The rockefeller university

Kaposi sarcoma (KS) is an endothelial malignancy caused by human herpes virus-8 (HHV-8) infection. The epidemic and iatrogenic forms of childhood KS result from a profound and acquired T cell deficiency. Recent studies have shown that classic KS of childhood can result from rare single-gene inborn errors of immunity, with mutations in WAS, IFNGR1, STIM1, and TNFRSF4. The pathogenesis of the endemic form of childhood KS has remained elusive. We review childhood KS pathogenesis and its relationship to inherited and acquired immunodeficiency to oncogenic HHV-8.

The transcription factor Blimp-1 is necessary for the generation of plasma cells. Here we studied its functions in plasmablast differentiation by identifying regulated Blimp-1 target genes. Blimp-1 promoted the migration and adhesion of plasmablasts. It directly repressed genes encoding several transcription factors and Aicda (which encodes the cytidine deaminase AID) and thus silenced B cell specific gene expression, antigen presentation and class-switch recombination in plasmablasts. It directly activated genes, which led to increased expression of the plasma cell regulator IRF4 and proteins involved in immunoglobulin secretion. Blimp-1 induced the transcription of immunoglobulin genes by controlling the 3' enhancers of the loci encoding the immunoglobulin heavy chain (Igh) and K-light chain (lgk) and, furthermore, regulated the post-transcriptional expression switch from the membrane-bound form of the immunoglobulin heavy chain to its secreted form by activating EII2 (which encodes the transcription-elongation factor ELL2). Notably, Blimp-1 recruited chromatin-remodeling and histone-modifying complexes to regulate its target genes. Hence, many essential functions of plasma cells are under the control of Blimp-1.

Deficiency of FANCD2/FANCI-associated nuclease 1 (FAN1) in humans leads to karyomegalic interstitial nephritis (KIN), a rare hereditary kidney disease characterized by chronic renal fibrosis, tubular degeneration, and characteristic polyploid nuclei in multiple tissues. The mechanism of how FAN1 protects cells is largely unknown but is thought to involve FAN1's function in DNA interstrand cross-link (ICL) repair. Here, we describe a Fan1-deficient mouse and show that FAN1 is required for cellular and organismal resistance to ICLs. We show that the ubiquitin-binding zinc finger (UBZ) domain of FAN1, which is needed for interaction with FANCD2, is not required for the initial rapid recruitment of FAN1 to ICLs or for its role in DNA ICL resistance. Epistasis analyses reveal that FAN1 has cross-link repair activities that are independent of the Fanconi anemia proteins and that this activity is redundant with the 5'-3' exonuclease SNM1A. Karyomegaly becomes prominent in kidneys and livers of Fan1-deficient mice with age, and mice develop liver dysfunction. Treatment of Fan1-deficient mice with ICL-inducing agents results in pronounced thymic and bone marrow hypocellularity and the disappearance of c-kit(+) cells. Our results provide insight into the mechanism of FAN1 in ICL repair and demonstrate that the Fan1 mouse model effectively recapitulates the pathological features of human FAN1 deficiency.

Here, we screened a 10,371 library of diverse molecules using a drug-sensitive fission yeast strain to identify compounds which cause defects in chromosome segregation during mitosis. We identified a phosphorium-ylide-based compound Cutin-1 which inhibits nuclear envelope expansion and nuclear elongation during the closed mitosis of fission yeast, and showed that its target is the a-subunit of fatty acid synthase. A point mutation in the dehydratase domain of Fas1 conferred in vivo and in vitro resistance to Cutin-1. Time-lapse photomicrography showed that the bulk of the chromosomes were only transiently separated during mitosis, and nucleoli separation was defective. Subsequently sister chromatids re-associated leading to chromosomal mis-segregation. These segregation defects were reduced when the nuclear volume was increased and were increased when the nuclear volume was reduced. We propose that there needs to be sufficient nuclear volume to allow the nuclear elongation necessary during a closed mitosis to take place for proper chromosome segregation, and that inhibition of fatty acid synthase compromises nuclear elongation and leads to defects in chromosomal segregation.

BackgroundThe endocannabinoid system has been found to play an important role in modulating alcohol intake. Inhibition or genetic deletion of fatty acid amide hydrolase (FAAH; a key catabolic enzyme for endocannabinoids) leads to increased alcohol consumption and preference in rodent models. A common human single-nucleotide polymorphism (SNP; C385A, rs324420) in the FAAH gene is associated with decreased enzymatic activity of FAAH, resulting in increased anandamide levels in both humans and FAAH C385A knock-in mice. MethodsAs this FAAH SNP has been reported to be associated with altered alcohol abuse, the present study used these genetic knock-in mice containing the human SNP C385A to determine the impact of variant FAAH gene on alcohol binge drinking in the drinking-in-the-dark (DID) model. ResultsWe found that the FAAH(A/A) mice had greater alcohol intake and preference than the wild-type FAAH(C/C) mice, suggesting that increased endocannabinoid signaling in FAAH(A/A) mice led to increased alcohol binge consumption. The specificity on alcohol vulnerability was suggested by the lack of any FAAH genotype difference on sucrose or saccharin intake. Using the binge DID model, we confirmed that selective CB1 receptor antagonist AM251 reduced alcohol intake in the wild-type mice. ConclusionsThese data suggest that there is direct and selective involvement of the human FAAH C385A SNP and CB1 receptors in alcohol binge drinking.

