Wang, L., Fu, C., Fan, H., Du, T., Dong, M., Chen, Y., Jin, Y., Zhou, Y., Deng, M., Gu, A., Jing, Q., Liu, T., and Zhou, Y. (2013) miR-34b regulates multiciliogenesis during organ formation in zebrafish. Development (Cambridge, England). 140(13):2755-2764.
Multiciliated cells (MCCs) possess multiple motile cilia and are distributed throughout the vertebrate body, performing important
physiological functions by regulating fluid movement in the intercellular space. Neither their function during organ development
nor the molecular mechanisms underlying multiciliogenesis are well understood. Although dysregulation of members of the miR-34
family plays a key role in the progression of various cancers, the physiological function of miR-34b, especially in regulating
organ formation, is largely unknown. Here, we demonstrate that miR-34b expression is enriched in kidney MCCs and the olfactory
placode in zebrafish. Inhibiting miR-34b function using morpholino antisense oligonucleotides disrupted kidney proximal tubule
convolution and the proper distribution of distal transporting cells and MCCs. Microarray analysis of gene expression, cilia
immunostaining and a fluid flow assay revealed that miR-34b is functionally required for the multiciliogenesis of MCCs in
the kidney and olfactory placode. We hypothesize that miR-34b regulates kidney morphogenesis by controlling the movement and
distribution of kidney MCCs and fluid flow. We found that cmyb was genetically downstream of miR-34b and acted as a key regulator of multiciliogenesis. Elevated expression of cmyb blocked membrane docking of centrioles, whereas loss of cmyb impaired centriole multiplication, both of which resulted in defects in the formation of ciliary bundles. Thus, miR-34b serves
as a guardian to maintain the proper level of cmyb expression. In summary, our studies have uncovered an essential role for miR-34b-Cmyb signaling during multiciliogenesis
and kidney morphogenesis.