RNA-based gene duplication sheds new light on mammalian sex chromosome evolution

ABSTRACT : Gene duplication is a fundamental source of raw material for the origin of genetic novelty. It has been assumed for a long time that DNA-based gene duplication was the only source of new genes. Recently however, RNA-based gene duplication (retroposition) was shown in multiple organisms to contribute significantly to their genetic diversity. This mechanism produces intronless gene copies (retrocopies) that are inserted in random genomic position, independent of the position of the parental source genes. In human, mouse and fruit fly, it was demonstrated that the X-linked genes spawned an excess of functional retroposed gene copies (retrogenes). In human and mouse, the X chromosome also recruited an excess of retrogenes. Here we further characterized these interesting biases related to the X chromosome in mammals. Firstly, we have confirmed presence of the aforementioned biases in dog and opossum genome. Then based on the expression profile of retrogenes during various spermatogenetic stages, we have provided solid evidence that meiotic sex chromosome inactivation (MSCI) is responsible for an excess of retrogenes stemming from the X chromosome. Moreover, we showed that the X-linked genes started to export an excess of retrogenes just after the split of eutherian and marsupial mammalian lineages. This suggests that MSCI has originated around this time as well. More fundamentally, as MSCI reflects the spread of recombination barrier between the X and Y chromosomes during their evolution, our observation allowed us to re-estimate the age of mammalian sex chromosomes. Previous estimates suggested that they emerged in the common ancestor of all mammals (before the split of monotreme lineage); whereas, here we showed that they originated around the split of marsupial and eutherian lineages, after the divergence of monotremes. Thus, the therian (marsupial and eutherian) sex chromosomes are younger than previously thought. Thereafter, we have characterized the bias related to the recruitment of genes to the X chromosome. Sexually antagonistic forces are most likely driving this pattern. Using our limited retrogenes expression data, it is difficult to determine the exact nature of these forces but some conclusions have been made. Lastly, we looked at the history of this biased recruitment: it commenced around the split of marsupial and eutherian lineages (akin to the biased export of genes out of the X). In fact, the sexually antagonistic forces are predicted to appear just around that time as well. Thereby, the history of the recruitment of genes to the X, provides an indirect evidence that these forces are responsible for this bias.

FHY1 mediates nuclear import of the light-activated phytochrome A photoreceptor.

The phytochrome (phy) family of photoreceptors is of crucial importance throughout the life cycle of higher plants. Light-induced nuclear import is required for most phytochrome responses. Nuclear accumulation of phyA is dependent on two related proteins called FHY1 (Far-red elongated HYpocotyl 1) and FHL (FHY1 Like), with FHY1 playing the predominant function. The transcription of FHY1 and FHL are controlled by FHY3 (Far-red elongated HYpocotyl 3) and FAR1 (FAr-red impaired Response 1), a related pair of transcription factors, which thus indirectly control phyA nuclear accumulation. FHY1 and FHL preferentially interact with the light-activated form of phyA, but the mechanism by which they enable photoreceptor accumulation in the nucleus remains unsolved. Sequence comparison of numerous FHY1-related proteins indicates that only the NLS located at the N-terminus and the phyA-interaction domain located at the C-terminus are conserved. We demonstrate that these two parts of FHY1 are sufficient for FHY1 function. phyA nuclear accumulation is inhibited in the presence of high levels of FHY1 variants unable to enter the nucleus. Furthermore, nuclear accumulation of phyA becomes light- and FHY1-independent when an NLS sequence is fused to phyA, strongly suggesting that FHY1 mediates nuclear import of light-activated phyA. In accordance with this idea, FHY1 and FHY3 become functionally dispensable in seedlings expressing a constitutively nuclear version of phyA. Our data suggest that the mechanism uncovered in Arabidopsis is conserved in higher plants. Moreover, this mechanism allows us to propose a model explaining why phyA needs a specific nuclear import pathway.

Chromatic pupil responses: preferential activation of the melanopsin-mediated versus outer photoreceptor-mediated pupil light reflex.

