Fragile X mental retardation protein modulates the fate of germline stem cells in Drosophila.

Fragile X syndrome, a common form of inherited mental retardation, is caused by the loss of fragile X mental retardation protein (FMRP). FMRP, which may regulate translation in neurons, associates not only with specific mRNAs and microRNAs (miRNA), but also with components of the miRNA pathway, including Dicer and Argonaute proteins. In Drosophila, dFmr1 is also known to be involved in germ cell and oocyte specification; however, the question of whether dFmr1 is required for controlling the fate of germline stem cells (GSCs) has gone unanswered. Here we show that dFmr1 is required for both GSC maintenance and repressing differentiation. Furthermore, we demonstrate that in Drosophila ovary, dFmr1 protein interacts with Argonaute protein 1 (AGO1), a key component of the miRNA pathway. Thus dFmr1 could modulate the fate of GSCs, likely via the miRNA pathway. Our results provide the first evidence that FMRP might be involved in the regulation of adult stem cells.