Distinct patterns of notochord mineralization in zebrafish coincide with the localization of Osteocalcin isoform 1 during early vertebral centra formation

• Published in: BMC Developmental Biology
• Main Authors: Bensimon-Brito, Anabela, Cardeira, João, Cancela, Maria Leonor, Huysseune, Ann, Witten, Paul Eckhard
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2012
• Subjects: Biology and Life Sciences; Vertebral column; Notochord; ATLANTIC SALMON; DANIO-RERIO; GENE-EXPRESSION; ACTINOPTERYGIAN FISHES; ALKALINE-PHOSPHATASE; CAUDAL SKELETON; AXIAL SKELETON; TELEOST FISH; Vertebral fusion; Osteocalcin; SALMON SALMO-SALAR; MATRIX GLA PROTEIN; Atlantic salmon; Salmo salar
• Online Access: https://biblio.ugent.be/publication/4432230; http://hdl.handle.net/1854/LU-4432230; https://doi.org/10.1186/1471-213X-12-28; https://biblio.ugent.be/publication/4432230/file/5756147

Background: In chondrichthyans, basal osteichthyans and tetrapods, vertebral bodies have cartilaginous anlagen that subsequently mineralize (chondrichthyans) or ossify (osteichthyans). Chondrocytes that form the vertebral centra derive from somites. In teleost fish, vertebral centrum formation starts in the absence of cartilage, through direct mineralization of the notochord sheath. In a second step, the notochord is surrounded by somite-derived intramembranous bone. In several small teleost species, including zebrafish (Danio rerio), even haemal and neural arches form directly as intramembranous bone and only modified caudalmost arches remain cartilaginous. This study compares initial patterns of mineralization in different regions of the vertebral column in zebrafish. We ask if the absence or presence of cartilaginous arches influences the pattern of notochord sheath mineralization. Results: To reveal which cells are involved in mineralization of the notochord sheath we identify proliferating cells, we trace mineralization on the histological level and we analyze cell ultrastructure by TEM. Moreover, we localize proteins and genes that are typically expressed by skeletogenic cells such as Collagen type II, Alkaline phosphatase (ALP) and Osteocalcin (Oc). Mineralization of abdominal and caudal vertebrae starts with a complete ring within the notochord sheath and prior to the formation of the bony arches. In contrast, notochord mineralization of caudal fin centra starts with a broad ventral mineral deposition, associated with the bases of the modified cartilaginous arches. Similar, arch-related, patterns of mineralization occur in teleosts that maintain cartilaginous arches throughout the spine. Throughout the entire vertebral column, we were able to co-localize ALP-positive signal with chordacentrum mineralization sites, as well as Collagen II and Oc protein accumulation in the mineralizing notochord sheath. In the caudal fin region, ALP and Oc signals were clearly produced both by the notochord epithelium and ...