Cul4A is essential for spermatogenesis and male fertility

The mammalian Cul4 genes, Cul4A and Cul4B, encode the scaffold components of the cullin-based E3 ubiquitin ligases. The two Cul4 genes are functionally redundant. Recent study indicated that mice expressing a truncated CUL4A that fails to interact with its functional partner ROC1 exhibit no developmental phenotype. We generated a Cul4A−/− strain lacking exons 4–8 that does not express any detectable truncated protein. In this strain, the male mice are infertile and exhibit severe deficiencies in spermatogenesis. The primary spermatocytes are deficient in progression through late prophase I, a time point when expression of the X-linked Cul4B gene is silenced due to meiotic sex chromosome inactivation. Testes of the Cul4A−/− mice exhibit extensive apoptosis. Interestingly, the pachytene spermatocytes exhibit persistent double stranded breaks, suggesting a deficiency in homologous recombination. Also, we find that CUL4A localizes to the double stranded breaks generated in pre-pachytene spermatocytes. The observations identify a novel function of CUL4A in meiotic recombination and demonstrate an essential role of CUL4A in spermatogenesis.     

The representation of heart development in the gene ontology

An understanding of heart development is critical in any systems biology approach to cardiovascular disease. The interpretation of data generated from high-throughput technologies (such as microarray and proteomics) is also essential to this approach. However, characterizing the role of genes in the processes underlying heart development and cardiovascular disease involves the non-trivial task of data analysis and integration of previous knowledge. The Gene Ontology (GO) Consortium provides structured controlled biological vocabularies that are used to summarize previous functional knowledge for gene products across all species. One aspect of GO describes biological processes, such as development and signaling.In order to support high-throughput cardiovascular research, we have initiated an effort to fully describe heart development in GO; expanding the number of GO terms describing heart development from 12 to over 280. This new ontology describes heart morphogenesis, the differentiation of specific cardiac cell types, and the involvement of signaling pathways in heart development. This work also aligns GO with the current views of the heart development research community and its representation in the literature. This extension of GO allows gene product annotators to comprehensively capture the genetic program leading to the developmental progression of the heart. This will enable users to integrate heart development data across species, resulting in the comprehensive retrieval of information about this subject.The revised GO structure, combined with gene product annotations, should improve the interpretation of data from high-throughput methods in a variety of cardiovascular research areas, including heart development, congenital cardiac disease, and cardiac stem cell research. Additionally, we invite the heart development community to contribute to the expansion of this important dataset for the benefit of future research in this area.     

Mutational analysis of the hypervariable region of hepatitis e virus reveals its involvement in the efficiency of viral RNA replication

The RNA genome of the hepatitis E virus (HEV) contains a hypervariable region (HVR) in ORF1 that tolerates small deletions with respect to infectivity. To further investigate the role of the HVR in HEV replication, we constructed a panel of mutants with overlapping deletions in the N-terminal, central, and C-terminal regions of the HVR by using a genotype 1 human HEV luciferase replicon and analyzed the effects of deletions on viral RNA replication in Huh7 cells. We found that the replication levels of the HVR deletion mutants were markedly reduced in Huh7 cells, suggesting a role of the HVR in viral replication efficiency. To further verify the results, we constructed HVR deletion mutants by using a genetically divergent, nonmammalian avian HEV, and similar effects on viral replication efficiency were observed when the avian HEV mutants were tested in LMH cells. Furthermore, the impact of complete HVR deletion on virus infectivity was tested in chickens, using an avian HEV mutant with a complete HVR deletion. Although the deletion mutant was still replication competent in LMH cells, the complete HVR deletion resulted in a loss of avian HEV infectivity in chickens. Since the HVR exhibits extensive variations in sequence and length among different HEV genotypes, we further examined the interchangeability of HVRs and demonstrated that HVR sequences are functionally exchangeable between HEV genotypes with regard to viral replication and infectivity in vitro, although genotype-specific HVR differences in replication efficiency were observed. The results showed that although the HVR tolerates small deletions with regard to infectivity, it may interact with viral and host factors to modulate the efficiency of HEV replication.     

Biochemical studies on the production of neuraminidase by environmental isolates of Vibrio cholerae non-O1 from Bulgaria

Neuraminidase is a key factor in the infectious process of many viruses and pathogenic bacteria. The neuraminidase enzyme secreted by the etiological agent of cholera?- Vibrio cholerae О1?- is well studied in contrast with the one produced by non-O1/non-O139 V.?cholerae. Environmental non-O1/non-O139 V. cholerae isolates from Bulgaria were screened for production of neuraminidase. The presence of the neuraminidase gene nanH was detected in 18.5% of the strains. Тhe strain showing highest activity (30 U/mL),?V. cholerae non-O1/13, was used to investigate the enzyme production in several media and at different aeration conditions. The highest production of extracellular neuraminidase was observed under microaerophilic conditions, which is possibly related to its role in the infection of intestine epithelium, where the oxygen content is low. On the other hand, this is another advantage of the microbe in such microaerophilic environments as sediments and lake mud. The highest production of intracellular neuraminidase was observed at anaerobic conditions. The ratio of extracellular to intracellular neuraminidase production in V. cholerae was investigated. The temperature optimum of the enzyme was determined to be 50?°C and the pH optimum to be?5.6-5.8.     

