Gene expression patterns underlying proximal–distal skeletal segmentation in late‐stage zebrafish,Danio rerio

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Abstract
Timing and pattern of expression of ten candidate segmentation genes or gene pairs were reviewed or examined in developing median fins of late‐stage zebrafish,Danio rerio. We found a general correspondence in timing and pattern of expression between zebrafish fin radial segmentation and tetrapod joint development, suggesting that molecular mechanisms underlying radial segmentation have been conserved over 400 million years of evolution. Gene co‐expression during segmentation (5.5–6.5 mm SL) is similar between tetrapods and zebrafish:bmp2b,bmp4,chordin, andgdf5in interradial mesenchyme and ZS;bapx1,col2a1,noggin3, andsox9ain chondrocytes. Surprisingly,wnt9ais not expressed in the developing median fins, thoughwnt9bis detected. In contrast to all other candidate segmentation genes we examined,bapx1is not expressed in the caudal fin, which does not segment. Together, these data suggest a scenario of gene interactions underlying radial segmentation based on the patterns and timing of candidate gene expression. Developmental Dynamics 236:3111–3128, 2007