FGF-dependent mechanosensory organ patterning in zebrafish

During development, organ primordia reorganize to form repeated functional units. In zebrafish ( Danio rerio), mechanosensory organs called neuromasts are deposited at regular intervals by the migrating posterior lateral line ( pLL) primordium. The pLL primordium is organized into polarized rosettes representing proto- neuromasts, each with a central atoh1a- positive focus of mechanosensory precursors. We show that rosettes form cyclically from a progenitor pool at the leading zone of the primordium as neuromasts are deposited from the trailing region. fgf3/10 signals localized to the leading zone are required for rosette formation, atoh1a expression, and primordium migration. We propose that the fibroblast growth factor ( FGF) source controls primordium organization, which, in turn, regulates the periodicity of neuromast deposition. This previously unrecognized mechanism may be applicable to understanding segmentation and morphogenesis in other organ systems.