Patterns of expression of retinoic acid receptor beta 2 (RAR-beta2)-LacZ reporter gene in the embryonic foregut.

Vitamin A and its active form retinoic acid (RA) are essential for normal embryonic development. Maternal vitamin A deficiency in experimental animals is known to produce various developmental anomalies including foregut malformations and lung hypoplasia. However, there is a little known about the role of RA receptors in the developing foregut. Our aim was to study the pattern of expression of retinoic acid receptor beta 2 (RAR-beta2) in the region of the foregut during the early stages of embryonic development. Normal mouse embryos homozygous for the lacZ-fused RAR-beta2 promoter transgene were studied to detect the expression of RAR-beta2 in the embryonic foregut. Transverse and sagittal sections of the embryos were taken at the region of the foregut to observe for The normal pattern of expression of RARbeta2-LacZ between 9.5-12.5 days post conception. RAR-beta2-LacZ was expressed in the foregut tube on 9.5 and 10.5 dpc, mainly in the oesophageal part and maximally in the region of tracheo-oesophageal fold formation. This expression faded on day 11.5, and was not seen on 12.5 dpc. The change of RAR-beta2 expression between 9.5-11.5 dpc coincided with the time of tracheo-esophageal separation of the foregut. Our study has shown a possible RA-driven genetic activity during embryonic foregut development.