Geometry sensing by dendritic cells dictates spatial organization and PGE2-induced dissolution of podosomes

Assembly and disassembly of adhesion structures such as focal adhesions (FAs) and podosomes regulate cell adhesion and differentiation. On antigen-presenting dendritic cells (DCs), acquisition of a migratory and immunostimulatory phenotype depends on podosome dissolution by prostaglandin E(2) (PGE(2)). Whereas the effects of physico-chemical and topographical cues have been extensively studied on FAs, little is known about how podosomes respond to these signals. Here, we show that, unlike for FAs, podosome formation is not controlled by substrate physico-chemical properties. We demonstrate that cell adhesion is the only prerequisite for podosome formation and that substrate availability dictates podosome density. Interestingly, we show that DCs sense 3-dimensional (3-D) geometry by aligning podosomes along the edges of 3-D micropatterned surfaces. Finally, whereas on a 2-dimensional (2-D) surface PGE(2) causes a rapid increase in activated RhoA levels leading to fast podosome dissolution, 3-D geometric cues prevent PGE(2)-mediated RhoA activation resulting in impaired podosome dissolution even after prolonged stimulation. Our findings indicate that 2-D and 3-D geometric cues control the spatial organization of podosomes. More importantly, our studies demonstrate the importance of substrate dimensionality in regulating podosome dissolution and suggest that substrate dimensionality plays an important role in controlling DC activation, a key process in initiating immune responses.     

A genome-wide association study of Hodgkin's lymphoma identifies new susceptibility loci at 2p16.1 (REL), 8q24.21 and 10p14 (GATA3)

To identify susceptibility loci for classical Hodgkin's lymphoma (cHL), we conducted a genome-wide association study of 589 individuals with cHL (cases) and 5,199 controls with validation in four independent samples totaling 2,057 cases and 3,416 controls. We identified three new susceptibility loci at 2p16.1 (rs1432295, REL, odds ratio (OR) = 1.22, combined P = 1.91 × 10(-8)), 8q24.21 (rs2019960, PVT1, OR = 1.33, combined P = 1.26 × 10(-13)) and 10p14 (rs501764, GATA3, OR = 1.25, combined P = 7.05 × 10(-8)). Furthermore, we confirmed the role of the major histocompatibility complex in disease etiology by revealing a strong human leukocyte antigen (HLA) association (rs6903608, OR = 1.70, combined P = 2.84 × 10(-50)). These data provide new insight into the pathogenesis of cHL.     

A genome-wide association scan of tag SNPs identifies a susceptibility variant for colorectal cancer at 8q24.21

Much of the variation in inherited risk of colorectal cancer (CRC) is probably due to combinations of common low risk variants. We conducted a genome-wide association study of 550,000 tag SNPs in 930 familial colorectal tumor cases and 960 controls. The most strongly associated SNP (P = 1.72 x 10(-7), allelic test) was rs6983267 at 8q24.21. To validate this finding, we genotyped rs6983267 in three additional CRC case-control series (4,361 affected individuals and 3,752 controls; 1,901 affected individuals and 1,079 controls; 1,072 affected individuals and 415 controls) and replicated the association, providing P = 1.27 x 10(-14) (allelic test) overall, with odds ratios (ORs) of 1.27 (95% confidence interval (c.i.): 1.16-1.39) and 1.47 (95% c.i.: 1.34-1.62) for heterozygotes and rare homozygotes, respectively. Analyses based on 1,477 individuals with colorectal adenoma and 2,136 controls suggest that susceptibility to CRC is mediated through development of adenomas (OR = 1.21, 95% c.i.: 1.10-1.34; P = 6.89 x 10(-5)). These data show that common, low-penetrance susceptibility alleles predispose to colorectal neoplasia.     

C-terminal truncations in human 3'-5' DNA exonuclease TREX1 cause autosomal dominant retinal vasculopathy with cerebral leukodystrophy

Autosomal dominant retinal vasculopathy with cerebral leukodystrophy is a microvascular endotheliopathy with middle-age onset. In nine families, we identified heterozygous C-terminal frameshift mutations in TREX1, which encodes a 3'-5' exonuclease. These truncated proteins retain exonuclease activity but lose normal perinuclear localization. These data have implications for the maintenance of vascular integrity in the degenerative cerebral microangiopathies leading to stroke and dementias.     

