Multicilin promotes centriole assembly and ciliogenesis during multiciliate cell differentiation

Abstract

Multiciliate cells function prominently in the respiratory system, brain ependyma, and female reproductive tract to produce vigorous fluid flow along epithelial surfaces. These specialized cells form during development when epithelial progenitors undergo an unusual form of ciliogenesis, in which they assemble and project hundreds of motile cilia. Notch inhibits multiciliate cell formation in diverse epithelia, but how progenitors overcome lateral inhibition and initiate multiciliate cell differentiation is unknown. Here we identify a coiled-coil protein, termed multicilin, which is Notch regulated and highly expressed in developing epithelia where multiciliate cells form. Inhibiting multicilin function specifically blocks multiciliate cell formation in the Xenopus skin and kidney, while ectopic expression induces the differentiation of multiciliate cells in ectopic locations. Multicilin localizes to the nucleus, where it directly activates the expression of genes required for multiciliate cell formation, including FoxJ1 and genes mediating centriole assembly. Multicilin is also necessary and sufficient to promote multiciliate cell differentiation in mouse airway epithelial cultures. These findings suggest that multicilin initiates multiciliate cell differentiation in diverse tissues, by coordinately promoting the transcriptional changes required for motile ciliogenesis and centriole assembly.

mab21-l3 regulates cell fate specification of multiciliate cells and ionocytes

“…This positive feedback may ensure robust progression of ionocyte differentiation. Also, miR-449 microRNAs, whose genomic locus is close to the multicilin gene 15 , could be functionally linked with mab21-l3, because they have been shown to regulate MCC differentiation through inhibition of the Notch signalling pathway in both Xenopus embryonic epidermis and mammalian airway epithelial cells 35 .…”

“…The expression was first detected in the presumptive ectoderm in the animal region at the early gastrula stage (stage 10.5), and became restricted to the ventral ectoderm with a spotted pattern at the late gastrula stage (stage 12/13). At neurula and tailbud stages (stage [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], mab21-l3 is expressed in the epidermis with a salt-and-pepper pattern.…”

“…3b,d), which has been shown to act upstream of foxj1 (ref. 15). Because multicilin has been reported to promote cell cycle exit 15 , we examined cell proliferation in mab21-l3 knockdown embryos.…”

“…15). Because multicilin has been reported to promote cell cycle exit 15 , we examined cell proliferation in mab21-l3 knockdown embryos. Mab21-l3 MO significantly enhanced the accumulation of an M-phase marker, phospho-histone H3 (Fig.…”

“…Cell fate specifications of MCCs and ionocytes are known to be suppressed by the Notch pathway in various developing epithelia [5][6][7][8][9][10][11][12][13][14] . However, MCCspecific and ionocyte-specific transcriptional programmes are governed by different master regulators: a coiled-coil protein multicilin 15 and a forkhead transcription factor foxj1 (refs [16][17][18] for MCCs and another forkhead transcription factor foxi1 (refs 7-9,19-21) for ionocytes. This raises the possibility that an unidentified common regulator(s) links the Notch pathway to both MCC and ionocyte specifications.…”