Differential expression of Isk mRNAs in mouse tissue during development and pregnancy.

The molecular isoform of the cDNA clone Isk present in the AT-1 atrial tumor cell line was characterized by molecular cloning of Isk cDNA. Since Isk mRNA was found in mouse heart, kidney, and uterus, a complete study of its expression during development in the heart and kidney was performed, in addition to its expression in the uterus during pregnancy. In the heart, Isk showed a 4-fold upregulation during the perinatal period followed by a 20-fold decrease between birth and the adult state. Furthermore, the two 0.9- and 3.4-kb transcripts were differentially regulated after birth. In the kidney, Isk progressively increased 10-fold, reaching steady-state adult values at 21 days. Isk mRNA levels in the uterus increased threefold at late pregnancy and decreased sixfold rapidly after birth. The Isk gene is differentially expressed during development in kidney and cardiac tissue, and both Isk transcripts appeared to be differentially regulated. Furthermore, the drastic changes in transcript levels before delivery and after birth suggest that Isk plays a significant role in myometrium during late pregnancy and delivery.