Evidence for stanniocalcin gene expression in mammalian bone

Stanniocalcin 2 (STC2): a universal tumour biomarker and a potential therapeutical target

Stanniocalcin 2 (STC2) is a glycoprotein which is expressed in a broad spectrum of tumour cells and tumour tissues derived from human breast, colorectum, stomach, esophagus, prostate, kidney, liver, bone, ovary, lung and so forth. The expression of STC2 is regulated at both transcriptional and post-transcriptional levels; particularly, STC2 is significantly stimulated under various stress conditions like ER stress, hypoxia and nutrient deprivation. Biologically, STC2 facilitates cells dealing with stress conditions and prevents apoptosis. Importantly, STC2 also promotes the development of acquired resistance to chemo- and radio- therapies. In addition, multiple groups have reported that STC2 overexpression promotes cell proliferation, migration and immune response. Therefore, the overexpression of STC2 is positively correlated with tumour growth, invasion, metastasis and patients' prognosis, highlighting its potential as a biomarker and a therapeutic target. This review focuses on discussing the regulation, biological functions and clinical importance of STC2 in human cancers. Future perspectives in this field will also be discussed.

＜Editors' Choice＞ Stanniocalcin-1 mRNA expression in soft-tissue tumors

Stanniocalcin-1 (STC1) is a glycoprotein that was originally identified as a calcium-regulating hormone in bony fish, and that has been shown to also critically mediate cell growth, proliferation and differentiation, etc. in humans. Increased STC1 expression levels have been previously detected in different human cancer samples, such as those isolated from lung, breast, ovary, colon, pancreas, and liver tumors; thus, the present study evaluated STC1 expression in various soft-tissue tumors. STC1 mRNA isolated from 16 cell lines and 186 clinical soft-tissue tumor specimens were analyzed via quantitative real-time PCR, and the calculated expression levels were normalized to those exhibited by STC1-expressing MDA-MB-231 cells. The results of these analyses did not reveal any specific histological tumor types that displayed significantly increased STC1 expression; however, they did not indicate that STC1 expression was significantly higher in malignant compared to benign soft-tissue tumors. Furthermore, in adipocytic tumors, STC1 expression in dedifferentiated liposarcomas was found to be highest and lowest in lipoma tissues, respectively, suggesting that adipocytic tumors may express increasely high levels of STC1 mRNA as they become histologically more advanced. STC1 expression correlates with the malignancy grade in soft-tissue tumors.

Stanniocalcin-1 protein expression profile and mechanisms in proliferation and cell death pathways in prostate cancer

Prostate cancer (PCa) is one of the most prevalent male tumours. Stanniocalcin-1 (STC1) is a glycoprotein and, although the role of STC1 in human cancer is poorly understood, it is suggested to be involved in the development and progression of different neoplasms. This study investigated the protein expression profile of STC1 in PCa and benign prostatic hyperplasia (BPH) samples and STC1 signalling during cell proliferation and cell death in vitro using cell lines. We found higher levels of STC1 in PCa when compared to BPH tissue and that STC1 inhibited forskolin stimulation of cAMP in PC-3 cells. A monoclonal antibody against STC1 was effective in reducing cell proliferation, in promoting cell cycle arrest, and in increasing apoptosis in the same cells. Since STC1 acts as a regulator of prostatic tissue signalling, we suggest that this protein is a novel candidate biomarker for prostate tumour clinical progression and a potential therapeutic target.

ZBTB16 induces osteogenic differentiation marker genes in dental follicle cells independent from RUNX2

BACKGROUND

Dental follicle cells (DFCs) are neural crest cell-derived cells and the genuine precursor cells of cementoblast and alveolar osteoblasts. After osteogenic differentiation, expression levels of the transcription factor zinc factor and BTB domain containing 16 (ZBTB16) were significantly increased. ZBTB16 is associated with the process of osteogenic differentiation in bone marrow-derived mesenchymal stem cells and crucial for the expression of the osteogenic transcription factor runt-related transcription factor 2 (RUNX2). It is proposed that ZBTB16 plays also a crucial role for the differentiation of DFCs into osteoblasts.

