Meiotic and epigenetic defects in Dnmt3L-knockout mouse spermatogenesis

The production of mature germ cells capable of generating totipotent zygotes is a highly specialized and sexually dimorphic process. The transition from diploid primordial germ cell to haploid spermatozoa requires genome-wide reprogramming of DNA methylation, stage- and testis-specific gene expression, mitotic and meiotic division, and the histone-protamine transition, all requiring unique epigenetic control. Dnmt3L, a DNA methyltransferase regulator, is expressed during gametogenesis, and its deletion results in sterility. We found that during spermatogenesis, Dnmt3L contributes to the acquisition of DNA methylation at paternally imprinted regions, unique nonpericentric heterochromatic sequences, and interspersed repeats, including autonomous transposable elements. We observed retrotransposition of an LTR-ERV1 element in the DNA from Dnmt3L(-/-) germ cells, presumably as a result of hypomethylation. Later in development, in Dnmt3L(-/-) meiotic spermatocytes, we detected abnormalities in the status of biochemical markers of heterochromatin, implying aberrant chromatin packaging. Coincidentally, homologous chromosomes fail to align and form synaptonemal complexes, spermatogenesis arrests, and spermatocytes are lost by apoptosis and sloughing. Because Dnmt3L expression is restricted to gonocytes, the presence of defects in later stages reveals a mechanism whereby early genome reprogramming is linked inextricably to changes in chromatin structure required for completion of spermatogenesis.

Glucose affects monocarboxylate cotransporter (MCT) 1 expression during mouse preimplantation development

Cleavage-stage embryos have an absolute requirement for pyruvate and lactate, but as the morula compacts, it switches to glucose as the preferred energy source to fuel glycolysis. Substrates such as glucose, amino acids, and lactate are moved into and out of cells by facilitated diffusion. in the case of lactate and pyruvate, this occurs via H+-monocarboxylate cotransporter (MCT) proteins. To clarify the role of MCT in development, transport characteristics for DL-lactate were examined, as were mRNA expression and protein localisation for MCT1 and MCT3, using confocal laser scanning immunofluorescence in freshly collected and cultured embryos. Blastocysts demonstrated significantly higher affinity for DL-lactate than zygotes (K-m 20 +/- 10 vs 87 +/- 35 mmol lactate/l; P = 0.03 by linear regression) but was similar for all stages. For embryos derived in vivo and those cultured with glucose, MCT1 mRNA was present throughout preimplantation development, protein immunoreactivity appearing diffuse throughout the cytoplasm with brightest intensity in the outer cortical region of blastomeres. in expanding blastocysts, MCT1 became more prominent in the cytoplasmic cortex of blastomeres, with brightest intensity in the polar trophectoderm. Without glucose, MCT1 mRNA was not expressed, and immunoreactivity dramatically reduced in intensity as morulae died. MCT3 mRNA and immunoreactivity were not detected in early embryos. The differential expression of MCT1 in the presence or absence of glucose demonstrates that it is important in the critical regulation of pH and monocarboxylate transport during preimplantation development, and implies a role for glucose in the control of MCT1, but not MCT3, expression.

Mapping the I-3 gene for resistance to Fusarium wilt in tomato: application of an I-3 marker in tomato improvement and progress towards the cloning of I-3

Fusarium wilt of tomato, caused by the fungal pathogen, Fusarium oxysporum f. sp. lycopersici (Fol), is an economically damaging disease that results in huge losses in Australia and other countries worldwide. The I-3 gene, which confers resistance to Fol race 3, has been described in wild tomato, Lycopersicon pennellii, accessions LA716 and PI414773. We are pursuing the isolation of I-3 from LA716 by map-based cloning. We have constructed a high-resolution map of the I-3 region and have identified markers closely flanking I-3 as well as markers co-segregating with I-3. In addition, construction of a physical map based on these markers has been initiated. This review describes the context of our research and our progress towards isolating the I-3 gene. It also describes some important practical outcomes of our work, including the development and use of a PCR-based marker for marker-assisted selection for I-3, and the finding that the I-3 gene from LA716 is different to that from PI1414773, which we have now designated I-7. Tomato varieties combining I-3 and I-7 have been developed and are currently being introduced into commercial production to further safeguard tomato crops against Fusarium wilt.

