Expression of BMP signalling pathway members in the developing zebrafish inner ear and lateral line

In this paper we describe the mRNA expression patterns of members of the bo ne morphogenetic protein (BMP) signalling pathway in the developing zebrafi sh ear. bmp2b, 4, and 7 are expressed in discrete areas of otic epithelium, some of which correspond to sensory patches. bmp2b and 4 mark the developi ng cristae before and during the appearance of differentiated hair cells. b mp4 is also expressed in a dorsal, non-sensory region of the ear. Expressio n of bmps in cristae is conserved between zebrafish, chick, and mouse, but there are also notable differences in ear expression patterns between these species. Of five zebrafish BMP antagonists, only one (follistatin) shows s ignificant expression in the otic epithelium. The type I receptor bmpr-1B s hows localised expression in the ear epithelium. Mediators of BMP signallin g, smad1 and smad5, are expressed in statoacoustic and lateral line ganglia ; smad5 is also expressed at low levels throughout the ear epithelium. An i nhibitory smad, smad6, is expressed laterally in the car epithelium. Latera l line primordia and neuromasts also express bmp2b, 4, follistatin, smad1, and smad5. The conservation of bmp expression in cristae among different sp ecies adds weight to the growing evidence that BMPs are required for the de velopment of the vertebrate car. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.