XB-ART-44680Nat Cell Biol January 29, 2012; 14 (2): 140-7.
Multicilin promotes centriole assembly and ciliogenesis during multiciliate cell differentiation.
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 regulated by Notch and highly expressed in developing epithelia where multiciliate cells form. Inhibiting multicilin function specifically blocks multiciliate cell formation in Xenopus skin and kidney, whereas 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 indicate that multicilin initiates multiciliate cell differentiation in diverse tissues, by coordinately promoting the transcriptional changes required for motile ciliogenesis and centriole assembly.
PubMed ID: 22231168
PMC ID: PMC3329891
Article link: Nat Cell Biol
Genes referenced: foxj1 cdh1 foxj1.2 gal.2 hyls1 mcc mcidas myc notch1 odc1 pcnt tjp1 tspan31
Morpholinos: foxj1 MO1
Article Images: [+] show captions
|Figure 5. MCI activates MCC gene expression(a–h) Shown is the expression of α-tubulin (a–d) or for FoxJ1 (e–h) in embryos injected with a control morpholino (a,e), with MCI-MOspl (b, f) or with MCI-HGR RNA along with nlacz RNA as a tracer (d,h) or alone as a control (c,g). RNA injected embryos were treated with DEX at stage 11.5, and all embryos were fixed at stage 26, and stained with X-gal (light blue). Scale bar=0.5mm. Insert shows a higher power (i) Animal caps were isolated at stage 10 from embryos injected with ICD RNA, MCI-HGR RNA (MCI), or the two RNAs together, treated with DEX at st11, and extracted for total RNA at stage 12, approximately two hours later. Shown is the log level of expression (±s.d.) relative to ICD values set at zero, as measured in triplicate using QT-PCR and after normalization against a ubiquitously expressed RNA, ODC. (j–m) Single animal blastomeres were injected with MCI-HGR RNA at the two-cell stage. At stage 11, half of the injected and uninjected control embryos were treated with cyclohexemide (CHX) for one hour, and then additionally treated with DEX for another hour to induce MCI-HGR activity. CHX is sufficient to block the onset of α-tubulin expression in the controls (compare k to j), indicating that the CHX treatment is effective, but does not block the activation of α-tubulin by MCI-HGR (m). Scale bar (j)=0.2mm.|
|Figure 6. Domains required for MCI function(a) Diagram of MCI. (b–e) Shown are embryos injected with RNA encoding different MCI mutants as indicated, fixed at stage 13/14, and stained for α-tubulin RNA expression (f–i) Confocal images of the skin of embryos injected with RNA encoding different MCI mutants, fixed at stage 28, and stained with ZO-1 (red) and acetylated tubulin (green) antibodies to label cell boundaries and cilia, respectively. Scale bars=0.5mm (b–e), 10 microns (f–h), or 20 microns (i).|