To be or not to be in the nucleolus

Compartmentalization has long been known to have a key role in regulation of cellular processes. By keeping enzymes and regulatory complexes in compartments where the delivery of substrate or exit of product is controlled, competing reactions can occur simultaneously in different parts of the cell. Moreover, spatial confinement facilitates the working of molecules participating in reaction chains and is crucial for coupling unfavourable with energetically favourable chemical reactions. Although in many cases intracellular compartmentalization relies on boundaries imposed by membranes, several non-membrane-bounded compartments exist in eukaryotic cells. One of these, the nucleolus, has recently attracted much attention. The emerging view is that molecular confinement in the nucleolus actively contributes to the control of cellular survival and proliferation.     

To be or not to be a hamlet pair in sympatry

Recent adaptive radiations, such as the fringillid finches on the Galapagos archipelago or the cichlid fishes in the East African Great Lakes, are invaluable model systems for evolutionary and ecological research. Puebla et al. , in this issue of Molecular Ecology , have established a group of colourful coral reef fishes from the Caribbean sea for studying the early phases of species formation in a marine adaptive radiation. It appears that local evolutionary processes are important in this system, which might have even triggered in situ speciation.     

To be or not to be toxic: aggregations in Huntington and Alzheimer disease

Insoluble aggregated proteins in Alzheimer disease and Huntington disease might not be pathogenic. Human studies have poor correlations between aggregates and clinical disease or pathology in these disorders, whereas mouse models have demonstrated that neuronal loss can occur in the absence of detectable aggregates. Furthermore, aggregates can exist in the absence of disease pathology in mice or symptoms in humans. Recent research suggests that soluble protein fragments, not insoluble aggregated proteins, are the toxic species in these disorders.     

Focus on histone variant H2AX: To be or not to be

Phosphorylation of histone variant H2AX at serine 139, named γH2AX, has been widely used as a sensitive marker for DNA double-strand breaks (DSBs). γH2AX is required for the accumulation of many DNA damage response (DDR) proteins at DSBs. Thus it is believed to be the principal signaling protein involved in DDR and to play an important role in DNA repair. However, only mild defects in DNA damage signaling and DNA repair were observed in H2AX-deficient cells and animals. Such findings prompted us and others to explore H2AX-independent mechanisms in DNA damage response. Here, we will review recent advances in our understanding of H2AX-dependent and independent DNA damage signaling and repair pathways in mammalian cells.     

To be or not to be a compatible solute: bioversatility of mannosylglycerate and glucosylglycerate

Mannosylglycerate (MG) is an intracellular organic solute found in some red algae, and several thermophilic bacteria and hyperthermophilic archaea. Glucosylglycerate (GG) was identified at the reducing end of a polysaccharide from mycobacteria and in a free form in a very few mesophilic bacteria and halophilic archaea. MG has a genuine role in the osmoadaptation and possibly in thermal protection of many hyper/thermophilic bacteria and archaea, but its role in red algae, where it was identified long before hyperthermophiles were even known to exist, remains to be clarified. The GG-containing polysaccharide was initially detected in Mycobacterium phlei and found to regulate fatty acid synthesis. More recently, GG has been found to be a major compatible solute under salt stress and nitrogen starvation in a few microorganisms. This review summarizes the occurrence and physiology of MG accumulation, as well as the distribution of GG, as a free solute or associated with larger macromolecules. We also focus on the recently identified pathways for the synthesis of both molecules, which were elucidated by studying hyper/thermophilic MG-accumulating organisms. The blooming era of genomics has now allowed the detection of these genes in fungi and mosses, opening a research avenue that spans the three domains of life, into the role of these two sugar derivatives.     

To be or not to be a responder in T-cell responses: ubiquitous oligopeptides in all proteins

Amino acid sequences of all proteins are essays written in the same language. Accordingly, the same set of words and phrases (oligopeptides) appear in totally unrelated proteins. The reason that only certain individuals of particular major histocompatibility complex (MHC) haplotypes can mount T-cell responses against a given antigen of pathogens is found in the fact that T-cell receptors are designed to recognize 18–20 residue-long peptide fragments sandwiched between two -helices of class I or class II MHC molecules. At this range of peptide lengths, most would appear as self, while nonselfness of the remainders are destined to be quite ambiguous, hence creating responders and nonresponders.     

To be or not to be [fertile], that is the question

Background

According to our literature analysis, there are no data focused on spermatozoa emotional representations in childless men and data on the emotional repercussions of a diagnosis of infertility on men are still scarce. Thus, in this work, we investigated what the presence or absence of spermatozoa in the semen symbolize for men.

Material and methods

To answer this question, 441 childless heterosexual men participated in an anonymous, prospective, Internet-based survey.

Results

In response to the question “What would having a high or normal sperm count symbolize for you?” the most frequent answer was “ability to father a child”. Men living with a partner were significantly more likely than single men to answer “ability to father a child” (p?<?0.05) and less likely to answer “virility” and/or “ability to have an erection/ejaculation” (p?=?0.001). In response to the question “If you found out that you had a low sperm count or no spermatozoa at all, how would you feel?”, most of the men stated that they would be disappointed. Men living with a partner were more likely to state that they would feel ashamed (p?<?0.05) or guilty with regard to their partner (p?<?0.0001).

Conclusions

These preliminary results should help us to improve (i) the way that male infertility is announced (it is easier to find the right words if one understands the possible importance of having a high sperm count) and (ii) the psychological, marital and sexual counselling provided to men with a diagnosis of infertility.

     

To die or not to die: Shigella has an answer

Invasion of epithelial cells by Shigella is a critical step in the pathogenesis of bacillary dysentery. In this issue of Cell Host & Microbe, Bergounioux et?al. (2012) uncover a complex interplay of proinvasion, prosurvival, and prodeath signals centered on the activation of calpain protease by the Shigella VirA protein.     

To be or not to be what you eat: regulation of stoichiometric homeostasis among autotrophs and heterotrophs

Homeostasis of element composition is one of the central concepts of ecological stoichiometry. In this context, homeostasis is the resistance to change of consumer body composition in response to the chemical composition of consumer's food. To simplify theoretical analysis, it has generally been assumed that autotrophs exhibit flexibility in their composition, while heterotrophs are confined to a constant (strictly homeostatic) body composition. Yet, recent studies suggest that heterotrophs are not universally strictly homeostatic. We examined the degree to which autotrophs and heterotrophs regulate stoichiometric homeostasis (P:C, N:C, N:P, or %P and %N). We conducted a quantitative review and meta‐analysis using 132 datasets extracted from 57 literature sources which examined the dependence of organismal stoichiometry on resource stoichiometry. Among individual datasets, there was a wide range of responses from strictly homeostatic to non‐homeostatic. Even within heterotrophic organisms, varying levels of homeostasis were observed. Comparing the degree of homeostasis between organisms based on large‐scale habitat types using meta‐analysis indicated some significant differences between groups. For example, aquatic macroinvertebrates were significantly more homeostatic in terms of P:C than terrestrial invertebrates. Our meta‐analysis also confirmed that, with regard to N:P, heterotrophs are significantly more homeostatic than autotrophs. Furthermore, our analysis indicated that the homeostasis parameter 1/H, despite being a potentially useful predictive metric, has to be utilized with caution since it oversimplifies some important aspects of the responses of organisms to elemental imbalances. This critical evaluation of stoichiometric homeostasis contributes to a better understanding of many food‐web interactions, which are commonly driven by elemental imbalances between consumers and their resources.