Abstract :
[en] Bone morphogenetic proteins (BMPs) control many developmental and
physiological processes, including skeleton formation and homeostasis. Previous studies in
zebrafish revealed the crucial importance of proper BMP signaling before 48 h post-fertilization
(hpf) for cartilage formation in the skull. Here, we focus on the involvement of the BMP
pathway between 48 and 96 hpf in bone formation after 96 hpf. Using BMP inhibitors and
the expression of a dominant-negative BMP receptor, we analyze whether the loss of BMP
signaling affects osteoblastogenesis, osteoblast function and bone mineralization. To this
end, we used the transgenic zebrafish line Tg(osterix:mCherry), detection of nitric oxide
(NO) production, and alizarin red staining, respectively. We observed that inhibition of
BMP signaling between 48 and 72 hpf led to a reduction of NO production and bone
mineralization. Osteoblast maturation and chondrogenesis, on the other hand, seemed
unchanged. Osteoblast function and bone formation were less affected when BMP
signaling was inhibited between 72 and 96 hpf. These results suggest that for the onset of
bone formation, proper BMP signaling between 48 and 72 hpf is crucial to ensure
osteoblast function and ossification. Furthermore, detection of NO in developing zebrafish
larvae appears as an early indicator of bone calcification activity.
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