RNA interference-inducing hairpin RNAs in plants act through the viral defence pathway

RNA interference (RNAi) is widely used to silence genes in plants and animals. it operates through the degradation of target mRNA by endonuclease complexes guided by approximately 21 nucleotide (nt) short interfering RNAs (siRNAs). A similar process regulates the expression of some developmental genes through approximately 21 nt microRNAs. Plants have four types of Dicer-like (DCL) enzyme, each producing small RNAs with different functions. Here, we show that DCL2, DCL3 and DCL4 in Arabidopsis process both replicating viral RNAs and RNAi-inducing hairpin RNAs (hpRNAs) into 22-, 24- and 21 nt siRNAs, respectively, and that loss of both DCL2 and DCL4 activities is required to negate RNAi and to release the plant's repression of viral replication. We also show that hpRNAs, similar to viral infection, can engender long-distance silencing signals and that hpRNA-induced silencing is suppressed by the expression of a virus-derived suppressor protein. These findings indicate that hpRNA-mediated RNAi in plants operates through the viral defence pathway.

Rheumatoid arthritis: links with cardiovascular disease and the receptor for advanced glycation end products

Cardiovascular (CV) disease is increased in patients with chronic inflammatory disease, including rheumatoid arthritis (RA). Furthermore it has become clear at a pathophysiological level, that atherosclerosis has striking similarities with autoimmune disease. This realization has come at a time of paradigm shift in how rheumatologists manage RA, with the availability of biological agents targeting key inflammatory cytokines. This review will focus on the possible causes of increased vascular disease in RA, including the role of traditional CV risk factors. Mechanisms potentially at play, such as C-reactive protein (CRP), altered coagulation, and cyclooxygenase (COX) -2 inhibitors will be covered in brief. The Receptor for Advanced Glycation End Products (RAGE) has been identified as a candidate molecule influencing response to ongoing inflammation and autoimmunity. There will be a focus on the role of RAGE in CV disease and RA. As has been the case with many novel molecules, functional polymorphisms are thought to alter disease expression and assist us in coming to terms with the biological activities of the parent molecule. The review will conclude with a discussion of the potential role of the RAGE Glycine 82 Serine polymorphism

Responding to interpersonal and physically provoking situations in classrooms: emotional intensity in children with attention deficit hyperactivity disorder

The present research investigated the emotional functioning of children with and without Attention Deficit Hyperactivity Disorder (ADHD), in order to examine the relationships between emotional intensity and classroom-based responses to physically and interpersonally provoking situations. Seventy children (35 with ADHD and 35 without ADHD) in Years 3–8 participated and were matched on age, gender, grade, and school class. Each child was observed individually in the classroom over two 20-min periods. The Responses to Interpersonal and Physically Provoking Situations Observation Schedule was used to record the frequency and severity of responses and the triggers for these during the observational periods. Children later rated their emotional intensity in response to hypothetical scenarios on the Emotional Intensity Scale for Children. Results revealed children with ADHD displayed significantly more frequent and severe challenging and solitary off-task behaviours, and significantly more frequent vocalisations and severe interactional off-task behaviours. For triggers, environmental and teacher-initiated distractions were significantly more frequently observed in children with ADHD. There were no differences in ratings of emotional intensity between children with and without ADHD, although a number of significant and meaningful correlations were observed between positive emotional intensity scores and responses and triggers.

Knowledge and understanding of choice diversity of residential care staff working with individuals with intellectual disabilities

The present study aimed to trial the effectiveness of 10 newly developed brief vignettes portraying typical interactions between staff and people with intellectual disabilities in residential care settings to assess the knowledge and understanding of staff about choice diversity, pre- and post-attendance at a staff training workshop. A total of 29 residential staff completed the Vignette Rating Scale and a knowledge questionnaire pre- and post-training. A t- test conducted on the vignettes revealed that respondents identified fewer choices in the post-test vignettes compared to the pre-test vignettes. Results showed no significant difference between the pre- and post-test data on the knowledge questionnaire. The questionnaire revealed a high level of knowledge about choice prior to and following training. The vignettes, however, proved effective in measuring changes in awareness of choice diversity among residential staff following participation in a staff training workshop.

Cue salience in multiple cue attentional capture

The predominant use of single element cues in visual attentional capture research motivated examination using dual capture cues. Participants in these studies viewed computer screens briefly displaying sequences of feature-defined positional cues and targets, with target identification response time recorded. Five initial experiments utilising the features of colour (purple) and intensity (bold font), and reported at EPC 2005, revealed contingent capture influences and suggested capture by colour cues may be more powerful than single cue literature has indicated. Three follow-up experiments manipulated displays and defining features to see if the conclusions remained. Experiments 6 and 7 investigated whether target identification in the initial series was based on a featural or singleton search. Experiment 8 then tested "onset' versus "purple" under the condition of specific attentional set, a featural change that appeared to remove purple colour dominance evidenced in the initial experimental series. Overall, outcomes of both experimental series suggest strong salience involvement with overtones of contingent capture for specific featural selections. The novel multi-cue approach revealed the significance of relative salience within these selections.