Deletion of the pluripotency-associated Tex19.1 gene causes activation of endogenous retroviruses and defective spermatogenesis in mice

As genetic information is transmitted through successive generations, it passes between pluripotent cells in the early embryo and germ cells in the developing foetus and adult animal. Tex19.1 encodes a protein of unknown function, whose expression is restricted to germ cells and pluripotent cells. During male spermatogenesis, Tex19.1 expression is highest in mitotic spermatogonia and diminishes as these cells differentiate and progress through meiosis. In pluripotent stem cells, Tex19.1 expression is also downregulated upon differentiation. However, it is not clear whether Tex19.1 has an essential function in germ cells or pluripotent stem cells, or what that function might be. To analyse the potential role of Tex19.1 in pluripotency or germ cell function we have generated Tex19.1(-/-) knockout mice and analysed the Tex19.1(-/-) mutant phenotype. Adult Tex19.1(-/-) knockout males exhibit impaired spermatogenesis. Immunostaining and histological analysis revealed defects in meiotic chromosome synapsis, the persistence of DNA double-strand breaks during meiosis, and a loss of post-meiotic germ cells in the testis. Furthermore, expression of a class of endogenous retroviruses is upregulated during meiosis in the Tex19.1(-/-) testes. Increased transposition of endogenous retroviruses in the germline of Tex19.1(-/-) mutant mice, and the concomitant increase in DNA damage, may be sufficient to disrupt the normal processes of recombination and chromosome synapsis during meiosis and cause defects in spermatogenesis. Our results suggest that Tex19.1 is part of a specialised mechanism that operates in the germline to repress transposable genetic elements and maintain genomic stability through successive generations.     

Synergistic anti‐proliferative and pro‐apoptotic activity of combined therapy with bortezomib,a proteasome inhibitor,with anti‐epidermal growth factor receptor (EGFR) drugs in human cancer cells

The article to which this erratum refers was published in J Cell Physiol (2008) 216: 698–707. © 2008 Wiley‐Liss, Inc. DOI: 10.1002/jcp.21444     

Modeling balance control during sustained waking allows posturographic sleepiness testing

We develop a method to quantify sleepiness. Sleepiness is a major risk factor in traffic and occupational accidents, but lack of convenient tests precludes monitoring impending sleepiness. Posturographic balance testing could address this need because sleepiness increases postural sway. It is, however, unclear how sleepiness influences balance control. Our results, for 12 subjects, show that balance control is more susceptible to increasing time awake (TA) compared to neuromuscular processes. This conclusion is reached since during sustained waking the control process slows down by 3.4% per hour of increased TA. This slowdown accounts for 65% of the variance in diurnal balance. We quantified balance control by modeling the body as an inverted pendulum and by expressing the control as the critical time interval for open-loop control (Deltat(c)) of the center-of-mass movements of this pendulum. To estimate the subjects' TA, we regressed the Deltat(c) scores recorded during sustained waking against increasing TA, and equated separate Deltat(c) test scores with the diurnal Deltat(c) scores. We estimated TA with 68% positive predictive value. The results encourage implementing balance modeling into a device that performs clinical or industrial balance testing because the model-based Deltat(c) score responded to increasing TA.     

MAGE-A3<Subscript>161–175 </Subscript>contains an HLA-DRβ4 restricted natural epitope poorly formed through indirect presentation by dendritic cells

We report here that HLA-DRβ4*01 restricted MAGE-A3_161–175 specific CD4⁺ T cells from a healthy donor recognize a naturally processed epitope formed through the exogenous but not the endogenous pathway. However, the intensity of recognition of the native epitope by MAGE-A3_161–175 specific CD4⁺ T cells strongly depends on the antigen presenting cells and the amount of protein available for processing. EBV-transformed lymphoblastoid cells (LCLs) and melanoma cells engineered to express MAGE-A3 in the endosomal/lysosomal compartment were strongly recognized while autologous dendritic cells loaded with lysate from MAGE-A3 expressing cells were, although significantly, poorly recognized. To prove that the amount of antigen available for processing was a key factor determining the different response LCLs were sorted by MAGE-A3 expression. The response intensity correlated with the amount of MAGE-A3 expressed by the cells. Collectively, these results suggest that different antigen presenting cells with different amount of antigen available for processing as well as protease activity are important factors in determining the epitope repertoire produced in vivo, and therefore reliable tools should be used when testing recognition of native epitopes by peptide specific CD4⁺ T cells.     

