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Brian Oppermann, Weiyan Zhang, Kristine Magabo, Marc Kantorow; Identification and Spatial Analysis of Metallothioneins Expressed by the Adult Human Lens. Invest. Ophthalmol. Vis. Sci. 2001;42(1):188-193.
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purpose. Metallothioneins (MTs) are a large family of proteins involved in
multiple protective pathways including binding of toxic metals, free
radical scavenging, and oxidative stress. Increased expression of the MT IIA gene in age-related cataractous relative
to normal human lenses, suggesting a role for MTs in the maintenance of
lens transparency, has previously been detected. The MT family consists
of many closely related isoforms grouped into four classes (I–IV). As
a first step toward defining the function of MTs in the lens, the range
and expression patterns of those MT isoforms expressed by the adult
human lens were established.
methods. Normal human lenses were microdissected into epithelia and fiber cells.
Primers specific for individual MT isoforms were designed. MT
transcripts were monitored in whole lenses, epithelia, and fibers by
RT-PCR and confirmed to be authentic by sequencing. MT protein levels
were evaluated by immunoblotting and by immunostaining.
results. Transcripts encoding MT classes I and II but not III or IV were
detected in adult human lenses. In addition to MT IIA, five other MT
transcripts were identified including IE, IF, IG, IH, and IL. MT IIA
was detected almost exclusively in the lens epithelium, whereas the
class I isoforms were detected at high levels in both lens epithelia
and fibers. MT protein was detected almost exclusively in the lens
conclusions. The present report establishes the spectrum of MTs expressed by the
adult human lens, defines their spatial expression patterns in lens
epithelia and fibers, and demonstrates that MT protein is abundantly
present in the lens epithelium.
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