Using genome-wide data from 253,288 individuals, we identified 697 variants at genome-wide significance that together explain one-fifth of heritability for adult height. By testing different numbers of variants in independent studies, we show that the most strongly associated ~2,000, ~3,700 and ~9,500 SNPs explained ~21%, ~24% and ~29% of phenotypic variance. Furthermore, all common variants together captured the majority (60%) of heritability. The 697 variants clustered in 423 loci enriched for genes, pathways, and tissue-types known to be involved in growth and together implicated genes and pathways not highlighted in earlier efforts, such as signaling by fibroblast growth factors, WNT/beta-catenin, and chondroitin sulfate-related genes. We identified several genes and pathways not previously connected with human skeletal growth, including mTOR, osteoglycin and binding of hyaluronic acid. Our results indicate a genetic architecture for human height that is characterized by a very large but finite number (thousands) of causal variants.

Although Akt is known as a survival kinase, inhibitors of the phosphatidylinositol 3-kinase (PI3K)–Akt pathway do not always induce substantial apoptosis. We show that silencing Akt1 alone, or any combination of Akt isoforms, can suppress the growth of tumors established from phosphatase and tensin homologue–null human cancer cells. Although these findings indicate that Akt is essential for tumor maintenance, most tumors eventually rebound. Akt knockdown or inactivation with small molecule inhibitors did not induce significant apoptosis but rather markedly increased autophagy. Further treatment with the lysosomotropic agent chloroquine caused accumulation of abnormal autophagolysosomes and reactive oxygen species, leading to accelerated cell death in vitro and complete tumor remission in vivo. Cell death was also promoted when Akt inhibition was combined with the vacuolar H+–adenosine triphosphatase inhibitor bafilomycin A1 or with cathepsin inhibition. These results suggest that blocking lysosomal degradation can be detrimental to cancer cell survival when autophagy is activated, providing rationale for a new therapeutic approach to enhancing the anticancer efficacy of PI3K–Akt pathway inhibition.

We have used (cryo) electron tomography to provide a 3-dimensional (3D) map of the intracellular membrane organization of human platelets at high spatial resolution. Our study shows that the open canalicular system and dense tubular system are highly intertwined and form close associations in specialized membrane regions. 3D reconstructions of individual ␣-granules revealed large heterogeneity in their membrane organization. On the basis of their divergent morphology, we categorized ␣-granules into the following subtypes: spherical granules with electron-dense and electron-lucent zone containing 12-nm von Willebrand factor tubules, subtypes containing a multitude of luminal vesicles, 50-nm-wide tubular organelles, and a population with 18.4-nm crystalline cross-striations. Low-dose (cryo) electron tomography and 3D reconstruction of whole vitrified platelets confirmed the existence of long tubular granules with a remarkably curved architecture. Immunoelectron microscopy confirmed that these extended structures represent ␣-granule subtypes. Tubular ␣-granules represent approximately 16% of the total ␣-granule population and are detected in approximately half of the platelet population. They express membrane-bound proteins GLUT3 and ␣IIb-␤3 integrin and contain abundant fibrinogen and albumin but low levels of ␤-thromboglobulin and no von Willebrand factor. Our 3D study demonstrates that, besides the existence of morphologically different ␣-granule subtypes, high spatial segregation of cargo exists within individual ␣-granules. (Blood. 2010;116(7):1147-1156) IntroductionBlood platelets are the smallest cells in our circulation. They play a central role in the arrest of bleeding after damage of a blood vessel and are crucial elements in the development of thrombosis. 1,2 On injury, platelets rapidly adhere to components of the subendothelium, followed by shape change and subsequent granule secretion. 3 These rapid membrane dynamics are crucial for the progression of platelet-substrate interaction (spreading) and subsequent plateletplatelet interaction (aggregation), ultimately leading to the formation of a platelet plug and the arrest of bleeding. 4 Platelets contain several distinct membrane systems: (1) the open canalicular system (OCS), which is continuous with the cell surface and serves as a membrane reservoir during shape change and spreading 5,6 ; (2) the dense tubular system (DTS), representing the platelet smooth endoplasmic reticulum 7 ; and (3) secretory organelles. Four types of secretory organelles have been identified in platelets, based on their ultrastructure and selective protein composition: ␣-granules, dense granules, multivesicular bodies, and lysosomes. 8-10 ␣-Granules are the major secretory organelles and appear in electron microscopy cross sections as 200-to 500-nm spherical organelles. Platelet ␣-granules and dense granules are differentially released and play crucial roles in the secondary platelet response. 11,12 Recent studies have suggested the existence of ␣-granule subclasses with dif...

Like several other intracellular pathogens, Mycobacterium marinum (Mm) escapes from phagosomes into the host cytosol where it can polymerize actin, leading to motility that promotes spread to neighboring cells. However, only ∼25% of internalized Mm form actin tails, and the fate of the remaining bacteria has been unknown. Here we show that cytosolic access results in a new and intricate host pathogen interaction: host macrophages ubiquitinate Mm, while Mm shed their ubiquitinated cell walls. Phagosomal escape and ubiquitination of Mm occured rapidly, prior to 3.5 hours post infection; at the same time, ubiquitinated Mm cell wall material mixed with host-derived dense membrane networks appeared in close proximity to cytosolic bacteria, suggesting cell wall shedding and association with remnants of the lysed phagosome. At 24 hours post-infection, Mm that polymerized actin were not ubiquitinated, whereas ubiquitinated Mm were found within LAMP-1–positive vacuoles resembling lysosomes. Though double membranes were observed which sequestered Mm away from the cytosol, targeting of Mm to the LAMP-1–positive vacuoles was independent of classical autophagy, as demonstrated by absence of LC3 association and by Atg5-independence of their formation. Further, ubiquitination and LAMP-1 association did not occur with mutant avirulent Mm lacking ESX-1 (type VII) secretion, which fail to escape the primary phagosome; apart from its function in phagosome escape, ESX-1 was not directly required for Mm ubiquitination in macrophages or in vitro. These data suggest that virulent Mm follow two distinct paths in the cytosol of infected host cells: bacterial ubiquitination is followed by sequestration into lysosome-like organelles via an autophagy-independent pathway, while cell wall shedding may allow escape from this fate to permit continued residence in the cytosol and formation of actin tails.

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