoreactivity to CaB and PV, uptake of gamma-aminobutyric acid (GABA) and failure to express glial fibrillary acidic protein. The cells at different days in vitro were treated with antisense or mismatched antisense phosphorothioate oligonucleotides for CaB and PV mRNA (complexed with lipofectin). Neuronal specific [3H]-GABA uptake was used as a measure of Purkinje cell survival. The cultures treated for 24 h with antisense oligos (CaB+PV) showed a significant decrease in [3H]-GABA uptake as compared with the cultures treated with lipofectin alone or with lipofectin + mismatched antisense oligos to CaB and PV mRNA. The results of the present study suggest that the expression of calcium buffering proteins CaB and PV may have a significant involvement in Purkinje cell viability.

Animals↗

Surviving granule cells of the sclerotic human hippocampus have reduced Ca(2+) influx because of a loss of calbindin-D(28k) in temporal lobe epilepsy.

In mesial temporal lobe epilepsy (mTLE), the predominant form of epilepsy in adults, and in animal models of the disease, there is a conspicuous loss of the intracellular Ca(2+)-binding protein calbindin-D(28k) (CB) from granule cells (GCs) of the dentate gyrus. The role of this protein in nerve cell function is controversial, but here we provide evidence for its role in controlling Ca(2+) influx into human neurons. In patients with Ammon's horn sclerosis (AHS), the loss of CB from GCs markedly increased the Ca(2+)-dependent inactivation of voltage-dependent Ca(2+) currents (I(Ca)), thereby diminishing Ca(2+) influx during repetitive neuronal firing. Introducing purified CB into GCs restored Ca(2+) current inactivation to levels observed in cells with normal CB content harvested from mTLE patients without AHS. Our data are consistent with the possibility of neuroprotection secondary to the CB loss. By limiting Ca(2+) influx through an enhanced Ca(2+)-dependent inactivation of voltage-dependent Ca(2+) channels during prolonged neuronal discharges, the loss of CB may contribute to the resistance of surviving human granule cells in AHS.

Action Potentials↗

[Calbindin D-28k-containing neurons receiving visceral and somatic nociceptive information in interstitial nucleus of the spinal trigeminal tract project to the parabrachial nuclei in the rat].

The calbindin D-28k (CB)-containing neurons in the interstitial nucleus of the spinal trigeminal tract (INV) that receive visceral and orofacial somatic nociceptive information and emanate projections to the parabrachial nuclei (PB) were investigated by the triple-labeled methods of fluorogold (FG) retrograde tracing combined with Fos and CB proteins immunofluorescence histochemistry in the rat. The results showed (1) in the perioral stimulation group, a large number of FG-retrograde labeled and Fos-immunoreactive neurons were found in the paratrigeminal nucleus (PaV) and the dorsal paramarginal nucleus (PaMd) of the INV ipsilateral to FG and formalin injection made to the PB and lips, respectively, while a lot of CB-immunoreactive neurons were distributed in the INV bilaterally; (2) a majority of the FG-retrograde labeled neurons (77.3%) were double-labeled with CB, and 40.7% of them were double-labeled with Fos; about 38.5% of FG/CB double-labeled neurons were FG/CB/Fos triple-labeled in the INV; and (3) in the upper alimentary tract stimulation group, the distribution and the numbers of FG-retrograde labeled, CB-immunoreactive neurons and FG/CB double-labeled neurons in the INV were similar to those of the perioral stimulation group as described above, except that the Fos immunoreactive neurons were distributed in the INV bilaterally, approximately 41.9% of the FG-retrograde labeled neurons were FG/Fos double-labeled, and over half (52.0%) of those double-labeled neurons were FG/CB/Fos triple-labeled. The results indicate that a part of CB-containing neurons in the INV receive orofacial somatic and visceral nociceptive information and that these neurons sent projections directly to the PB. The CB-containing neurons might play an important role in the transmission of the peripheral nociceptive information from INV to PB.

Animals↗

Calbindin D-28K in the nucleus pretectalis superficialis parvicellularis of Salmo gairdneri: an immunocytochemical study.