The effects of polymer phase ratio and feeding strategy on solid–liquid TPPBs for the production of <Emphasis Type="SmallCaps">l</Emphasis>-phenylacetylcarbinol from benzaldehyde using <Emphasis Type="Italic">Candida utilis</Emphasis>

Purpose of Work  

To increase the bioproduction of l-phenylacetylcarbinol (PAC), a precursor molecule in the synthesis of the decongestants ephedrine and pseudoephedrine and which suffers from substrate, product, and by-product inhibition, by ensuring that the delivery of the substrate, benzaldehyde, is maintained within a strict concentration window.     

Irrational decision-making in an amoeboid organism: transitivity and context-dependent preferences

Most models of animal foraging and consumer choice assume that individuals make choices based on the absolute value of items and are therefore ‘economically rational’. However, frequent violations of rationality by animals, including humans, suggest that animals use comparative valuation rules. Are comparative valuation strategies a consequence of the way brains process information, or are they an intrinsic feature of biological decision-making? Here, we examine the principles of rationality in an organism with radically different information-processing mechanisms: the brainless, unicellular, slime mould Physarum polycephalum. We offered P. polycephalum amoebas a choice between food options that varied in food quality and light exposure (P. polycephalum is photophobic). The use of an absolute valuation rule will lead to two properties: transitivity and independence of irrelevant alternatives (IIA). Transitivity is satisfied if preferences have a consistent, linear ordering, while IIA states that a decision maker''s preference for an item should not change if the choice set is expanded. A violation of either of these principles suggests the use of comparative rather than absolute valuation rules. Physarum polycephalum satisfied transitivity by having linear preference rankings. However, P. polycephalum''s preference for a focal alternative increased when a third, inferior quality option was added to the choice set, thus violating IIA and suggesting the use of a comparative valuation process. The discovery of comparative valuation rules in a unicellular organism suggests that comparative valuation rules are ubiquitous, if not universal, among biological decision makers.     

Triheptanoin partially restores levels of tricarboxylic acid cycle intermediates in the mouse pilocarpine model of epilepsy

Triheptanoin, the triglyceride of heptanoate, is anticonvulsant in various epilepsy models. It is thought to improve energy metabolism in the epileptic brain by re‐filling the tricarboxylic acid (TCA) cycle with C4‐intermediates (anaplerosis). Here, we injected mice with [1,2‐¹³C]glucose 3.5–4 weeks after pilocarpine‐induced status epilepticus (SE) fed either a control or triheptanoin diet. Amounts of metabolites and incorporations of ¹³C were determined in extracts of cerebral cortices and hippocampal formation and enzyme activity and mRNA expression were quantified. The percentage enrichment with two ¹³C atoms in malate, citrate, succinate, and GABA was reduced in hippocampal formation of control‐fed SE compared with control mice. Except for succinate, these reductions were not found in triheptanoin‐fed SE mice, indicating that triheptanoin prevented a decrease of TCA cycle capacity. Compared to those on control diet, triheptanoin‐fed SE mice showed few changes in most other metabolite levels and their ¹³C labeling. Reduced pyruvate carboxylase mRNA and enzyme activity in forebrains and decreased [2,3‐¹³C]aspartate amounts in cortex suggest a pyruvate carboxylation independent source of C‐4 TCA cycle intermediates. Most likely anaplerosis was kept unchanged by carboxylation of propionyl‐CoA derived from heptanoate. Further studies are proposed to fully understand triheptanoin's effects on neuroglial metabolism and interaction.

     

Chemosensory and thermal cue responses in the sub-Antarctic moth Pringleophaga marioni: Do caterpillars choose Wandering Albatross nest proxies?

On the South Indian Ocean Province Islands of the sub-Antarctic, most nutrients are processed through a detritus-based food web. On Marion Island, larvae of the moth Pringleophaga marioni are one of the key decomposers. Abundance of these caterpillars is higher in newly abandoned Wandering Albatross (Diomedea exulans) nests than other habitats, and this observation has been explained by hypotheses regarding the thermal and nutrient advantages of nests. These hypotheses require a mechanism for increasing the abundance of caterpillars, since nests are an ephemeral resource, and here, we determine whether caterpillars respond to chemosensory and thermal cues using a laboratory choice chamber approach. Caterpillars show no significant preference for newly abandoned nest material over no other choice, old nest material, and the common mire moss Sanionia uncinata. Caterpillars that are acclimated to warm (15 °C) conditions do prefer lower (5 °C) to higher (15 °C) temperatures, perhaps reflecting negative effects of prolonged exposure to warm temperatures on growth. Caterpillars also show significant avoidance of conspecifics, possibly because of incidental cannibalism previously reported in this species. Thus, we find no empirical support for nest-finding ability in caterpillars based on chemosensory or thermal cues. It is possible that adult females or very early instar caterpillars show such ability, or high caterpillar density and biomass in nests are an incidental consequence of better conditions in the nests or deposition by the birds during nest construction.