METHODS

In this study, the differentiation of DFCs by alkaline phosphatase (ALP) activity measurement, alizarin red staining, and electron-dispersive x-ray spectrometry (EDX) analysis is investigated. The expression of ZBTB16 during osteogenic differentiation and the expression of osteogenic differentiation markers were assessed by real-time reverse transcription polymerase chain reaction. Glucocorticoid stimulation was inhibited using RU486 (11β-[p-(Dimethylamino)phenyl]-17β-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one), and ZBTB16 was overexpressed via transient transfection of an expression vector.

RESULTS

After the initiation of osteogenic differentiation, ZBTB16 levels were increased highly in DFCs, whereas RUNX2 was expressed constitutively only. An EDX analysis verified the differentiation of DFCs into osteoblast-like cells because clusters of mineralization consisted of hydroxyapatite. ZBTB16 induced the expression of nuclear receptor subfamily 4, group A, member 3; osteocalcin; and stanniocalcin 1 (STC1) but not of RUNX2 and ALP in DFCs. STC1 was upregulated in DFCs downstream of ZBTB16 and after the osteogenic differentiation. The overexpression of STC1 in DFCs increased the expression of ZBTB16 and specific markers for biomineralization.

CONCLUSIONS

The present study shows that ZBTB16 induced the expression of osteogenic differentiation markers independently of RUNX2. Moreover, STC1 is a new candidate for the evaluation of late mechanisms of osteogenic differentiation downstream of ZBTB16.

Stanniocalcin 2 is associated with ectopic calcification in α-klotho mutant mice and inhibits hyperphosphatemia-induced calcification in aortic vascular smooth muscle cells

Ectopic calcification of soft tissues can have severe clinical consequences especially when localized to vital organs such as heart, arteries and kidneys. Mammalian stanniocalcin (STC) 1 and 2 are glycoprotein hormones identified as calcium/phosphate-regulating hormones. The mRNA of STCs is upregulated in the kidney of α-klotho mutant (kl/kl) mice, which have hypercalcemia, hyperphosphatemia and hypervitaminosis D and exhibit a short life span, osteopenia and ectopic calcification. In the present study, we investigated the distribution and localization of STCs in kl/kl mice. Quantitative RT-PCR revealed that renal mRNA expression of STC2 was increased in both kl/kl mice and fibroblast growth factor 23 (Fgf23)-null mice compared with wild type mice. Interestingly, STC2 protein was focally localized with the calcified lesions of renal arterioles, renal tubular cells, heart and aorta in kl/kl mice. In vitro analysis of rat aortic vascular smooth muscle (A-10) cells showed that inorganic phosphate (Pi) stimulation significantly increased STC2 mRNA levels as well as that of osteocalcin, osteopontin and the type III sodium-dependent phosphate co-transporter (PiT-1), and induced STC2 secretion. Interestingly, the knockdown with a small interfering RNA or the over-expression of STC2 showed acceleration and inhibition of Pi-induced calcification in A-10 cells, respectively. These results suggest that the up-regulation of STC2 gene expression resulting from abnormal α-klotho-Fgf23 signaling may contribute to limitation of ectopic calcification and thus STC2 represents a novel target gene for cardio-renal syndrome.

Evolution and roles of stanniocalcin

In fish, stanniocalcin-1 (STC1) is a key endocrine factor that acts on gill, intestine and kidney to regulate serum calcium and phosphate homeostasis. The recent identification and study of mammalian STCs (STC1 and STC2) revealed that the hormones are made in virtually all tissues and they act primarily as paracrine/autocrine factors to regulate various biological functions. Based on their ubiquitous expression patterns and generally undetectable levels in blood serum, it is unlikely that the mammalian STCs play important roles in serum Ca(2+)/P(i) homeostasis. However current evidences still support the local action of STCs in Ca(2+) and P(i) transport, probably via their action on Ca(2+)-channels and Na(+)/P(i) co-transporter. At present, information about the sequence, expression and distribution of the STC receptor(s) is lacking. However, recent emerging evidence hints the involvement of STC1 and STC2 in the sub-cellular functions of mitochondria and endoplasmic reticulum respectively, particularly responding to oxidative stress and unfolded protein response. With increasing evidence that demonstrates the local actions of STCs, the focus of the research has been moved to cellular inflammation and carcinogenesis. This review integrates the information available on STCs in fish and mammals, focusing mainly on their embryonic origin, tissue distribution, their potential regulatory mechanisms and the modes of action, and their physiological and pathophysiological functions, particularly in cancer biology.

