Multiciliated cells (MCCs) drive directional fluid flow in diverse tubular organs and
are essential for development and homeostasis of the vertebrate central nervous system,
airway, and reproductive tracts. These cells are characterized by dozens or hundreds of
long, motile cilia that beat in a coordinated and polarized manner. In recent years,
genomic studies have not only elucidated the transcriptional hierarchy for MCC
specification, but also identified myriad new proteins that govern MCC ciliogenesis, cilia
beating, or cilia polarization. Interestingly, this burst of genomic data has also highlighted
the obvious importance of the “ignorome,” that large fraction of vertebrate genes that
remain only poorly characterized. Understanding the function of novel proteins with
little prior history of study presents a special challenge, especially when faced with large
numbers of such proteins. Here, we explored the MCC ignorome by defining the
subcellular localization of 260 poorly defined proteins in vertebrate MCCs in vivo. Based
on this localization data, we selected some targets of MCC ignorome for further
functional studies because they could possibly play key roles in the regulation of
ciliogenesis. We characterized Myo5c as the motor for basal body apical migration,
vi
Arhgef18 as the RhoA signaling activator at the basal bodies, and Dennd2b as a regulator
of actin network formation and ciliogenesis. All of these findings have deepened our
understanding about molecular mechanisms of related cellular process. This study
exemplifies the power of high content protein localization screening as the bridging step
between large-scale omics data and functional study of specific proteins.Cellular and Molecular Biolog
