International Mammalian Genome Society

F49 Molecular Cloning and Sequencing of the HRC Gene from Mouse Heart Reveals a Highly Unstable GAG Repeat

Shundi Shi, Steven R. Brunnert. Columbia University, Institute of Comparative Medicine 630 W. 168th Street, Mail Box 17, New York, NY 10032

Histidine-rich calcium binding protein (HRC) is a luminal sarcoplasmic reticulum protein that has been mapped to human Chromosome 19 and mouse Chromosome 7 and considered a candidate gene of several genetic diseases in humans and mice. We derived a  2407-bp clone encoding for a 738 AA protein by PCR from C57BL/6J mouse heart and found a highly unstable GAG repeat  in the middle of the coding region. The instability of the GAG repeat could be detected within individual C57BL/6J and DBA/2J mice in both genomic DNA and cDNA, and no polymorphism was found between two mouse HRC cDNAs except the unstable GAG repeats. At normal physiologic conditions,  no GAG expansion was found in the unstable GAG repeat region in the dystrophic cardiac calcinosis (DCC) sensitive DBA/2J mice. However, after DCC induced by freeze thaw injury, PCR results reveal that these DCC positive individual animals tend to have a higher number of GAG repeats  in HRC, while DCC negative individual animals tend to have a smaller number of GAG repeats. The phenomenon of gene shifting with different physiologic conditions in mammalian genomic DNA has not been previously reported.