Human stanniocalcin-1 or -2 expressed in mice reduces bone size and severely inhibits cranial intramembranous bone growth

Stanniocalcin-1 (STC1) and -2 (STC2) are highly related, secreted, homodimeric glycoproteins that are significantly upregulated by different forms of stress including high phosphate levels. Transgenic mice that constitutively express either human STC1 or STC2 exhibit intra-uterine growth restriction and permanent post-natal growth retardation. STC1 is expressed in chondrocytic and osteoblastic cells during murine development and can enhance differentiation of calvarial cells in culture. Therefore, there is mounting evidence that stanniocalcins (STCs) modulate bone development in vivo. To further define the effects of stanniocalcins on skeletal development, we performed a series of measurements on components of the axial, appendicular, and cranial skeleton in transgenic and wildtype mice. We show that skeletal growth is retarded and that the intramembranous bones of the cranium exhibit a particularly severe delay in suture closure. The posterior frontal suture remains patent throughout the lifetime of human STC1 and STC2 transgenic mice. We did not observe significant effects on chondrogenesis: however, calvarial cells exhibited reduced viability, proliferation and delayed differentiation, indicating that developing osteoblasts are particularly sensitive to the levels of STCs. Given the evidence linking STC1 to cellular phosphate homeostasis, we assessed the expression of a variety of phosphate regulators in transgenic and wildtype calvarial cells and found significantly lower levels of Mepe, Dmp1, Sfrp4 in transgenic cells without a change in Pit1 or Pit2. Collectively these data support a direct regulatory role for STCs in osteoblasts and suggest that overexposure to these factors inhibits normal skeletal development without significant changes in patterning.

The murine stanniocalcin 2 gene is a negative regulator of postnatal growth

Stanniocalcin (STC), a secreted glycoprotein, was first studied in fish as a classical hormone with a role in regulating serum calcium levels. There are two closely related proteins in mammals, STC1 and STC2, with functions that are currently unclear. Both proteins are expressed in numerous mammalian tissues rather than being secreted from a specific endocrine gland. No phenotype has been detected yet in Stc1-null mice, and to investigate whether Stc2 could have compensated for the loss of Stc1, we have now generated Stc2(-/-) and Stc1(-/-) Stc2(-/-) mice. Although Stc1 is expressed in the ovary and lactating mouse mammary glands, like the Stc1(-/-) mice, the Stc1(-/-) Stc2(-/-) mice had no detected decrease in fertility, fecundity, or weight gain up until weaning. Serum calcium and phosphate levels were normal in Stc1(-/-) Stc2(-/-) mice, indicating it is unlikely that the mammalian stanniocalcins have a major physiological role in mineral homeostasis. Mice with Stc2 deleted were 10-15% larger and grew at a faster rate than wild-type mice from 4 wk onward, and the Stc1(-/-) Stc2(-/-) mice had a similar growth phenotype. This effect was not mediated through the GH/IGF-I axis. The results are consistent with STC2 being a negative regulator of postnatal growth.

Molecular interactions between breast cancer cells and the bone microenvironment drive skeletal metastases

Breast cancer cells preferentially spread to bone. Bone metastases are currently incurable and therefore better treatments need to be developed. Metastasis is an inefficient, multi-step process. Specific aspects of both breast cancer cells and the bone microenvironment contribute to the development of bone metastases. Breast cancers express chemokine receptors, integrins, cadherins, and bone-resorbing and bone-forming factors that contribute to the successful and preferential spread of tumor to bone. Bone is rich in growth factors and cell types that make it a hospitable environment for breast cancer growth. Once breast cancer cells enter the bone, a highly complex vicious cycle develops, in which breast cancer cells secrete factors that act on bone cells and other cells within the bone (stem cells, T cells, platelets, adipocytes, fibroblasts, and endothelial cells), causing them to secrete factors that act on adjacent cancer cells. The steps in the metastatic cascade and the vicious cycle within bone offer unique targets for adjuvant treatments to treat and cure bone metastases.