The distribution of calbindin D-28K (CaBP28K) cell bodies and fibers in the nucleus pretectalis superficialis parvicellularis of the rainbow trout was studied using a monoclonal antibody and the avidin-biotin-peroxidase method. In this diencephalic nucleus a very high density of CaBP28K immunoreactive fibers was found. In addition, a high density of CaBP28K positive neurons was also observed. These neurons were small, showing one, two or three short and non-branching dendritic trunks. The distribution and orientation of the immunoreactive cell bodies in the nucleus pretectalis superficialis parvicellularis suggests that the neurons might be interneurons and/or projecting neurons.

Animals↗

Subtractive cloning of a hybrid human endogenous retrovirus and calbindin gene in the prostate cell line PC3.

A complementary DNA clone containing human endogenous retrovirus-like sequences spliced to sequences encoding human calbindin was discovered by complementary DNA subtraction analysis between two human prostate cell lines, PC3 and DU145. This gene is presumably activated by the long terminal repeat of the retrovirus-like sequence. It belongs to a member of the retrovirus-like H (tRNA(his) primer binding sequence) family. The level of this transcript is high in PC3, derived from a prostate bone metastasis, but not in DU145, derived from a prostate brain metastasis.

Aged↗

Expression of calbindin-D28k in human fallopian tubes.

The present study was aimed at investigating the expression of calbindin-D28k (CaBP-D28k) in human fallopian tube, which were collected from 33 childbearing age women undergoing abdominal hysterectomy with adnexectomy for benign disease in the pelvic cavity. These women had normal menstrual cycle and history of normal pregnancy. Isthmus, ampullary and umbrella segments of fallopian tubes were respectively collected. These specimens were divided into 6 groups based on their menstrual cycles: early-proliferative stage (n=6), mid-proliferative stage (n=5), late-proliferative stage (n=5), early-secretory stage (n=7), mid-secretory stage (n=5) and late-secretory stage (n=5). The expressions of CaBP-D28k protein and mRNA in fallopian tubes were determined by immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) methods. Positive expressions of CaBP-D28k protein and mRNA were observed in human fallopian tubes. There was no significant difference in the expression of CaBP-D28k protein among the isthmus, ampulla and umbrella segments in the same phase of menstrual cycle (P>0.05). However, in the menstrual cycle, the expression level of CaBP-D28k protein in the epithelium was the lowest during the early- and mid-proliferative stages and increased in both the late-proliferative and early-secretory stages (P<0.05), and then decreased in the mid- and late-secretory stages (P<0.05). The expressed CaBP-D28k protein was disposed to gobbets or dispersed sheets in cytoplasm in the early- and mid- proliferative stages, and showed concentrated granules on the top of cells in the late-proliferative and early-, mid-secretory stages. Then in the late-secretory stage redistribution renewed as in the early- and mid-proliferative stages. The CaBP-D28k mRNA obviously increased in the late-proliferative and early-secretory stages (P<0.05). These findings indicate that the expressions of CaBP-D28k protein and mRNA exist in human fallopian tubes and exhibit a cyclic change.

Calbindin 1↗

[Structure, expression and control of calbindins-D].

The Calbindins-D (CaBP9K and 28K), like calmodulin, belong to a group of intracellular proteins that bind calcium with high affinity. Each protein is encoded by a separate gene and there is no direct filiation between the two genes. We have demonstrated the tissue-specific expression and regulation of CaBP9K gene. This gene is expressed in the intestine, placenta and uterus of the rat as a single 0.5kb long transcript. Exogenous 1,25(OH)2D3 triggers the rapid synthesis of CaBP9K mRNA and accumulation of translatable CaBP9K mRNA in the duodenum of vitamin D-deficient rats. Calcium also stimulates CaBP9K gene expression in this tissue. In contrast 1,25(OH)2D3 does not change the uterine concentration of CaBP9K but estrogen stimulates the transcription of the CaBP9K gene in the uterus. The promoter region of rat CaBP9K gene contains 1 TATA box and 4 CAAT box-type sequences and several steroid hormone regulatory elements. The CaBP9K gene is therefore a suitable model for studying the tissue-specific regulation of gene expression by steroid hormones.

Animals↗