Endothelial cell surfaces play key roles in several important physiologic and pathologic processes such as blood clotting, angiogenic responses, and inflammation. Partanen et al. (1992) cloned and characterized a novel type of human endothelial cell surface receptor tyrosine kinase designated TIE for 'tyrosine kinase with Ig and EGF homology domains.' Cells transfected with TIE cDNA expression vector produced glycosylated polypeptides of 117 kD that were reactive to antisera raised against the TIE carboxy terminus. Expression of the TIE gene appears to be restricted to certain cell lines; large amounts of TIE mRNA were detected in endothelial cell lines and in some myeloid leukemia cell lines having erythroid and megakaryoblastoid characteristics. The TIE receptor tyrosine kinase may be involved in multiple protein-protein interactions, possibly including cell adhesion to the vascular endothelium.
Loughna and Sato (2001) showed that the combinatorial function of angiopoietin-1 (601667) and the orphan receptor TIE1 is critical for the development of the right-hand side venous system but is dispensable for the left-hand side venous system.
Gene whose expression is detected by cDNA array hybridization: transporters, signal transduction. Also, relative transcript level reproducibly decreases during IVM Rozenn Dalbis-Tran and Pascal Mermilloda
Expression regulated by
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Ovarian localization
Theca
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Involvement of Angiopoietin-Tie System in Bovine Follicular Development and Atresia: Messenger RNA Expression in Theca Interna and Effect on Steroid Secretion Hayashi KG, et al .
Angiogenesis is involved in the local mechanisms that regulate follicular development and ovulation. Recently, the angiopoietin (ANPT)-Tie system has been shown to be required to regulate angiogenesis and blood vessel regression. Expression of the ANPT-Tie system in the cyclic ovary suggests that the relative changes in the expression of ANPT-1 and ANPT-2 influence the stability of ovarian blood vessels. This study aimed to investigate 1) the mRNA expression for ANPT-1, ANPT-2 and endothelial cell specific receptors Tie1 and Tie2 in theca interna (TI) of the bovine developing, mature and atretic follicles by using semi-quantitative RT-PCR, and 2) the effect of ANPT on the secretion of steroid hormones from bovine preovulatory follicles in vitro using a microdialysis system (MDS) implanted in the thecal layer. Bovine follicles were classified into developing, mature and atretic according to the size, the follicular fluid content of estradiol (E2) and progesterone (P4), and the characteristics of granulosa cells (GC). Both ANPT and Tie mRNA were expressed in TI, whereas GC expressed ANPT mRNA only. The expression of ANPT-2 mRNA was decreased in the mature follicles. This resulted in a decrease in the ANPT-2/ANPT-1 ratio (an index of instability of blood vessels), indicating that the blood vessels became more stable or mature. The early atretic follicles showed a higher ANPT-2/ANPT-1 ratio together with higher Tie2 mRNA expression than other follicles at healthy or later atretic stages stages. This may imply that blood vessels become unstable at the initial stage of follicular atresia. In both mid and late atretic follicles, Tie2 mRNA expression dramatically decreased, indicating a disruption of the ANPT-Tie system. In the MDS experiment, an infusion of ANPT-1 or ANPT-2 increased P4 release, whereas both ANPTs inhibited the release of androstenedione. Additionally, ANPT-1 increased E2 release. Collectively, the present study showed that the mRNA expression for ANPT-1, ANPT-2, Tie1 and Tie2 changes during follicular development, maturation and atresia in bovine follicles, and ANPTs affect steroidgenesis in the preovulatory follicle. The results suggest that ANPT-Tie system is involved the structural (angiogenesis) and secretory changes that occur during follicular development and atresia.