Structure and expression of the mouse cardiac calsequestrin gene

Calsequestrin is a sarcoplasmic reticulum protein, which plays a predominant role in diastolic Ca2+-storage in the mammalian heart. The present study was designed to define the gene structure, developmental and tissue specific expression of the murine, cardiac isoform of calsequestrin. Two sets of genomic libraries (lambda phage and PAC) were screened using the mouse cardiac calsequestrin cDNA, and several overlapping clones were isolated. These clones were characterized using restriction enzyme digestion, Southern blotting and partial sequencing. The cardiac calsequestrin gene consists of 11 exons and its 5' flanking region is characterized by the presence of a TATA-like box, muscle specific promoter elements such as 7 E-boxes, 1 MEF-2, 1 MCBF and 1 Repeat (musS) motifs, as well as several muscle non-specific transcriptional elements (AP-2A, NRE1, NRE2, p53, Spel and TFI-IIA). Expression of the cardiac isoform of calsequestrin was first detected on day 11 pre-birth and approached adult levels by day 4 post-birth. Expression of cardiac calsequestrin was also detected in adult fast-twitch skeletal muscle, thyroid, testis and epididymis tissues. This genomic characterization of cardiac calsequestrin may form the basis for further evaluation of its regulatory role in Ca2+ homeostasis and contractility in the murine heart.