Faces contain a variety of information such as one's identity and expression. One prevailing model suggests a functional division of labor in processing faces that different aspects of facial information are processed in anatomically separated and functionally encapsulated brain regions. Here, we demonstrate that facial identity and expression can be processed in the same region, yet with different neural coding strategies. To this end, we employed functional magnetic resonance imaging to examine two types of coding schemes, namely univariate activity and multivariate pattern, in the posterior superior temporal cortex (pSTS) - a face-selective region that is traditionally viewed as being specialized for processing facial expression. With the individual difference approach, we found that participants with higher overall face selectivity in the right pSTS were better at differentiating facial expressions measured outside of the scanner. In contrast, individuals whose spatial pattern for faces in the right pSTS was less similar to that for objects were more accurate in identifying previously presented faces. The double dissociation of behavioral relevance between overall neural activity and spatial neural pattern suggests that the functional-division-of-labor model on face processing is over-simplified, and that coding strategies shall be incorporated in a revised model.

Self-renewal is a hallmark of both hematopoietic stem cells (HSCs) and leukemia stem cells (LSCs); therefore, the identification of mechanisms that are required for LSC, but not HSC, function could provide therapeutic opportunities that are more effective and less toxic than current treatments. Here, we employed an in vivo shRNA screen and identified jumonji domain-containing protein JMJD1C as an important driver of MLL-AF9 leukemia. Using a conditional mouse model, we showed that loss of JMJD1C substantially decreased LSC frequency and caused differentiation of MLL-AF9- and homeobox A9-driven (HOXA9-driven) leukemias. We determined that JMJU1C directly interacts with HOXA9 and modulates a HOXA9-controlled gene-expression program. In contrast, loss of JMJD1C led to only minor defects in blood homeostasis and modest effects on HSC self-renewal. Together, these data establish JMJD1C as an important mediator of MLL-AF9- and HOXA9-driven LSC function that is largely dispensable for HSC function.

Actin is one of the most conserved eukaryotic proteins. It is thought to have multiple essential cellular roles and to function primarily or exclusively as filaments ("F-actin"). Chlamydomonas has been an enigma, because a null mutation (ida5-1) in its single gene for conventional actin does not affect growth. A highly divergent actin gene, NAP1, is upregulated in ida5-1 cells, but it has been unclear whether NAP1 can form filaments or provide actin function. Here, we used the actin-depolymerizing drug latrunculin B (LatB), the F-actin-specific probe Lifeact-Venus, and genetic and molecular methods to resolve these issues. LatB-treated wild-type cells continue to proliferate; they initially lose Lifeact-stained structures but recover them concomitant with upregulation of NAP1. Thirty-nine LatB-sensitive mutants fell into four genes (NAP1 and LAT1-LAT3) in which we identified the causative mutations using a novel combinatorial pool-sequencing strategy. LAT1-LAT3 are required for NAP1 upregulation upon LatB treatment, and ectopic expression of NAP1 largely rescues the LatB sensitivity of the lat1-lat3 mutants, suggesting that the LAT gene products comprise a regulatory hierarchy with NAP1 expression as the major functional output. Selection of LatB-resistant revertants of a nap1 mutant yielded dominant IDA5 mutations that presumably render F-IDA5 resistant to LatB, and nap1 and lat mutations are synthetically lethal with ida5-1 in the absence of LatB. We conclude that both IDA5 and the divergent NAP1 can form filaments and redundantly provide essential F-actin functions and that a novel surveillance system, probably responding to a loss of F-actin, triggers NAP1 expression and perhaps other compensatory responses.

The machinery at the eukaryotic replication fork has seen many new structural advances using electron microscopy and crystallography. Recent structures of eukaryotic replisome components include the Mcm2-7 complex, the CMG helicase, DNA polymerases, a Ctf4 trimer hub and the first look at a core replisome of 20 different proteins containing the helicase, primase, leading polymerase and a lagging strand polymerase. The eukaryotic core replisome shows an unanticipated architecture, with one polymerase sitting above the helicase and the other below. Additionally, structures of Mcm2 bound to an H3/H4 tetramer suggest a direct role of the replisome in handling nucleosomes, which are important to DNA organization and gene regulation. This review provides a summary of some of the many recent advances in the structure of the eukaryotic replisome.

Bacterial species comprise related genotypes that can display divergent phenotypes with important clinical implications. Staphylococcus epidermidis is a common cause of nosocomial infections and, critical to its pathogenesis, is its ability to adhere and form biofilms on surfaces, thereby moderating the effect of the host's immune response and antibiotics. Commensal S. epidermidis populations are thought to differ from those associated with disease in factors involved in adhesion and biofilm accumulation. We quantified the differences in biofilm formation in 98 S. epidermidis isolates from various sources, and investigated population structure based on ribosomal multilocus typing (rMLST) and the presence/absence of genes involved in adhesion and biofilm formation. All isolates were able to adhere and form biofilms in in vitro growth assays and confocal microscopy allowed classification into 5 biofilm morphotypes based on their thickness, biovolume and roughness. Phylogenetic reconstruction grouped isolates into three separate clades, with the isolates in the main disease associated clade displaying diversity in morphotype. Of the biofilm morphology characteristics, only biofilm thickness had a significant association with clade distribution. The distribution of some known adhesion-associated genes (aap and sesE) among isolates showed a significant association with the species clonal frame. These data challenge the assumption that biofilm-associated genes, such as those on the ica operon, are genetic markers for less invasive S. epidermidis isolates, and suggest that phenotypic characteristics, such as adhesion and biofilm formation, are not fixed by clonal descent but are influenced by the presence of various genes that are mobile among lineages.