Effect of ethanol and isopropanol on the activity of alcohol dehydrogenase,viability and life-span inDrosophila melanogaster andDrosophila funebris

Summary The effects caused by the addition of 2 alcohols to the culture medium of 2 species ofDrosophila, D. melanogaster andD. funebris, are compared. Ethanol at 1% concentration causes slight and tolerable changes in both species. 1% isopropanol is lethal in 1 species and causes drastic changes in the other.The author acknowledge Dr A. Prevost for continuous support and E. Juan and Ll. Serra for their helpful suggestions.     

Polymorphisms in FKBP5 are associated with increased recurrence of depressive episodes and rapid response to antidepressant treatment

The stress hormone-regulating hypothalamic-pituitary-adrenal (HPA) axis has been implicated in the causality as well as the treatment of depression. To investigate a possible association between genes regulating the HPA axis and response to antidepressants and susceptibility for depression, we genotyped single-nucleotide polymorphisms in eight of these genes in depressed individuals and matched controls. We found significant associations of response to antidepressants and the recurrence of depressive episodes with single-nucleotide polymorphisms in FKBP5, a glucocorticoid receptor-regulating cochaperone of hsp-90, in two independent samples. These single-nucleotide polymorphisms were also associated with increased intracellular FKBP5 protein expression, which triggers adaptive changes in glucocorticoid receptor and, thereby, HPA-axis regulation. Individuals carrying the associated genotypes had less HPA-axis hyperactivity during the depressive episode. We propose that the FKBP5 variant-dependent alterations in HPA-axis regulation could be related to the faster response to antidepressant drug treatment and the increased recurrence of depressive episodes observed in this subgroup of depressed individuals. These findings support a central role of genes regulating the HPA axis in the causality of depression and the mechanism of action of antidepressant drugs.     

Heterozygous TGFBR2 mutations in Marfan syndrome

Marfan syndrome is an extracellular matrix disorder with cardinal manifestations in the eye, skeleton and cardiovascular systems associated with defects in the gene encoding fibrillin (FBN1) at 15q21.1 (ref. 1). A second type of the disorder (Marfan syndrome type 2; OMIM 154705) is associated with a second locus, MFS2, at 3p25-p24.2 in a large French family (family MS1). Identification of a 3p24.1 chromosomal breakpoint disrupting the gene encoding TGF-beta receptor 2 (TGFBR2) in a Japanese individual with Marfan syndrome led us to consider TGFBR2 as the gene underlying association with Marfan syndrome at the MSF2 locus. The mutation 1524G-->A in TGFBR2 (causing the synonymous amino acid substitution Q508Q) resulted in abnormal splicing and segregated with MFS2 in family MS1. We identified three other missense mutations in four unrelated probands, which led to loss of function of TGF-beta signaling activity on extracellular matrix formation. These results show that heterozygous mutations in TGFBR2, a putative tumor-suppressor gene implicated in several malignancies, are also associated with inherited connective-tissue disorders.     

Susceptibility to leprosy is associated with PARK2 and PACRG

Leprosy is caused by Mycobacterium leprae and affects about 700,000 individuals each year. It has long been thought that leprosy has a strong genetic component, and recently we mapped a leprosy susceptibility locus to chromosome 6 region q25-q26 (ref. 3). Here we investigate this region further by using a systematic association scan of the chromosomal interval most likely to harbour this leprosy susceptibility locus. In 197 Vietnamese families we found a significant association between leprosy and 17 markers located in a block of approx. 80 kilobases overlapping the 5' regulatory region shared by the Parkinson's disease gene PARK2 and the co-regulated gene PACRG. Possession of as few as two of the 17 risk alleles was highly predictive of leprosy. This was confirmed in a sample of 975 unrelated leprosy cases and controls from Brazil in whom the same alleles were strongly associated with leprosy. Variants in the regulatory region shared by PARK2 and PACRG therefore act as common risk factors for leprosy.     

Peripheral B cell survival

Recent findings suggest that lymphocyte survival is a continuous active process and support the role of B cell receptor engagement in B cell survival. In this context the conflict of survival interests between the diverse B cells gives rise to a pattern of interactions which mimics the behavior of complex ecological systems. In response to competition lymphocytes modify their survival requirements and diverge to occupy different immunological niches through differentiation. Thus naive and memory-activated B cell populations show independent homeostatic regulation. We discuss how niche differentiation allows the coexistence of different cell types and guarantees both repertoire diversity and efficient immune responses.     

Functional interaction of phytochrome B and cryptochrome 2

Light is a crucial environmental signal that controls many photomorphogenic and circadian responses in plants. Perception and transduction of light is achieved by at least two principal groups of photoreceptors, phytochromes and cryptochromes. Phytochromes are red/far-red light-absorbing receptors encoded by a gene family of five members (phyA to phyE) in Arabidopsis. Cryptochrome 1 (cry1), cryptochrome 2 (cry2) and phototropin are the blue/ultraviolet-A light receptors that have been characterized in Arabidopsis. Previous studies showed that modulation of many physiological responses in plants is achieved by genetic interactions between different photoreceptors; however, little is known about the nature of these interactions and their roles in the signal transduction pathway. Here we show the genetic interaction that occurs between the Arabidopsis photoreceptors phyB and cry2 in the control of flowering time, hypocotyl elongation and circadian period by the clock. PhyB interacts directly with cry2 as observed in co-immunoprecipitation experiments with transgenic Arabidopsis plants overexpressing cry2. Using fluorescent resonance energy transfer microscopy, we show that phyB and cry2 interact in nuclear speckles that are formed in a light-dependent fashion.     

Little or no solar wind enters Venus' atmosphere at solar minimum

Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum.     

Quantifying social group evolution

The rich set of interactions between individuals in society results in complex community structure, capturing highly connected circles of friends, families or professional cliques in a social network. Thanks to frequent changes in the activity and communication patterns of individuals, the associated social and communication network is subject to constant evolution. Our knowledge of the mechanisms governing the underlying community dynamics is limited, but is essential for a deeper understanding of the development and self-optimization of society as a whole. We have developed an algorithm based on clique percolation that allows us to investigate the time dependence of overlapping communities on a large scale, and thus uncover basic relationships characterizing community evolution. Our focus is on networks capturing the collaboration between scientists and the calls between mobile phone users. We find that large groups persist for longer if they are capable of dynamically altering their membership, suggesting that an ability to change the group composition results in better adaptability. The behaviour of small groups displays the opposite tendency-the condition for stability is that their composition remains unchanged. We also show that knowledge of the time commitment of members to a given community can be used for estimating the community's lifetime. These findings offer insight into the fundamental differences between the dynamics of small groups and large institutions.