A role for the <i>Drosophila</i> Bag-of-marbles protein in the differentiation of cystoblasts from germline stem cells

TLDR

Cell differentiation often involves cell‑cycle changes in daughter cells, and the Drosophila bam gene has been implicated in driving germline stem cell daughters (cystoblasts) to differentiate, possibly by modulating the cell cycle. The study aims to use newly generated Bam antibodies to probe Bam’s role in germ cell development. The authors generated specific antibodies against Bam and employed them to examine its function during germ cell differentiation. Bam localizes to both the fusome and cytoplasm, with potentially distinct functions, and bam mutants arrest germ cells in a stem‑like, mitotically active state, supporting a model in which Bam regulates cystocyte differentiation.

Abstract

ABSTRACT Cell differentiation commonly dictates a change in the cell cycle of mitotic daughters. Previous investigations have suggested that the Drosophila bag of marbles (bam) gene is required for the differentiation of germline stem cell daughters (cystoblasts) from the mother stem cells, perhaps by altering the cell cycle. In this paper, we report the preparation of antibodies to the Bam protein and the use of those reagents to investigate how Bam is required for germ cell development. We find that Bam exists as both a fusome component and as cytoplasmic protein and that cytoplasmic and fusome Bam might have separable activities. We also show that bam mutant germ cells are blocked in differentiation and are trapped as mitotically active cells like stem cells. A model for how Bam might regulate cystocyte differentiation is presented.