Laser ablation of the sonic hedgehog-a-expressing cells during fin regeneration affects ray branching morphogenesis

• Published in: Developmental biology 2012-05, Vol.365 (2), p.424-433
• Main Authors: Zhang, Jing, Jeradi, Shirine, Strähle, Uwe, Akimenko, Marie-Andrée
• Format: Article
• Language: English
• Subjects: Animal Fins - cytology; Animal Fins - embryology; Animal Fins - radiation effects; Animals; Animals, Genetically Modified; Body Patterning - physiology; Body Patterning - radiation effects; Cells, Cultured; Danio rerio; Fin regeneration; fins; genetically modified organisms; GFP; Hedgehog Proteins - antagonists & inhibitors; Hedgehog Proteins - physiology; Laser ablation; Lasers; morphogenesis; ontogeny; osteoblasts; Ray branching; Regeneration; shha; Transgenic line; Zebrafish; Zebrafish - embryology; Zebrafish - metabolism; Zebrafish Proteins - antagonists & inhibitors; Zebrafish Proteins - physiology
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/j.ydbio.2012.03.008

The zebrafish fin is an excellent system to study the mechanisms of dermal bone patterning. Fin rays are segmented structures that form successive bifurcations both during ontogenesis and regeneration. Previous studies showed that sonic hedgehog (shha) may regulate regenerative bone patterning based on its expression pattern and functional analysis. The present study investigates the role of the shha-expressing cells in the patterning of fin ray branches. The shha expression domain in the basal epidermis of each fin ray splits into two prior to ray bifurcation. In addition, the osteoblast proliferation profile follows the dynamic expression pattern of shha. A zebrafish transgenic line, 2.4shh:gfpABC#15, in which GFP expression recapitulates the endogenous expression of shha, was used to specifically ablate shha-expressing cells with a laser beam. Such ablations lead to a delay in the sequence of events leading to ray bifurcation without affecting the overall growth of the fin ray. These results suggest that shha-expressing cells direct localized osteoblast proliferation and thus regulate branching morphogenesis. This study reveals the fin ray as a new accessible system to investigate epithelial–mesenchymal interactions leading to organ branching. ► shha expression in the basal epidermis splits into two before fin ray bifurcation. ► Osteoblast proliferation profile follows the dynamic expression pattern of shha. ► Laser ablation of shha+cells perturbs osteoblast markers and impairs ray branching.