Margaret T Fuller

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Although changes in mitochondrial size and arrangement accompany both cellular differentiation and human disease, the mechanisms that mediate mitochondrial fusion, fission and morphogenesis in mammalian cells are not understood. We have identified two human genes encoding potential mediators of mitochondrial fusion. The mitofusins (Mfn1 and Mfn2) are(More)
Stem cell self-renewal can be specified by local signals from the surrounding microenvironment, or niche. However, the relation between the niche and the mechanisms that ensure the correct balance between stem cell self-renewal and differentiation is poorly understood. Here, we show that dividing Drosophila male germline stem cells use intracellular(More)
The Drosophila melanogaster fuzzy onions (fzo) gene encodes the first known protein mediator of mitochondrial fusion. During Drosophila spermatogenesis, mitochondria in early postmeiotic spermatids aggregate, fuse, and elongate beside the growing flagellar axoneme. fzo mutant males are defective in this developmentally regulated mitochondrial fusion and are(More)
Membrane fusion is required to establish the morphology and cellular distribution of the mitochondrial compartment. In Drosophila, mutations in the fuzzy onions (fzo) GTPase block a developmentally regulated mitochondrial fusion event during spermatogenesis. Here we report that the yeast orthologue of fuzzy onions, Fzo1p, plays a direct and conserved role(More)
Stem cells generate many differentiated, short-lived cell types, such as blood, skin, and sperm, throughout adult life. Stem cells maintain a long-term capacity to divide, producing daughter cells that either self-renew or initiate differentiation. Although the surrounding microenvironment or "niche" influences stem cell fate decisions, few signals that(More)
Mitochondrial fusion may regulate mitochondrial morphogenesis and underlie complementation between mitochondrial genomes in mammalian cells. The nuclear encoded mitochondrial proteins Mfn1 and Mfn2 are human homologues of the only known protein mediators of mitochondrial fusion, the Drosophila Fzo GTPase and Saccharomyces cerevisiae yFzo1p. Although the(More)
Stable intercellular bridges called ring canals form following incomplete cytokinesis, and interconnect mitotically or meiotically related germ cells. We show that ring canals in Drosophila melanogaster males are surprisingly different from those previously described in females. Mature ring canal walls in males lack actin and appear to derive directly from(More)
Adult stem cells often divide asymmetrically to produce one self-renewed stem cell and one differentiating cell, thus maintaining both populations. The asymmetric outcome of stem cell divisions can be specified by an oriented spindle and local self-renewal signals from the stem cell niche. Here we show that developmentally programmed asymmetric behavior and(More)
The aly, can, mia and sa genes of Drosophila are essential in males both for the G2-meiosis I transition and for onset of spermatid differentiation. Function of all four genes is required for transcription in primary spermatocytes of a suite of spermatid differentiation genes. aly is also required for transcription of the cell cycle control genes cyclin B(More)
Asymmetric division of adult stem cells generates one self-renewing stem cell and one differentiating cell, thereby maintaining tissue homeostasis. A decline in stem cell function has been proposed to contribute to tissue ageing, although the underlying mechanism is poorly understood. Here we show that changes in the stem cell orientation with respect to(More)