Avian stanniocalcin-2 is expressed in developing striated muscle and joints

The glycoprotein hormone stanniocalcin (STC) has originally been described in the teleost kidney. Since then, STC homologs have been identified in various genomes including human, mouse, rat, Xenopus and zebrafish. In mammals, two STC genes, STC1 and STC2, are known. We cloned a chicken STC homolog to analyze its expression pattern during chick development. Sequence analyses revealed a high sequence similarity of the chicken STC (cSTC) clone to mammalian STC2. Interestingly the expression pattern of cSTC2 largely resembles those of murine STC1: we found expression of cSTC2 in the nephric tubules, in the myocardium, in skeletal muscle cells from the onset of differentiation, and in synovial joint anlagen of the limbs.

The murine stanniocalcin 1 gene is not essential for growth and development

The stanniocalcin 1 (STC1) gene is expressed in a wide variety of tissues, including the kidney, prostate, thyroid, bone, and ovary. STC1 protein is considered to have roles in many physiological processes, including bone development, reproduction, wound healing, angiogenesis, and modulation of inflammatory response. In fish, STC1 is a hormone that is secreted by the corpuscles of Stannius and is involved in calcium and phosphate homeostasis. To determine the role of STC1 in mammals, we generated Stc1-null mice by gene targeting. The number of Stc1-/- mice obtained was in accordance with Mendelian ratios, and both males and females produced offspring normally. No anatomical or histological abnormalities were detected in any tissues. Our results demonstrated that Stc1 function is not essential for growth or reproduction in the mouse.

Stanniocalcin 1 acts as a paracrine regulator of growth plate chondrogenesis

During embryogenesis, the expression of mammalian stanniocalcin (STC1) in the appendicular skeleton suggests its involvement in the regulation of longitudinal bone growth. Such a role is further supported by the presence of dwarfism in mice overexpressing STC1. Yet, the STC 1 inhibitory effect on growth may be related to both postnatal metabolic abnormalities and prenatal defective bone formation. In our study, we used an organ culture system to evaluate the effects of STC on growth plate chondrogenesis, which is the primary determinant of longitudinal bone growth. Fetal rat metatarsal bones were cultured in the presence of recombinant human STC (rhSTC). After 3 days, rhSTC suppressed metatarsal growth, growth plate chondrocyte proliferation and hypertrophy/differentiation, and extracellular matrix synthesis. In addition, rhSTC increased the number of apoptotic chondrocytes in the growth plate. In cultured chondrocytes, rhSTC increased phosphate uptake, reduced chondrocyte proliferation and matrix synthesis, and induced apoptosis. All these effects were reversed by culturing chondrocytes with rhSTC and phosphonoformic acid, an inhibitor of phosphate transport. The rhSTC-mediated inhibition of metatarsal growth and growth plate chondrocyte proliferation and hypertrophy/differentiation was abolished by culturing metatarsals with rhSTC and phosphonoformic acid. Taken together, our findings indicate that STC1 inhibits longitudinal bone growth directly at the growth plate. Such growth inhibition, likely mediated by an increased chondrocyte phosphate uptake, results from suppressed chondrocyte proliferation, hypertrophy/differentiation, and matrix synthesis and by increased apoptosis. Last, the expression of both STC1 and its binding site in the growth plate would support an autocrine/paracrine role for this growth factor in the regulation of growth plate chondrogenesis.

