Heritability: one word, three concepts

The term 'heritability', which evokes the image of transmission from parents to children, is used in biology to characterize the resemblance of related individuals in terms of a given characteristic, and to analyse the genetic and environmental causes of this resemblance. In fact, there are three definitions of heritability and it is important to distinguish among these carefully in order to avoid misinterpretations. Various techniques for measuring associated parameters are linked to these definitions. A rigorous analysis of the assumptions which permit the interpretation of parameter estimates is necessary to avoid false conclusions.     

Plant development: three steps for stomata

Three basic helix-loop-helix proteins regulate sequential steps in the formation of stomata: SPEECHLESS initiates entry into the stomatal lineage; MUTE controls asymmetric divisions of stomatal precursor cells; and FAMA promotes guard cell differentiation.     

Membrane trafficking: three steps to fusion

Membrane fusion involves the action of members of the SNARE protein family as well as Sec1/Munc18 (SM) proteins, which have been found to interact with SNAREs in three distinct ways. Recent work has established that Munc18-1 directly stimulates fusion and possibly uses all three modes of SNARE interaction.     

BRCT domains: Easy as one,two, three

BRCA1 C-terminal (BRCT) domains are integral signaling modules in the DNA damage response (DDR). Aside from their established roles as phospho-peptide binding modules, BRCT domains have been implicated in phosphorylation-independent protein interactions, DNA binding and poly(ADP-ribose) (PAR) binding. These numerous functions can be attributed to the diversity in BRCT domain structure and architecture, where domains can exist as isolated single domains or assemble into higher order homo- or hetero-domain complexes. In this review, we incorporate recent structural and biochemical studies to demonstrate how structural features allow single and tandem BRCT domains to attain a high degree of functional diversity.Key words: BRCT domain, DNA repair, phosphorylation, phospho-peptide interaction, protein interaction, DNA binding, DNA damage response     

Amazonian paleoecological histories: one hill, three watersheds

Data from the Hill of Six Lakes, in the northwestern Brazilian Amazon region, provide three records of paleoclimatic and vegetation change in lowland Amazonia that span the last 170,000 years. Three lakes, Verde, Pata and Dragão, which occupy separate watersheds on the hill, provide the most detailed image yet obtained of ice-age conditions in lowland Amazonia. Well-dated sedimentary records for fossil palynological, charcoal, cation, and pigment, data are presented.The data indicate the continuous presence of mesic forest throughout the last ice age. Oscillations of lake level are recorded and the lowstands are attributed to reduced precipitation inputs to systems delicately balanced between water loss (leakage through the floor of the basin) and gain (precipitation). Gross stratigraphy, algal remains, and paleochemistry suggest that the stands of high and low lake level were cyclic, apparently correlating precessional orbital variation. Times of lake lowstand coincide with wet season (December-January-February, DJF) insolation minima. The strongest of eight lowstand cycles occurred ca. 35,000 to 27,000 cal BP.Even during lowstand episodes, pollen is well preserved and provides a clear signal of uninterrupted forest cover. The principal lowland elements are continuously present in the record, suggesting the long-term (Quaternary) availability of the lowland forest biome in this region. However, during the late Pleistocene the forest changed in composition with the expansion or invasion of montane floral elements creating communities of the mesic forest biome without modern analogs. While precipitation cycles were causing lake levels to rise and fall, the principal influence on vegetation appears to have been cooling. In the late Pleistocene, the population expansion of montane elements at lower elevations is consistent with a cooling of 4-5 °C.     

Guidance for product category rule development: process,outcome, and next steps

Purpose

The development of product category rules (PCRs) is inconsistent among the program operators using ISO 14025 as the basis. Furthermore, the existence of several other product claim standards and specifications that require analogous rules for making product claims has the potential to reduce any consistency in PCRs present in the ISO 14025 domain and result in unnecessary duplication of PCRs. These inconsistencies and duplications can be attributed to (a) insufficient specificity in related standards, (b) the presence of several standards and specifications, (c) lack of/limited coordination among program operators, and (d) lack of a single global database for PCRs. As a result, current PCR development threatens the legitimacy of life cycle assessment-based product claims.

Process

Through discussions over the past few years, in multistakeholder organizations, it has become clear that more guidance on the development of PCRs is necessary. In response to this need, the Product Category Rule Guidance Development Initiative (www.pcrguidance.org) was launched as an independent multistakeholder effort in early 2012. The premise for the Initiative was that the Guidance would be created by a voluntary group of international stakeholders that would share ownership of the outputs.

Outcome

The Guidance is now published, along with supplementary materials, on the Initiative website. The guidance document specifies requirements, recommendations, and options on (1) steps to be taken before PCR creation; (2) elements of a PCR; (3) review, publication, and use of PCRs; and (4) best practices for PCR development and management. Supplementary materials include a PCR template, a conformity assessment form, and a list of program operators from around the world.

Conclusions

The Guidance will help reduce cost and time to develop a PCR by supporting the adaptation of an existing PCR or by building on elements from existing PCRs. It will help reduce confusion and frustration when creating PCRs that are based on one or more standards and programs. Overall, the Guidance is a robust handbook for consistency and clarity in the development of PCRs.     

Three down and counting: the transformation of human mammary cells from normal to malignant in three steps

An array of genetic mutations associated with human breast cancers has been identified. However, which specific combination of mutations permit normal cells to form breast cancer remains unknown. Elenbaas et al. recently described an experimental system for studying the genetic requirements for the development of breast cancer.     

