Intraspecific chromosome variation between different populations ofCtenomys dorbignyi (Rodentia, Ctenomyidae) from Argentina

We used banding techniques to analyze the karyotypes of 17 individuals ofCtenomys dorbignyi Contreras and Contreras, 1984, from populations in Corrientes (Mbarigüí, the type locality, and Sarandicito) belonging to the previously known range of the species, and Entre Ríos (Tiro Federal and Paso Vera) representing a new geographically isolated group of populations. All known populations have 2n=70 although the extreme geographic isolation of the different localities suggested the possibility of chromosomal divergence. We found three different karyomorphs; two of them (Mbarigüí and Sarandicito) had 6 pairs of biarmed autosomes and 28 pairs of telocentric autosomes, with an FN=80. Pair 20 (telocentric) was the carrier of the only detected NOR. However, pair 2 was clearly different in each of these two, being metacentric in Sarandicito and submetacentric in Mbarigüí. The third fixed karyomorph differed significantly from the others, showing 8 pairs of biarmed autosomes and 26 pairs of telocentric autosomes, with an FN=84. Pair 3 (biarmed) was the carrier of the single NOR detected. The NOR carrier also showed a marked heteromorphism (Corrientes vs Entre Ríos) evidenced by differences in the length of the short arm. These observations revealed a chromosomal polytypism that was expected owing to the disjunct geographic distribution of the species.     

Human immunodeficiency virus type 1 nef expression prevents AP-2-mediated internalization of the major histocompatibility complex class II-associated invariant chain

The lentiviral Nef protein has been studied extensively for its ability to induce the downregulation of several immunoreceptors on the surfaces of infected cells. However, Nef expression is unique in inducing highly effective upregulation of the major histocompatibility complex class II-associated chaperone invariant (Ii) chain complexes in different cell types. Under normal conditions, endocytosis of the Ii chain and other molecules, like the transferrin receptor and CD4, is rapid and AP-2 dependent. Human immunodeficiency virus type 1 (HIV-1) Nef expression strongly reduces the internalization of the Ii chain, enhances that of CD4, and does not modify transferrin uptake. The mutation of AP-2 binding motifs LL164 and DD174 in Nef leads to the inhibition of Ii chain upregulation. In AP-2-depleted cells, surface levels of the Ii chain are high and remain unmodified by Nef expression, further indicating that Nef regulates Ii chain internalization via the AP-2 pathway. Immunoprecipitation experiments revealed that the Ii chain can interact with Nef in a dileucine-dependent manner. Importantly, we have shown that Nef-induced CD4 downregulation and Ii chain upregulation are genetically distinguishable. We have identified natural nef alleles that have lost one of the two functions but not the other one. Moreover, we have characterized Nef mutant forms possessing a similar phenotype in the context of HIV-1 infection. Therefore, the Nef-induced accumulation of Ii chain complexes at the cell surface probably results from a complex mechanism leading to the impairment of AP-2-mediated endocytosis rather than from direct competition between Nef and the Ii chain for binding AP-2.     

Theta defensins protect cells from infection by herpes simplex virus by inhibiting viral adhesion and entry

We tested the ability of 20 synthetic theta defensins to protect cells from infection by type 1 and type 2 herpes simplex viruses (HSV-1 and -2, respectively). The peptides included rhesus theta defensins (RTDs) 1 to 3, originally isolated from rhesus macaque leukocytes, and three peptides (retrocyclins 1 to 3) whose sequences were inferred from human theta-defensin (DEFT) pseudogenes. We also tested 14 retrocyclin analogues, including the retro, enantio, and retroenantio forms of retrocyclin 1. Retrocyclins 1 and 2 and RTD 3 protected cervical epithelial cells from infection by both HSV serotypes, but only retrocyclin 2 did so without causing cytotoxicity or requiring preincubation with the virus. Surface plasmon resonance studies revealed that retrocyclin 2 bound to immobilized HSV-2 glycoprotein B (gB2) with high affinity (K(d), 13.3 nM) and that it did not bind to enzymatically deglycosylated gB2. Temperature shift experiments indicated that retrocyclin 2 and human alpha defensins human neutrophil peptide 1 (HNP 1) to HNP 3 protected human cells from HSV-2 by different mechanisms. Retrocyclin 2 blocked viral attachment, and its addition during the binding or penetration phases of HSV-2 infection markedly diminished nuclear translocation of VP16 and expression of ICP4. In contrast, HNPs 1 to 3 had little effect on binding but reduced both VP16 transport and ICP4 expression if added during the postbinding (penetration) period. We recently reported that theta defensins are miniature lectins that bind gp120 of human immunodeficiency virus type 1 (HIV-1) with high affinity and inhibit the entry of R5 and X4 isolates of HIV-1. Given its small size (18 residues), minimal cytotoxicity, lack of activity against vaginal lactobacilli, and effectiveness against both HSV-2 and HIV-1, retrocyclin 2 provides an intriguing prototype for future topical microbicide development.     

A set of BAC clones spanning the human genome

Using the human bacterial artificial chromosome (BAC) fingerprint-based physical map, genome sequence assembly and BAC end sequences, we have generated a fingerprint-validated set of 32855 BAC clones spanning the human genome. The clone set provides coverage for at least 98% of the human fingerprint map, 99% of the current assembled sequence and has an effective resolving power of 79 kb. We have made the clone set publicly available, anticipating that it will generally facilitate FISH or array-CGH-based identification and characterization of chromosomal alterations relevant to disease.     

