Caprin Controls Follicle Stem Cell Fate in the Drosophila Ovary

Adult stem cells must balance self-renewal and differentiation for tissue homeostasis. The Drosophila ovary has provided a wealth of information about the extrinsic niche signals and intrinsic molecular processes required to ensure appropriate germline stem cell renewal and differentiation. The factors controlling behavior of the more recently identified follicle stem cells of the ovary are less well-understood but equally important for fertility. Here we report that translational regulators play a critical role in controlling these cells. Specifically, the translational regulator Caprin (Capr) is required in the follicle stem cell lineage to ensure maintenance of this stem cell population and proper encapsulation of developing germ cells by follicle stem cell progeny. In addition, reduction of one copy of the gene fmr1, encoding the translational regulator Fragile X Mental Retardation Protein, exacerbates the Capr encapsulation phenotype, suggesting Capr and fmr1 are regulating a common process. Caprin was previously characterized in vertebrates as Cytoplasmic Activation/Proliferation-Associated Protein. Significantly, we find that loss of Caprin alters the dynamics of the cell cycle, and we present evidence that misregulation of CycB contributes to the disruption in behavior of follicle stem cell progeny. Our findings support the idea that translational regulators may provide a conserved mechanism for oversight of developmentally critical cell cycles such as those in stem cell populations

Characterization of DRP2, a novel human dystrophin homologue

The currently recognised dystrophin protein family comprises the archetype, dystrophin, its close relative, utrophin or dystrophin-related protein (DRP), and a distantly related protein known as the 87K tyrosine kinase substrate. During the course of a phylogenetic study of sequences encoding the characteristic C-terminal domains of dystrophin-related proteins, we identified an unexpected novel class of vertebrate dystrophin-related sequences. We term this class dystrophin-related protein 2 (DRP2), and suggest that utrophin/DRP be renamed DRP1 to simplify future nomenclature. DRP2 is a relatively small protein, encoded in man by a 45 kb gene localized to Xq22. It is expressed principally in the brain and spinal cord, and is similar in overall structure to the Dp116 dystrophin isoform. The discovery of a novel relative of dystrophin substantially broadens the scope for study of this interesting group of proteins and their associated glycoprotein complexes