Upregulated expression of stanniocalcin-1 during adipogenesis

Stanniocalcin-1 (STC-1) is a 56-kDa homodimeric protein originally discovered in bony fish, where it protects against toxic levels of environmental calcium by lowering the uptake of calcium via the gills and by increasing the reabsorption of phosphate in the kidney. Here we report expression of STC-1 in mammalian white and brown fat tissue. Coexpression of STC-1 and perilipin confirmed the presence of STC-1 in mature fat cells. Neoplastic adipocytes in well-differentiated liposarcomas also stained for STC-1, while the frequency of STC-1-positive cells was lower in high-grade liposarcomas. The kinetics of STC-1 expression during adipogenesis was investigated in 3T3-LI cells, which can be induced to adipocyte differentiation. Untreated 3T3-L1 cells displayed negligible amounts of STC-1, whereas 3T3-L1 cells, treated with an adipogenic cocktail, upregulated the expression of STC-1 concomitantly with acquisition of the adipocytic phenotype. We have previously reported a high expression of STC-1 in postmitotically differentiated neurons and megakaryocytes. We have also shown that expression of STC-1 confers increased resistance to hypoxic and oxidative stress in neurons. Given this, our findings suggest that STC-1, also in terminally differentiated adipocytes, may function as a "survival factor", which contributes to the maintenance of the integrity of mature adipose tissue.

Stanniocalcin 1 alters muscle and bone structure and function in transgenic mice

Fish stanniocalcin (STC) inhibits uptake of calcium and stimulates phosphate reabsorption. To determine the role of the highly homologous mammalian protein, STC-1, we created and characterized transgenic mice that express STC-1 under control of a muscle-specific promoter. STC-1 transgenic mice were smaller than wild-type littermates and had normal growth plate cartilage morphology but increased cartilage matrix synthesis. In STC-1 mice, the rate of bone formation, but not bone mineralization, was decreased. Increased cortical bone thickness and changes in trabeculae number, density, and thickness in STC-1 mice indicated a concomitant suppression of osteoclast activity, which was supported by microcomputed tomography analyses and histochemistry. Skeletal muscles were disproportionately small and showed altered function and response to injury in STC-1 mice. Electron microscopy indicated that muscle mitochondria were dramatically enlarged in STC-1 mice. These changes in STC-1 mice could not be explained by deficits in blood vessel formation, as vascularity in organs and skeletal tissues was increased as was induction of vascularity in response to femoral artery ligation. Our results indicate that STC-1 can affect calcium homeostasis, bone and muscle mass and structure, and angiogenesis through effects on osteoblasts, osteoclasts, myoblasts/myocytes, and endothelial cells.

Characterization of gene expression induced by RET with MEN2A or MEN2B mutation

Germ-line point mutations of the RET gene are responsible for multiple endocrine neoplasia (MEN) type 2A and 2B that develop medullary thyroid carcinoma and pheochromocytoma. We performed a differential display analysis of gene expression using NIH 3T3 cells expressing the RET-MEN2A or RET-MEN2B mutant proteins. As a consequence, we identified 10 genes induced by both mutant proteins and eight genes repressed by them. The inducible genes include cyclin D1, cathepsins B and L, and cofilin genes that are known to be involved in cell growth, tumor progression, and invasion. In contrast, the repressed genes include type I collagen, lysyl oxidase, annexin I, and tissue inhibitor of matrix metalloproteinase 3 (TIMP3) genes that have been implicated in tumor suppression. In addition, six RET-MEN2A- and five RET-MEN2B-inducible genes were identified. Among 21 genes induced by RET-MEN2A and/or RET-MEN2B, six genes including cyclin D1, cathepsin B, cofilin, ring finger protein 11 (RNF11), integrin-alpha6, and stanniocalcin 1 (STC1) genes were also induced in TGW human neuroblastoma cells in response to glial cell line-derived neurotrophic factor stimulation. Because the STC1 gene was found to be highly induced by both RET-MEN2B and glial cell line-derived neurotrophic factor stimulation, and the expression of its product was detected in medullary thyroid carcinoma with the MEN2B mutation by immunohistochemistry, this may suggest a possible role for STC1 in the development of MEN 2B phenotype.

