Spatio-Temporal Expression of Chondroitin Sulfate Antigens in Early Chick Pituitary and Thyroid

Le résumé fourni par la source

The chondroitin sulfate antigens d1C4 and TC2 have been hypothesized to play a role in cartilage differentiation in the limb and early morphogenesis of the heart in chick embryos. The antibody d1C4 recognizes a native epitope on glycosaminoglycan (GAG) chains enriched in chondroitin-6-sulfate found on the hyalectin proteoglycans such as versican and aggrecan. Previous studies also show that TC2 antibody recognizes a native epitope on GAG chains enriched in chondroitin-4-sulfate that occurs in the myocardial basement membrane. However, the expression and function of d1C4 and TC2 was unknown in early development of the thyroid and pituitary glands. We hypothesized that we would observe expression of d1C4 and TC2 antigens and, based on this hypothesis, utilized immunohistochemistry to localize these chondroitin sulfate antigens in the pituitary and thyroid. We also localized the additional chondroitin sulfate antigen recognized by CS-56 as well as the hyalectin, versican, to determine if it may be expressed in these locations. CS-56 has been known to recognize GAG chains enriched in chondroitin-6-sulfate and chondroitin-4-sulfate found on hyalectins. It was determined that during stages HH17, HH24, and HH28, d1C4, CS56, and versican localized predominantly in basement membranes and extracellular matrix (ECM) of Rathke’s pouch and the thyroid. TC2 asymmetrically stained basement membrane of Rathke’s pouch at HH17 and then in the ECM of tissues surrounding Rathke’s pouch and thyroid. During HH35 and HH38, d1C4, CS56, and versican staining decreased in the pituitary and thyroid, with low level localization in specific regions of gland rudiments. TC2 was not present in these later stages. D1C4 and CS56 staining patterns coincided with that of versican, suggesting that d1C4 and CS56 epitopes are found on glycosaminoglycan (GAG) chains of this or other hyalectin proteoglycans. This suggests further that versican or other hyalectin proteoglycans may be primarily important in early stages of pituitary and thyroid development. It also suggests that expression of these chondroitin sulfate antigens may correlate with or perhaps are regulated by other important signaling molecules crucial for pituitary and thyroid development, such as BMP4 and BMP2, and transcription factors, such as Titf/Nik-1.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.