Jan-Michael Kugler1, Ya-Wen Chen1, Ruifen Weng1,2 and Stephen M. Cohen1,2
1 - Institute of Molecular and Cell Biology, Singapore 138673, Singapore
2 - Department of Biological Sciences, National University of Singapore, Singapore 119613, Singapore
Published in PLoS ONE on 3 July 2013.
microRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by destabilizing target transcripts and/or inhibiting their translation. miRNAs are thought to have roles in buffering gene expression to confer robustness. miRNAs have been shown to play important roles during tissue development to control cell proliferation, differentiation and morphogenesis. Many miRNAs are expressed in the germ line of Drosophila, and functions have been reported for a few miRNAs in maintenance of stem cell proliferation during oogenesis. Here, we analyse the function of Drosophila miR-989 in oogenesis. miR-989 is abundant in ovaries. Mutants lacking miR-989 did not display gross abnormalities affecting egg chamber formation or maturation. However, the migration of the border cell cluster was severely delayed in miR-989 mutant egg chambers. We demonstrate that miR-989 function is required in the somatic cells in the egg chamber, not in germ line cells for border cell migration. Loss of miR-989 from a fraction of the border cell cluster was sufficient to impair cluster migration as a whole, suggesting a role in border cells. Gene ontology analysis reveals that many predicted miR-989 target mRNAs are implicated in regulating cell migration, cell projection morphogenesis, cell adhesion as well as receptor tyrosine kinase and ecdysone signalling, consistent with an important regulatory role for miR-989 in border cell migration.
Figure Legend: Border cell migration is delayed in miR-989 mutant egg chambers
a: Late stage 9 egg chambers, labelled with α-Slbo (white) and Phalloidin (green). Border cell clusters are highlighted by arrows. In miR-989 mutant egg chambers, border cells were frequently delayed relative to the migrating main body follicular epithelium.
b: Quantification of the border cell migration phenotype in stage 9 and stage 10A egg chambers. Border cell migration is delayed in miR-989 mutant egg chambers compared to heterozygous control egg chambers (*** p<0.001). X-Axis labels are in μm, error bars denote standard deviation.
c: Stage 10B egg chambers, labelled with α-Slbo (white) and Phalloidin (green). Border cell clusters are highlighted by arrows. Frequently, border cells had not reached the oocyte by this stage in miR-989 mutant egg chambers.
d: Quantification of the border cell migration phenotype in stage 10B egg chambers.
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