Muscle wasted: a novel component of the Drosophila histone locus body required for muscle integrity.

Skeletal muscles arise by cellular differentiation and regulated gene expression. Terminal differentiation programmes such as muscle growth, extension and attachment to the epidermis, lead to maturation of the muscles. These events require changes in chromatin organization as genes are differentially regulated.

The intracellular domain of Dumbfounded affects myoblast fusion efficiency and interacts with Rolling pebbles and Loner.

Drosophila body wall muscles are multinucleated syncytia formed by successive fusions between a founder myoblast and several fusion competent myoblasts. Initial fusion gives rise to a bi/trinucleate precursor followed by more fusion cycles forming a mature muscle. This process requires the functions of various molecules including the transmembrane myoblast attractants Dumbfounded (Duf) and its paralogue Roughest (Rst), a scaffold protein Rolling pebbles (Rols) and a guanine nucleotide exchange factor Loner.

Actin on multiple fronts to generate a muscle fiber.

How the actin cytoskeleton is harnessed to fulfill its diverse cellular functions is a recurrent and intriguing question. In this issue of Developmental Cell, Kim et al. and Massarwa et al.

A positive feedback loop between Dumbfounded and Rolling pebbles leads to myotube enlargement in Drosophila.

In Drosophila, myoblasts are subdivided into founders and fusion-competent myoblasts (fcm) with myotubes forming through fusion of one founder and several fcm. Duf and rolling pebbles 7 (Rols7; also known as antisocial) are expressed in founders, whereas sticks and stones (SNS) is present in fcm. Duf attracts fcm toward founders and also causes translocation of Rols7 from the cytoplasm to the fusion site.