Expression of TIS21 in the Embryonic Liver of BALB/c Mouse

Abstract

TIS (TPA inducible sequence) genes are known as the primary response genes in the SW3T3 fibroblast treated with TPA. TIS21 and TISI genes are constitutively expressed in the BALB/c mouse thymus, lung, spleen and stomach. In order to understand the function of TIS21, we investigated the changes in its expression in the BALB/c mouse, from embryo to 6 months. Northern blot hybridization results showed an increase in TIS21 expression in the whole embryo in the second week of gestation. Further investigation showed that the expression was particularly strong in the embryonic liver. After birth, on the contrary, TIS21 expression disappeared in the liver. In order to confirm the northern results, we used in situ histochemical hybridization to determine the tissues which express TIS21 mRNA during murine embryonic development. Embryonic liver and brain from a 15.5-day-old rat embryo showed strong expression of TIS21 gene : the gene was expressed in the whole embryonic liver and in the neuroepithelium near the lateral ventricle of the brain at this stage. Liver is known to be the primary locus of hematopoiesis during murine embryonic development. Transient expression of TIS21 in the embryonic liver strongly suggests an important role for TIS21 during the embryonic hematopoiesis.