Hotspots of aberrant epigenomic reprogramming in human induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) offer immense potential for regenerative medicine and studies of disease and development. Somatic cell reprogramming involves epigenomic reconfiguration, conferring iPSCs with characteristics similar to embryonic stem (ES) cells. However, it remains unknown how complete the reestablishment of ES-cell-like DNA methylation patterns is throughout the genome. Here we report the first whole-genome profiles of DNA methylation at single-base resolution in five human iPSC lines, along with methylomes of ES cells, somatic cells, and differentiated iPSCs and ES cells. iPSCs show significant reprogramming variability, including somatic memory and aberrant reprogramming of DNA methylation. iPSCs share megabase-scale differentially methylated regions proximal to centromeres and telomeres that display incomplete reprogramming of non-CG methylation, and differences in CG methylation and histone modifications. Lastly, differentiation of iPSCs into trophoblast cells revealed that errors in reprogramming CG methylation are transmitted at a high frequency, providing an iPSC reprogramming signature that is maintained after differentiation.     

Vascular normalization in Rgs5-deficient tumours promotes immune destruction

The vasculature of solid tumours is morphologically aberrant and characterized by dilated and fragile vessels, intensive vessel sprouting and loss of hierarchical architecture. Constant vessel remodelling leads to spontaneous haemorrhages and increased interstitial fluid pressure in the tumour environment. Tumour-related angiogenesis supports tumour growth and is also a major obstacle for successful immune therapy as it prevents migration of immune effector cells into established tumour parenchyma. The molecular mechanisms for these angiogenic alterations are largely unknown. Here we identify regulator of G-protein signalling 5 (Rgs5) as a master gene responsible for the abnormal tumour vascular morphology in mice. Loss of Rgs5 results in pericyte maturation, vascular normalization and consequent marked reductions in tumour hypoxia and vessel leakiness. These vascular and intratumoral changes enhance influx of immune effector cells into tumour parenchyma and markedly prolong survival of tumour-bearing mice. This is the first demonstration, to our knowledge, of reduced tumour angiogenesis and improved immune therapeutic outcome on loss of a vascular gene function and establishes a previously unrecognized role of G-protein signalling in tumour angiogenesis.     

Soma-germline interactions coordinate homeostasis and growth in the Drosophila gonad

The ability of organs such as the liver or the lymphoid system to maintain their original size or regain it after injury is well documented. However, little is known about how these organs sense that equilibrium is breached, and how they cease changing when homeostasis is reached. Similarly, it remains unclear how, during normal development, different cell types within an organ coordinate their growth. Here we show that during gonad development in the fruitfly Drosophila melanogaster the proliferation of primordial germ cells (PGCs) and survival of the somatic intermingled cells (ICs) that contact them are coordinated by means of a feedback mechanism composed of a positive signal and a negative signal. PGCs express the EGF receptor (EGFR) ligand Spitz, which is required for IC survival. In turn, ICs inhibit PGC proliferation. Thus, homeostasis and coordination of growth between soma and germ line in the larval ovary is achieved by using a sensor of PGC numbers (EGFR-mediated survival of ICs) coupled to a correction mechanism inhibiting PGC proliferation. This feedback loop ensures that sufficient numbers of PGCs exist to fill all the stem-cell niches that form at the end of larval development. We propose that similar feedback mechanisms might be generally used for coordinated growth, regeneration and homeostasis.     

The finished DNA sequence of human chromosome 12

Human chromosome 12 contains more than 1,400 coding genes and 487 loci that have been directly implicated in human disease. The q arm of chromosome 12 contains one of the largest blocks of linkage disequilibrium found in the human genome. Here we present the finished sequence of human chromosome 12, which has been finished to high quality and spans approximately 132 megabases, representing approximately 4.5% of the human genome. Alignment of the human chromosome 12 sequence across vertebrates reveals the origin of individual segments in chicken, and a unique history of rearrangement through rodent and primate lineages. The rate of base substitutions in recent evolutionary history shows an overall slowing in hominids compared with primates and rodents.