Differential Expression of Wnt‐pathway in Late Fetal Ovine Heart and Lung Development

Abstract

Wnt signalling pathways critical to early cardiogenesis have not been extensively studied in sheep. The activity of Wnt signalling during the rapid heart growth occurring between late‐fetal and early newborn development is not known but may be important given that a right ventricular (RV) functional dominance occurs in utero, but a left ventricular (LV) dominance after birth. Thus our aims were to measure cardiopulmonary changes in 7 key proteins (Wnt3a, Wnt5a, Dvl‐1, phospho‐GSK3β, cdc42, ROCK2 and TCF7L2) and genes (Wnt4 and Wnt7b) in the Wnt signalling pathway in fetal and neonatal sheep. Lung, ventricular and atrial samples from pre‐term (age=128‐129 days; term=147 days), near‐term fetal (age=139‐141 days), and neonatal lambs (age= 5‐7 days post birth) were processed for western immunoblots and qRT‐PCR assays. Four main developmental patterns were evident. In the first pattern, the relative ventricular and atrial expression of Wnt3a, Dvl‐1, phospho‐GSK3β increased during fetal development (P<0.05), but decreased after birth (P<0.05). In the second pattern, fetal and newborn Wnt5a and ROCK2 expression was relatively constant, but with RV expression 2‐3 fold higher (P<0.025 – P<0.001). cdc42 expression decreased in both the ventricular and atrial samples. TCF7L2 expression decreased progressively in both ventricles from preterm to neonatal stages, but increased in the atria. Gene expression of Wnt4 and Wnt7b were greater in atrial samples than ventricular samples. Wnt3a, cdc42 and ROCK2 expression decreased in the lungs post birth but increased for Wnt5a and Dvl‐1. These data show that distinct patterns in Wnt signalling occur during ovine fetal growth, with evidence of differential expression between ventricles and atria.