Duplication and distinct expression patterns of two thrombospondin-1 isoforms in teleost fishes.
Two types of thrombospondin-1 (named TSP-1a and TSP-1b) were cloned from two species of teleosts, the Nile tilapia and medaka. Phylogenetic analysis of these TSP-1 sequences, together with those available from other vertebrates further demonstrated that two types of TSP-1 exist only in teleosts, extending the finding in fugu and tetraodon to two additional fish species. The expression of both genes was examined using tilapia at various developmental stages. Tilapia TSP-1a and TSP-1b were each expressed in a wide range of tissues examined. The early expression of TSP-1b in both XX and XY gonads from 5dah (day after hatching) onwards suggested an important role in the formation of gonads, while the expression of TSP-1a only in ovaries during later stages of development (from 120dah onwards) may suggest that TSP-1a is involved in oogenesis. During the 14-day spawning cycle, the expression of both types of TSP-1 exhibited distinct peaks at day 5 (peak of vitellogenesis) and day 12 (oocyte maturation). In situ hybridization analyses revealed differential expression, with TSP-1a occurring in granulosa cells and TSP-1b in theca cells. Furthermore, both TSP-1a and -1b were expressed in skeletal tissues but with clear temporal and spatial differences. In contrast, only TSP-1b was found in the myosepta. The positive signals of both TSP-1a and TSP-1b were also detected in the heart and spleen, and TSP-1a in brain and intestine by both RT-PCR and in situ hybridization.
Wu
Feng-Rui
FR
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Science, Southwest University, Chongqing 400715, China.
Zhou
Lin-Yan
LY
Nagahama
Yoshitaka
Y
Wang
De-Shou
DS