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The generation of the tubular network of the endoplasmic reticulum (ER) requires homotypic membrane fusion that is mediated by the dynamin-like, membrane-bound GTPase atlastin (ATL). Here, we have determined crystal structures of the cytosolic segment of human ATL1, which give insight into the mechanism of membrane fusion. The structures reveal a GTPase(More)
In mammals, dosage compensation between XX and XY individuals occurs through X chromosome inactivation (XCI). The noncoding Xist RNA is expressed and initiates XCI only when more than one X chromosome is present. Current models invoke a dependency on the X-to-autosome ratio (X:A), but molecular factors remain poorly defined. Here, we demonstrate that(More)
Once protein-coding, the X-inactivation center (Xic) is now dominated by large noncoding RNAs (ncRNA). X chromosome inactivation (XCI) equalizes gene expression between mammalian males and females by inactivating one X in female cells. XCI requires Xist, an ncRNA that coats the X and recruits Polycomb proteins. How Xist is controlled remains unclear but(More)
The homotypic fusion of endoplasmic reticulum (ER) membranes is mediated by atlastin (ATL), which consists of an N-terminal cytosolic domain containing a GTPase module and a three-helix bundle followed by two transmembrane (TM) segments and a C-terminal tail (CT). Fusion depends on a GTP hydrolysis-induced conformational change in the cytosolic domain.(More)
In Drosophila melanogaster, the gene Sex-lethal (Sxl) controls all aspects of female development. Since melanogaster males lacking Sxl appear wild type, Sxl would seem to be functionally female specific. Nevertheless, in insects as diverse as honeybees and houseflies, Sxl seems not to determine sex or to be functionally female specific. Here we describe(More)
The endoplasmic reticulum (ER) is involved in many critical processes, including protein and lipid synthesis and calcium storage. Morphologically, the ER can be divided into two subdomains: a network of interconnected tubules and interspersed sheets. Until recently, how these different compartments form in a continuous membrane system was unclear. Several(More)
X-chromosome inactivation balances X-chromosome dosages in male and female mammals by transcriptionally repressing one X in the female sex. Proper counting and the mutually exclusive choice of active X and inactive X have been hypothesized to involve X-chromosome crosstalk via homologous chromosome pairing. Transient pairing of two female Xs requires(More)
To understand how postmating isolation is connected to the normal process of species divergence and why hybrid male sterility is often the first sign of speciation, we analyzed the Odysseus (OdsH) gene of hybrid male sterility in Drosophila. We carried out expression analysis, transgenic study, and gene knockout. The combined evidence suggests that the(More)
The importance of gene duplication in evolution has long been recognized. Because duplicated genes are prone to diverge in function, gene duplication could plausibly play a role in species differentiation. However, experimental evidence linking gene duplication with speciation is scarce. Here, we show that a hybrid-male sterility gene, Odysseus (OdsH),(More)
Wolbachia is a ubiquitous intracellular endosymbiont of invertebrates. Surprisingly, infection of Drosophila melanogaster by this maternally inherited bacterium restores fertility to females carrying ovarian tumor (cystocyte overproliferation) mutant alleles of the Drosophila master sex-determination gene, Sex-lethal (Sxl). We scanned the Drosophila genome(More)