A recovery story that heals

It is one thing to talk about intergenerational trauma and substance abuse in general terms, and quite another to get an experiential sense of what it is like for someone dealing with it firsthand. In a profoundly courageous presentation, Mabel Kudralook Smith, who is originally from Barrow, presents her personal story. She takes to heart the notion that to heal, you have to talk about those matters that are causing you pain. Such accounts are healing because they allow the storyteller to pull together a coherent narrative that helps make sense of what she or he has experienced. The narratives often provide a sense of release as the teller is no longer expending energy on keeping personal or family secrets and being ashamed. Such stories are also healing for the audience, because they allow others, through the sharing of experience, to better understand what the speaker has endured and learned. If the listeners have faced similar issues, the narratives can inspire them to embark on or persist in their own similar journies.     

Human immunodeficiency virus-1 Nef expression induces intracellular accumulation of multivesicular bodies and major histocompatibility complex class II complexes: potential role of phosphatidylinositol 3-kinase

Nef alters the cell surface expression of several immunoreceptors, which may contribute to viral escape. We show that Nef modifies major histocompatibility complex class II (MHC II) intracellular trafficking and thereby its function. In the presence of Nef, mature, peptide-loaded MHC II were down-modulated at the cell surface and accumulated intracellularly, whereas immature (invariant [Ii] chain-associated) MHC II expression at the plasma membrane was increased. Antibody internalization experiments and subcellular fractionation analyses showed that immature MHC II were internalized from the plasma membrane but had limited access to lysosomes, explaining the reduced Ii chain degradation. Immunoelectron microscopy revealed that Nef expression induced a marked accumulation of multivesicular bodies (MVBs) containing Nef, MHC II, and high amounts of Ii chain. The Nef-induced up-regulation of surface Ii chain was inhibited by LY294002 exposure, indicating the involvement of a phosphatidylinositol 3-kinase, whose products play a key role in MVB biogenesis. Together, our results indicate that Nef induces an increase of the number of MVBs where MHC II complexes accumulate. Given that human immunodeficiency virus recruits the MVB machinery for its assembly process, our data raise the possibility that Nef is involved in viral assembly through its effect on MVBs.     

Inactivation of the Huntington's disease gene (Hdh) impairs anterior streak formation and early patterning of the mouse embryo

Background

Delta, Notch, and Scabrous often function together to make different cell types and refine tissue patterns during Drosophila development. Delta is known as the ligand that triggers Notch receptor activity. Scabrous is known to bind Notch and promote Notch activity in response to Delta. It is not known if Scabrous binds Delta or Delta has activity other than its activity as a ligand of Notch. It is very difficult to clearly determine this binding or activity in vivo as all Notch, Delta, and Scabrous activities are required simultaneously or successively in an inter-dependent manner.

Results

Using Drosophila cultured cells we show that the full length Delta promotes accumulation of Daughterless protein, fringe RNA, and pangolin RNA in the absence of Scabrous or Notch. Scabrous binds Delta and suppresses this activity even though it increases the level of the Delta intracellular domain. We also show that Scabrous can promote Notch receptor activity, in the absence of Delta.

Conclusion

Delta has activity that is independent of its activity as a ligand of Notch. Scabrous suppresses this Delta activity. Scabrous also promotes Notch activity that is dependent on Delta's ligand activity. Thus, Notch, Delta, and Scabrous might function in complex combinatorial or mutually exclusive interactions during development. The data reported here will be of significant help in understanding these interactions in vivo.     

Novel innate immune functions for galectin-1: galectin-1 inhibits cell fusion by Nipah virus envelope glycoproteins and augments dendritic cell secretion of proinflammatory cytokines

Galectin-1 (gal-1), an endogenous lectin secreted by a variety of cell types, has pleiotropic immunomodulatory functions, including regulation of lymphocyte survival and cytokine secretion in autoimmune, transplant disease, and parasitic infection models. However, the role of gal-1 in viral infections is unknown. Nipah virus (NiV) is an emerging pathogen that causes severe, often fatal, febrile encephalitis. The primary targets of NiV are endothelial cells. NiV infection of endothelial cells results in cell-cell fusion and syncytia formation triggered by the fusion (F) and attachment (G) envelope glycoproteins of NiV that bear glycan structures recognized by gal-1. In the present study, we report that NiV envelope-mediated cell-cell fusion is blocked by gal-1. This inhibition is specific to the Paramyxoviridae family because gal-1 did not inhibit fusion triggered by envelope glycoproteins of other viruses, including two retroviruses and a pox virus, but inhibited fusion triggered by envelope glycoproteins of the related Hendra virus and another paramyxovirus. The physiologic dimeric form of gal-1 is required for fusion inhibition because a monomeric gal-1 mutant had no inhibitory effect on cell fusion. gal-1 binds to specific N-glycans on NiV glycoproteins and aberrantly oligomerizes NiV-F and NiV-G, indicating a mechanism for fusion inhibition. gal-1 also increases dendritic cell production of proinflammatory cytokines such as IL-6, known to be protective in the setting of other viral diseases such as Ebola infections. Thus, gal-1 may have direct antiviral effects and may also augment the innate immune response against this emerging pathogen.