Ontogeny of the H19 gene in sheep and effect of maternal fasting on its expression in the fetus.

Mapped on the same chromosome as the Insulin-like Growth Factor II (IGF-II), an important factor regulating fetal growth, the H19 gene, is believed to play a role during embryogenesis and to share similar regulatory elements with IGF-II possibly by an enhancer competition system. This study was designed to characterize the ontogeny of H19 in sheep and the effect of maternal fasting on the expression of fetal IGF-II and H19 mRNA. A partial cDNA clone for the ovine H19 gene was isolated and used as a probe for RNase protection analysis. The ontogeny of H19 in liver, skeletal muscle and heart of ovine fetuses at 62,100 and 130 days, lambs at 1 month and adult sheep revealed high tissue levels of H19 mRNA during fetal life that decreased significantly after birth. Maternal fasting significantly decreased fetal liver H19 mRNA expression but did not alter fetal IGF-II mRNA expression. These results suggest that H19, like IGF-II, may play an important role in the regulation of fetal growth and define an environmental condition whereby these two genes are regulated independently.