Chromosomal localization and characterization of the stannin
*, X. Deng,
Melvin L. Billingsley
Department of Pharmacology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, Pennsylvania 17033, USA
Department of Biology, University of Delaware, Newark, Delaware 19716, USA
Received: 14 November 1997 / Accepted: 21 February 1998
Abstract. Stannin is a protein that has been localized to trimethyl-
tin-sensitive cell populations, and evidence suggests it plays a role
in the toxic effects of organotins. In this study, we have isolated a
mouse stannin genomic clone and have characterized the gene’s
intron-exon organization, promoter region, and chromosomal lo-
cation. We have also isolated a partial human stannin cDNA clone
and analyzed the open reading frame. The mouse genomic clone
spans ∼19 kb and consists of one intron and two exons. The splice
site consensus sequence was maintained at all intron-exon junc-
tions. Promoter analysis suggests that two putative promoter sites
exist, each containing multiple regulatory elements and transcrip-
tion factor-binding sites. Fluorescence in situ hybridization analy-
sis localized stannin to mouse Chromosome (Chr) 16 at band A2.
This region is homologous to the proximal region of human Chr 16
(16p13) to which stannin has been previously mapped. Sequence
analysis revealed that the 264-bp open reading frame was identical
between rat and mouse. The human sequence was 98% identical,
with two amino acid substitutions near the c-terminal end of the
peptide. These data suggest that stannin is highly conserved be-
tween species, and its unusual pattern of cellular expression may,
in part, be explained via cell-specific promoters.
Trimethyltin (TMT), a trialkyltin compound, is a potent neurotoxic
agent that selectively damages specific brain regions. Sensitive
neurons are found within the hippocampus, pyriform cortex, en-
torhinal cortex, amygdala, neocortex, and olfactory tubercle;
TMT-induced loss of these neurons results in severe behavioral
changes (Balaban et al. 1988). Intoxicated rodents experience dis-
orientation, seizures, and aggressiveness; humans who have been
accidentally exposed to TMT experience comparable behavioral
effects (Boyer 1989; Dyer et al. 1982). TMT also causes damage
to the renal and immune systems, affecting proximal tubular epi-
thelial cells and lymphocytes, respectively (Ghosh et al. 1989;
Opacka and Sparrow 1985).
The mechanism by which TMT renders its effects if not clear;
however, a number of varying hypotheses exist, including induc-
tion of apoptosis and excitotoxicity (Thompson et al. 1996; Patel
et al. 1990; Harkins and Armstrong 1992). We originally hypoth-
esized that a gene product may account for the selective nature of
TMT toxicity, sensitizing particular cells to the effects of TMT.
Toward this end, we isolated a cDNA encoding the protein, stan-
nin, from TMT-sensitive cells, using avidin-biotin subtractive hy-
bridization (Krady et al. 1990; Toggas et al. 1992). Stannin is an
88-amino acid protein that migrates in SDS-PAGE gels as a pep-
tide of approximately 14 kDa and has been localized to TMT-
sensitive tissues (Toggas et al. 1992). Southern blot analysis of
genomic DNA revealed that homologs of the stannin gene exist in
species as diverse as drosophila and human (Toggas et al. 1992).
Northern blot analysis has indicated that the stannin mRNA tran-
script is found in lymph, renal, and neural tissues, with greatest
expression in the spleen, followed by the hippocampus, neocortex,
cerebellum, striatum, midbrain, and kidney (Dejneka et al. 1997).
Western blot analysis has confirmed these findings (Dejneka et al.
There is evidence which suggests that stannin plays a role in
TMT toxicity. Immunohistochemical analysis of rat brain sections
showed that a loss of stannin expression occurred in hippocampal
pyramidal and dentate gyrus neurons after treatment with 8 mg/kg
TMT; however, no change in stannin expression in hippocampus
was evident following mechanical lesions of the fimbria-fornix
and perforant pathways, illustrating that changes in stannin expres-
sion correlate with TMT-induced cell loss (Patanow et al. 1997). In
vitro cell culture experiments revealed that stannin antisense oli-
godeoxynucleotides significantly protected primary neocortical
and hippocampal neurons from the neurotoxic and apoptotic ef-
fects of TMT, indicating that stannin is necessary, but not suffi-
cient, for TMT toxicity (Thompson et al. 1996).
Although these findings support a link between stannin and
TMT toxicity, they do not provide any insight into the normal
cellular function of stannin or clarify the mechanism by which it
sensitizes cells to organotins. It is possible that TMT interacts
directly with stannin and initiates a cascade of events that ulti-
mately lead to cellular damage and death.
Conversely, TMT may interact at the level of the stannin gene
and alter its rate of transcription. It has been reported that certain
genes, such as the metallothioneins and heme oxygenase, are in-
duced by heavy metals (Maines et al. 1976; Stuart et al. 1985).
Heme oxygenase (HO) catalyzes the rate-limiting step in heme
catabolism; two isozymes of this gene exist. The inducible iso-
zyme, HO-1, is activated by a number of metals, including stannic
and stannous chloride, cobalt and cadmium (Maines and Kappas
1976; Mitani et al. 1993; Neil et al. 1995). Promoter analysis and
in vitro binding experiments have identified unique regulatory el-
ements and transcription factor binding sites that participate in
cadmium-mediated induction of HO-1 (Alam 1994; Maeshima et
al. 1996; Takeda et al. 1994).
In view of these findings, and in order to better understand the
Correspondence to: M.L. Billingsley
* Present address: Departments of Biochemistry and Medicine, Emory
University College of Medicine, Atlanta, GA 30322, USA.
Mammalian Genome 9, 556–564 (1998).
© Springer-Verlag New York Inc. 1998