Novel expression of the stanniocalcin gene in fish

Abstract

It is currently accepted that the fish stanniocalcin (STC) gene is expressed exclusively in the corpuscles of Stannius (CS), unique endocrine glands on the kidneys of bony fishes. In this study, we have re-examined the pattern of fish STC gene expression in the light of the recent evidence for widespread expression of the gene in mammals. Surprisingly, we found by Northern blotting that the fish gene was also expressed in the kidneys and gonads, in addition to the CS glands. Moreover, Southern blotting of RT-PCR products revealed STC mRNA transcripts in all tissues assayed, including brain, heart, gill, muscle and intestine. In situ hybridization studies using digoxigenin-labeled riboprobes localized STC mRNA to chondrocytes, and both mature and developing nephritic tubules. Immunocytochemical staining indicated that the STC protein was widespread in cells of the gill, kidney, brain, eye, pseudobranch and skin. We also characterized the salmon STC gene, establishing that it was comprised of five exons as opposed to four in mammals. A single transcription start site was identified by primer extension 99 bp upstream of the start codon. This is the first evidence of STC gene expression in fish tissues other than the CS glands and suggests that, as in mammals, fish STC operates via both local and endocrine pathways.

The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and Excretion of Nitrogenous Waste

“…The gene for coho and chum salmon STC has been sequenced (779,842), and initial studies on the distribution of the STC mRNA and product suggested that they are expressed only in cells in the CS in fishes (439,713). However, more recent in situ hybridization and Northern blot studies have delineated STC expression in a variety of tissues in the rainbow trout and arawana (Osteoglossum bicirrhosum), including the kidney and gills (4,478), suggesting that STC may act as a paracrine as well as circulating hormone. Interestingly, two distinct STCs are expressed in the CS of the Atlantic salmon (782).…”

Mammalian stanniocalcins and cancer.

“…The fish STC gene, about 4 kb long, has been isolated from sockeye salmon (McCudden et al 2001a), and contains five exons. From comparative alignment of the gene structures (Fig.…”

“…The existence of mammalian STC1 mRNA in a wide variety of tissues was regarded as strikingly different to fish STC, as the www.endocrinology.org 361 latter was thought to be expressed exclusively in the unique endocrine gland, the CS. These observations led to a re-examination of fish STC gene expression (McCudden et al 2001a). Northern blotting of poly(A+) RNA detected STC mRNA in testis, ovary and anterior kidney at levels about 100-fold lower than in the CS, which may explain why they had been overlooked previously.…”

Activation of gill Ca2+-sensing receptor as a protective pathway to reduce Ca2+-induced cytotoxicity

“…In response to an increase in blood Ca 2C level, the CaSR-mediated STC1 release from CS glands inhibits gill Ca 2C uptake to restore homeostasis (Greenwood et al 2009, Lin et al 2014. Intriguingly, a re-examination of stc1 gene expression in fish tissues revealed the presence of stc1 transcript in gills of trout (McCudden et al 2001). Moreover, the expression of stc1 in gills of Japanese flounder was found to be stimulated by water salinity and Ca 2C (Shin & Sohn 2008 …”