Two steps forward, one step back: the pleiotropic effects of favoured alleles

Pleiotropy is one of the most commonly observed attributes of genes. Yet the extent and influence of pleiotropy have been underexplored in population genetics models. In this paper, I quantify the extent to which pleiotropy inhibits the spread of alleles in response to directional selection on a focal trait. Under the assumption that pleiotropic effects are extensive and deleterious, the fraction of alleles that are beneficial overall is severely limited by pleiotropy and rises nearly linearly with the strength of directional selection on the focal trait. Over a broad class of distribution of pleiotropic effects, the mean selective effect of those alleles that are beneficial overall is halved, on average, by pleiotropy. The fraction of new mutant alleles that are beneficial overall and that succeed in fixing within a population is even more severely limited when directional selection is weak, but it rises quadratically with the strength of directional selection. Finally, the mean selective effect of mutant alleles that are beneficial and succeed in fixing is reduced by one-third, on average, by pleiotropy. These results help to shape our understanding of the evolutionary inertia caused by pleiotropy.     

Raf phosphorylation: one step forward and two steps back

We understand Raf-1 activation relatively well but know less about how it is inactivated. An exciting study in this issue of Molecular Cell now describes the molecular basis underlying the transient nature of Raf-1 signaling.     

Three steps to the immortality of cancer cells: senescence,polyploidy and self-renewal

Background

Hepatocellular carcinoma (HCC) exhibits strong intrinsic and acquired drug resistance which is the main obstacle to chemotherapy. Overexpression of ATP binding cassette (ABC) proteins correlates with activation of mitogen activated protein kinase (MAPK) pathway in HCC. Here, we systematically investigated the inhibition of MAPK pathway and its role in regulating HCC cell growth as well as ABC proteins MRP1 and MRP3 expression.

Methods

The Raf1 kinase inhibitor (GW5074) and different MEK inhibitors (U0126 and AZD6244) were used to treat HCC cells to identify their effects on HCC cell growth and ABC proteins expression in vitro. Cell viability tests were performed after the treatment of MAPK pathway inhibitors and in combination with gemcitabine or doxorubicin. Western blot was applied to assess the changes of MAPK pathway and protein expression of MRP1 and MRP3. Flow cytometry was used to measure intracellular doxorubicin accumulation after the treatment of MEK inhibitors.

Results

Both Raf1 inhibitor (GW5074) and MEK inhibitors (U0126 and AZD6244) suppressed HCC cell growth in a dose dependent manner. Pre-treatment of MEK inhibitor U0126 or AZD6244 sensitized HCC cells to gemcitabine or doxorubicin based chemotherapy. Raf1 inhibitor GW5074 had no effect on MRP1 and MRP3 protein expression. Treatment of gemcitabine or doxorubicin activated phosphorylated ERK and induced the upregulation of MRP1 and MRP3. MEK inhibitors U0126 and AZD6244 deactivated phosphorylated ERK, decreased endogenous MRP1 expression, reversed gemcitabine or doxorubicin induced MRP1 and MRP3 upregulation, and increased the intracellular doxorubicin accumulation.

Conclusion

This study provides evidence that MEK inhibitors sensitize HCC cells to chemotherapy by increasing intracellular chemodrug accumulation. MEK inhibirors U0126 and AZD6244 reduced MRP1 as well as MRP3 expression, and may contribute partially to the sensitization. The combination of MEK inhibitor and conventional chemotherapy may offer new therapeutic option for the treatment of resistant HCC.     

Plasma fibronectin: three steps to purification and stability.

Large amounts of soluble fibronectin were easily purified from cryoprecipitated or fresh citrated human blood plasma by a three-step combination of gelatin and heparin-cellufine affinity chromatography. The elution conditions were optimized to obtain a homogeneous fraction on SDS-PAGE and Western blot under reducing condition. No proteolytic activities were detected by zymography at acidic or neutral pH. Furthermore, the fibronectin preparation was stable over time up to 456 h at 37 degrees C in the presence of calcium, zinc, or mercury. This preparation of very stable fibronectin, called highly purified fibronectin (hpFN), gave a yield of 7.00 +/- 0.77 mg of fibronectin per gram of cryoprecipitated plasma and 0.16 mg of fibronectin per milliliter of fresh citrated, giving a yield of 32 to 53% (from presumed fibronectin concentration). This preparation may be useful for cellular tests and interaction analysis.     

Three,two, one yeast fatty acid desaturases: regulation and function

Fatty acid composition of biological membranes functionally adapts to environmental conditions by changing its composition through the activity of lipid biosynthetic enzymes, including the fatty acid desaturases. Three major desaturases are present in yeasts, responsible for the generation of double bonds in position C9–C10, C12–C13 and C15–C16 of the carbon backbone. In this review, we will report data addressed to define the functional role of basidiomycete and ascomycete yeast desaturase enzymes in response to various external signals and the regulation of the expression of their corresponding genes. Many yeast species have the complete set of three desaturases; however, only the Δ9 desaturase seems to be necessary and sufficient to ensure yeast viability. The evolutionary issue of this observation will be discussed.     

Reform of mental health care in Serbia: ten steps plus one

Disastrous events in the country and the region caused a 13.5% increase in the prevalence of mental and behavioral disorders in Serbia in the last few years, thus making them the second largest public health problem. Due to prolonged adversities, the health system has deteriorated and is facing specific challenges. However, the reform of mental health care has been initiated, with a lot of positive movements such as the preparation of a national policy for mental health care and a law for protection of mentally ill individuals. The transformation of mental health services has started, with an accent on community care, antistigma campaigns and continuing education. Based on an assessment carried out by the National Committee on Mental Health, service provision, number of professionals working in services, funding arrangements, pathways into care, user/carer involvement and other specific issues are reported.