Stanniocalcin 1 (STC1) protein and mRNA are developmentally regulated during embryonic mouse osteogenesis: the potential of stc1 as an autocrine/paracrine factor for osteoblast development and bone formation

STC1, a mammalian homologue of stanniocalcin (STC) which plays a major role in calcium/phosphate homeostasis in fish, has been recently isolated. We have characterized the spatiotemporal distribution of STC1 mRNA and protein during mouse embryonic development generally and osteogenesis specifically. Northern blotting analysis of whole embryos showed that STC1 mRNA is highly and differentially expressed during embryogenesis. By in situ hybridization, STC1 mRNA was detected early in mesenchymal condensations and was then found to be highly expressed in perichondrial cells, periosteal cells, and then osteoblasts during endochondral bone formation. In bones forming by intramembranous ossification, STC1 mRNA was not detected until osteogenic cells appeared. The cellular distribution of STC1 protein closely corresponded to that of its mRNA, but the protein was also detected in hypertrophic chondrocytes. In the MC3T3-E1 osteogenic cell model, STC1 protein and mRNA were detectable throughout proliferation and differentiation stages but levels were relatively higher late during nodule formation/mineralization phases. For comparison, STC1 mRNA was also found in epithelial cells of both embryonic and adult intestine that had not previously been described among tissues responsive to calcium/phosphate transport. These results suggest that STC1 is expressed in a time- and cell-specific manner and may play an autocrine/paracrine role during osteoblast development and bone formation.

Prospect of a stanniocalcin endocrine/paracrine system in mammals

Stanniocalcin (STC) is a calcium- and phosphate-regulating hormone produced in bony fish by the corpuscles of Stannius, which are located close to the kidney. It is a major antihypercalcemic hormone in fish. As the corpuscles of Stannius are absent, and antihypercalcemic hormones are basically not necessary, in mammals, the discovery of a mammalian homolog, STC1, was surprising and intriguing. STC1 displays a relatively high amino acid sequence identity (approximately 50%) with fish STC. In contrast to fish STC, STC1 is expressed in many tissues, including kidney. More recently, a human gene encoding the second stanniocalcin-like protein, STC2, was identified. STC2 has a lower identity (approximately 35%) with STC1 and fish STC. Similar to STC1, STC2 is also expressed in a variety of tissues. Research into the functions of STCs in mammals is still at an early stage, and the ultimate physiological and pathological roles of STCs have not yet been established. A few studies indicate that STC1, similar to fish STC, stimulates phosphate absorption in the kidney and intestine, but the function of STC2 is still unknown. However, several interesting findings have been reported on their cellular localization, gene structure, and expression in different physiological and pathological conditions, which will be clues in elucidating the functions of STCs in mammals. STC1 expression is enhanced by hypertonicity in a kidney cell line or by ischemic injuries and neural differentiation in the brain. STC1 expression in the ovary is also enhanced during pregnancy and lactation. Calcitriol upregulates STC1 and downregulates STC2 expression in the kidney. Interestingly, STC1 and STC2 are expressed in many tumor cell lines, and the expression of STC2 is enhanced by estradiol in breast cancer cells. STC2 is also expressed in pancreatic islets. These results suggest that the biological repertoires of STCs in mammals will be considerably larger than in fish and may not be limited to mineral metabolism. This brief review describes recent progress in mammalian STC research.

Overexpression of human stanniocalcin affects growth and reproduction in transgenic mice

In mammals stanniocalcin (STC) is widely expressed, and in the kidney and gut it regulates serum calcium levels by promoting phosphate reabsorption. To shed further light on its functional significance in mammals we have created several lines of mice that express a human STC (hSTC) transgene. Three lines expressed the hSTC transgene, but only two lines exhibited high expression and contained circulating hSTC, and in these animals there was a reduction in postnatal growth (30-50%) that persisted after weaning. Moreover, even wild-type pups exhibited a growth retardation phenotype when nursed by a transgenic foster mother, and this implies that hSTC overexpression deleteriously affects maternal behavior and/or lactation. The reproductive potential of female transgenic mice was also compromised, as evidenced by significantly smaller litter sizes, but transgenic male fertility was unchanged even though the transgene was most highly expressed in testes. Interestingly, transgene-derived serum hSTC increased significantly after puberty and was severalfold higher in females than in males, suggesting a gender-specific mechanism for maintaining elevated circulating levels of STC. Blood analysis revealed that both transgenic lines had elevated phosphate and decreased alkaline phosphatase levels, indicative of altered kidney and bone metabolism. These studies provide the first evidence that STC is involved in growth and reproduction and reaffirm its role in mineral homeostasis.

