J Biol Chem, Vol. 274, Issue 25, 17661-17670, June 18, 1999
Structure and Evolution of the Alternatively Spliced Fast
Troponin T Isoform Gene
Elizabeth A.
Bucher,
Gurtej K.
Dhoot,
Mark M.
Emerson,
Margaret
Ober, and
Charles P.
Emerson Jr.
From the Department of Cell and Developmental Biology, University
of Pennsylvania School of Medicine,
Philadelphia, Pennsylvania 19104-6058
The vertebrate fast skeletal muscle troponin T
gene, TnTf, produces a complexity of isoforms through
differential mRNA splicing. The mechanisms that regulate splicing
and the physiological significance of TnTf isoforms are poorly
understood. To investigate these questions, we have determined the
complete sequence structure of the quail TnTf gene, and we
have characterized the developmental expression of alternatively
spliced TnTf mRNAs in quail embryonic muscles. We report the
following: 1) the quail TnTf gene is significantly larger
than the rat TnTf gene and has 8 non-homologous exons, including a pectoral muscle-specific set of alternatively spliced exons; 2) specific sequences are implicated in regulated exon splicing;
3) a 900-base pair sequence element, composed primarily of intron
sequence flanking the pectoral muscle-specific exons, is tandemly
repeated 4 times and once partially, providing direct evidence that the
pectoral-specific TnT exon domain arose by intragenic duplications; 4)
a chicken repeat 1 retrotransposon element resides upstream of this
repeated intronic/pectoral exon sequence domain and is implicated in
transposition of this element into an ancestral genome; and 5) a large
set of novel isoforms, produced by regulated exon splicing, is
expressed in quail muscles, providing insights into the developmental
regulation, physiological function, and evolution of the vertebrate
TnTf isoforms.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.