Exploring the effects of gene dosage on mandible shape in mice as a model for studying the genetic basis of natural variation

Mandible shape in the mouse is a complex trait that is influenced by many genetic factors. However, little is known about the action of single genes on adult mandible shape so far, since most developmentally relevant genes are already required during embryogenesis, i.e., knockouts lead to embryonic death or severe deformations, before the mandible is fully formed. We employ here a geometric morphometric approach to identify subtle phenotypic differences caused by dosage effects of candidate genes. We use mouse strains with specific gene modifications (knockouts and knockins) to compare heterozygous animals with controls from the same stock, which is expected to be equivalent to a change of gene expression of the respective locus. Such differences in expression level are also likely to occur as part of the natural variation. We focus on Bmp pathway genes (Bmp4, its antagonist Noggin, and combinations of Bmp5-7 genotypes), but include also two other developmental control genes suspected to affect mandible development in some way (Egfr and Irf6). In addition, we study the effects of Hoxd13, as well as an extracellular matrix constituent (Col2a1). We find that subtle but significant shape differences are caused by differences in gene dosage of several of these genes. The changes seen for Bmp4 and Noggin are partially compatible with the action of these genes known from birds and fish. We find significant shape changes also for Hoxd13, although this gene has so far only been implicated in skeletal patterning processes of the limbs. Comparing the effect sizes of gene dosage changes to the variation found in natural populations of mice as well as quantitative trait loci (QTL) effects on mandible shape, we find that the effect sizes caused by gene dosage changes are at the lower end of the spectrum of natural variation, but larger than the average additive effects found in QTL studies. We conclude that studying gene dosage effects have the potential to provide new insights into aspects of craniofacial development, variation, and evolution.     

Higher Prevalence and Abundance of Bdellovibrio bacteriovorus in the Human Gut of Healthy Subjects

Introduction

Members of the human intestinal microbiota are key players in maintaining human health. Alterations in the composition of gut microbial community (dysbiosis) have been linked with important human diseases. Understanding the underlying processes that control community structure, including the bacterial interactions within the microbiota itself, is essential. Bdellovibrio bacteriovorus is a gram-negative bacterium that preys other gram-negative species for survival, acting as a population-balancer. It was found in terrestrial/aquatic ecosystems, and in animal intestines, postulating its presence also in the human gut.

Methods

The present study was aimed to evaluate, by end-point PCR and qPCR, the presence of B. bacteriovorus in intestinal and faecal biopsy specimens from 92 paediatric healthy subjects and patients, suffering from Inflammatory Bowel Diseases (IBD), Celiac disease and Cystic fibrosis (CF).

Results

i) B. bacteriovorus was present and abundant only in healthy individuals, while it was heavily reduced in patients, as in the case of IBD and Celiac, while in CF patients and relative controls we observed comparable results; ii) B. bacteriovorus seemed to be mucosa-associated, because all IBD and Celiac biopsies (and related controls) were treated with mucus-removing agents, leaving only the mucosa-attached microflora; iii) B. bacteriovorus abundance was district-dependent, with a major preponderance in duodenum, and gradually decreasing up to rectum; iv) B. bacteriovorus levels significantly dropped in disease status, in duodenum and ileum.

Conclusions

Results obtained in this study could represent the first step for new therapeutic strategies aimed to restore a balance in the intestinal ecosystem, utilizing Bdellovibrio as a probiotic.     

Validation of a microsatellite panel for parentage testing of locally adapted and commercial goats in Brazil

Brazilian goats are generally kept in small herds and extensive rearing systems, mainly in the northeastern region of the country. Despite production improvement in recent years, the lack of pedigree control has affected genetic progress. This study aimed to validate a panel of 16 microsatellites for parentage testing in locally adapted and commercial goats breeds raised in Brazil, as well as to compare its efficiency with the panel recommended by the Brazilian Ministry of Agriculture, Livestock and Supplies (MAPA) in 2004. The number of alleles and expected heterozygosity (He) per marker ranged from four to 18, and from 0.051 to 0.831, respectively. Using all markers, 100% of parentage cases of the validation dataset were resolved with a strict confidence level of 95%. The 16 microsatellites panel showed adequate exclusion power (99.99%) and identity accuracy (99.99%). Suggestions for improvement of the marker panel endorsed by MAPA are provided.     

The Saccharomyces cerevisiae Sae2 protein negatively regulates DNA damage checkpoint signalling

Double-strand breaks (DSBs) elicit a DNA damage response, resulting in checkpoint-mediated cell-cycle delay and DNA repair. The Saccharomyces cerevisiae Sae2 protein is known to act together with the MRX complex in meiotic DSB processing, as well as in DNA damage response during the mitotic cell cycle. Here, we report that cells lacking Sae2 fail to turn off both Mec1- and Tel1-dependent checkpoints activated by a single irreparable DSB, and delay Mre11 foci disassembly at DNA breaks, indicating that Sae2 may negatively regulate checkpoint signalling by modulating MRX association at damaged DNA. Consistently, high levels of Sae2 prevent checkpoint activation and impair MRX foci formation in response to unrepaired DSBs. Mec1- and Tel1-dependent Sae2 phosphorylation is necessary for these Sae2 functions, suggesting that the two kinases, once activated, may regulate checkpoint switch off through Sae2-mediated inhibition of MRX signalling.