Microarray analysis of the in vivo effects of hypophysectomy and growth hormone treatment on gene expression in the rat

Complementary DNA microarrays containing 3000 different rat genes were used to study the consequences of severe hormonal deficiency (hypophysectomy) on the gene expression patterns in heart, liver, and kidney. Hybridization signals were seen from a majority of the arrayed complementary DNAs; nonetheless, tissue-specific expression patterns could be delineated. Hypophysectomy affected the expression of genes involved in a variety of cellular functions. Between 16-29% of the detected transcripts from each tissue changed expression level as a reaction to this condition. Chronic treatment of hypophysectomized animals with human GH also caused significant changes in gene expression patterns. The study confirms previous knowledge concerning certain gene expression changes in the above-mentioned situations and provides new information regarding hypophysectomy and chronic human GH effects in the rat. Furthermore, we have identified several new genes that respond to GH treatment. Our results represent a first step toward a more global understanding of gene expression changes in states of hormonal deficiency.

Singular contributions of fish neuroendocrinology to mammalian regulatory peptide research

During the past 20 years, several bioactive peptides have been identified in teleost fishes that subsequently have been shown to play important regulatory roles in mammalian physiology. The urophysis, corpuscles of Stannius and Brockmann body are anatomical structures particular to fish that have no obvious counterpart in mammals. Extracts and/or cDNA libraries prepared from these tissues have been used to identify for the first time urotensin II (U-II), urotensin-I (U-I), stanniocalcin and glucagon-like peptide-1 (GLP-1). Although U-II and U-I were originally regarded as exclusively the products of the teleost urophysis, the peptides have a wide phylogenetic distribution across the vertebrate lineage, including mammals. U-II is localized to motor neurones in the human spinal cord and is a potent vasoconstrictor that may be implicated in the pathogenesis of heart failure. The human ortholog of urotensin-I is urocortin which is synthesized in selected regions of the brain and is the endogenous ligand for the CRF type 2 receptor. Urocortin is believed to important in mediating the effects of stress on appetite. Stanniocalcin is involved in maintaining calcium and phosphate homeostasis in teleost fish. An ortholog of stanniocalcin has a widespread distribution in mammalian tissues and is postulated to regulate renal phosphate excretion and to protect neurons against damage during cerebral ischemia. The biological actions and therapeutic potential of GLP-1 in humans are now fully appreciated but the peptide was first identified as a domain in a preproglucagon cDNA prepared from anglerfish Brockmann bodies. In contrast to mammalian preproglucagons, GLP-1 is present in anglerfish preproglucagon as the bioactive, truncated sequence [corresponding to human GLP-1(7-37)] rather than the inactive, N-terminally extended form [corresponding to GLP-1(1-37)]. Failure to appreciate the significance of this fact retarded progress in the field for several years.

Regulation by 1alpha,25-dihydroxyvitamin D(3) of expression of stanniocalcin messages in the rat kidney and ovary

Regulation by vitamin D(3) of expression of the genes for stanniocalcins 1 and 2 (STC-1 and STC-2) was studied and their levels were shown to be oppositely regulated in the kidney and to remain unaffected in the ovary. Female rats were treated with calcitriol, the active form of vitamin D(3), and alterations in the levels of STC-1 and STC-2 mRNA were determined by Northern blot analysis in the kidney and ovary where the STC-1-expressing cells have previously been identified by in situ hybridization histochemistry. In the kidney, calcitriol treatment increased the STC-1 mRNA levels more than 3-fold, but decreased the STC-2 message to trace levels. In the ovary, however, both STC-1 and STC-2 mRNA levels were not significantly affected by the calcitriol treatment. These results support the hypotheses that (1) STC-1 and STC-2 have opposite effects on calcium and phosphate homeostasis, namely anti-hypercalcemic and anti-hypocalcemic actions, respectively, and (2) the mammalian stanniocalcin system acquired, in addition to the role in the systemic mineral metabolism, a role in the reproduction system that operates independently of the systemic condition.