Expression patterns of tbx genes during chick atrial development

Abstract

T-box gene family encodes a set of transcription factors that are involved in various developmental processes. We cloned T-box genes, tbx2, −5 and −20, from chick embryonic heart, and examined their expression patterns in the developing atrium from stage 14 to 27 by in situ hybridization. In the looped heart at stages 14 – 16, tbx2, −5 and −20 were expressed in the atrioventricular (AV) canal, in which valvuloseptal endocardial cushion tissue would later develop. These three genes were also expressed in the dorsal mesentery, through which pulmonary veins connect to the left atrium. During the atrial septation at later stages, tbx5 was expressed in the primitive auricles, sinus venosus and caval veins. In the developing atrial septum, tbx5 and −20 were expressed in the spina vestibuli, and tbx2 and −5 in the primary septum. tbx20 was expressed in the AV endocardial cushion tissue. Results suggest that differentially expressed tbx2, −5, −20 may play an important role in the atrial development, such as septation and pulmonary venous development.