Calreticulin, a Ca 2+ binding chaperone of the endoplasmic reticulum, is also highly
expressed in the embryonic heart, and knockout of the calreticulin gene is lethal during
embryogenesis because of impaired cardiac development. The protein is down-regulated
after birth, and elevated expression of calreticulin in newborn hearts is associated with
severe cardiac pathology and death. Here we show that the transcription factor Nkx2. 5
activates expression of the calreticulin gene in the heart. Binding of chicken ovalbumin …