OBJECTIVE: To weight the rod-, cone-, and melanopsin-mediated activation of the retinal ganglion cells, which drive the pupil light reflex by varying the light stimulus wavelength, intensity, and duration. DESIGN: Experimental study. PARTICIPANTS: Forty-three subjects with normal eyes and 3 patients with neuroretinal visual loss. METHODS: A novel stimulus paradigm was developed using either a long wavelength (red) or short wavelength (blue) light given as a continuous Ganzfeld stimulus with stepwise increases over a 2 log-unit range. The pupillary movement before, during, and after the light stimulus was recorded in real time with an infrared illuminated video camera. MAIN OUTCOME MEASURES: The percent pupil contraction of the transient and sustained pupil response to a low- (1 cd/m(2)), medium- (10 cd/m(2)), and high-intensity (100 cd/m(2)) red- and blue-light stimulus was calculated for 1 eye of each subject. From the 43 normal eyes, median and 25th, 75th, 5th, and 95th percentile values were obtained for each stimulus condition. RESULTS: In normal eyes at lower intensities, blue light evoked much greater pupil responses compared with red light when matched for photopic luminance. The transient pupil contraction was generally greater than the sustained contraction, and this disparity was greatest at the lowest light intensity and least apparent with bright (100 cd/m(2)) blue light. A patient with primarily rod dysfunction (nonrecordable scotopic electroretinogram) showed significantly reduced pupil responses to blue light at lower intensities. A patient with achromatopsia and an almost normal visual field showed selective reduction of the pupil response to red-light stimulation. A patient with ganglion cell dysfunction owing to anterior ischemic optic neuropathy demonstrated global loss of pupil responses to red and blue light in the affected eye. CONCLUSIONS: Pupil responses that differ as a function of light intensity and wavelength support the hypothesis that selected stimulus conditions can produce pupil responses that reflect phototransduction primarily mediated by rods, cones, or melanopsin. Use of chromatic pupil responses may be a novel way to diagnose and monitor diseases affecting either the outer or inner retina.

An ocellar "pupil" that does not change with light intensity, but with the insect age in Triatoma infestans

The simple eyes (ocelli) of recently emerged adult Triatoma infestans exhibit a narrow elongated "pupil", surrounded by a ring of brown-reddish pigment, the "iris". This pupil does not respond to changes in the illumination, but varies in size after the imaginal ecdysis. This change corresponds, internally, with the growth of the corneal lens and the associated retina up to an age of about 20 days. This has not been previously observed in an insect. The use of this characteristic for recognising young adults of this species is suggested.

Novel relationship between Vegf expression and retinal pigmented epithelium permeability following light damage in the mouse retina

Purpose:In the retina, the balance between pro- and anti-angiogenic factors is critical for angiogenesis control but is also involved in cell survival and maintenance. For instance, the anti-angiogenic factor PEDF is neuroprotective for photoreceptors (PRs) in models of retinal degeneration. We previously reported upregulation of VEGF (24h to 48h post lesion) in the light-damage (LD) model. Furthermore, systemic delivery of PEDF, as well as lentiviral gene transfer of an anti-VEGF antibody rescue PRs from cell death. Studies in vitro show that VEGF induces retinal endothelial cells apoptosis via the alteration of the Akt1/p38 MAPK signalling pathway under hypoxic conditions. Thus, in this study, we investigate the effect of high levels of VEGF on retinal pigmented epithelium (RPE) permeability and molecular targets expression after light-induced PR degeneration. Methods:To characterize the action of VEGF in the retina during the course of LD, we exposed adult Balb/c mice to 5'000 lux for 1h, and we collected neural retinas and eye-cups (containing RPE) at different time points after the LD. We analysed protein expression by Elisa and Western blotting. In order to study RPE cell permeability after the LD we stained β-catenin on flat mounted RPE. Results:In the neural retina, preliminary results indicate that high levels of VEGF induce a significant upregulation of VEGF receptor 2, whereas VEGF receptor 1 expression is decreased. Concomitantly with VEGF upregulation, LD increases the Src phosphorylation between 24h to 48h. Furthermore, we observe that β-catenin translocates to the cytoplasm of RPE cells between 24h to 36h after the lesion, indicating an increase on the RPE permeability, which could contribute indirectly to the deleterious effect of VEGF observed during light-induced PR apoptosis. Conclusions:This study further involves VEGF in LD and highlights the prime importance of angiogenic factor balance for PR survival. Our results suggest that PR apoptosis is augmented by RPE cell permeability, which may induce high level of VEGF and could be deleterious. The specific action of RPE permeability on PR survival and the role of Src in the retina are under investigation.

Melanopsin as a sleep modulator: circadian gating of the direct effects of light on sleep and altered sleep homeostasis in Opn4(-/-) mice.

Light influences sleep and alertness either indirectly through a well-characterized circadian pathway or directly through yet poorly understood mechanisms. Melanopsin (Opn4) is a retinal photopigment crucial for conveying nonvisual light information to the brain. Through extensive characterization of sleep and the electrocorticogram (ECoG) in melanopsin-deficient (Opn4(-/-)) mice under various light-dark (LD) schedules, we assessed the role of melanopsin in mediating the effects of light on sleep and ECoG activity. In control mice, a light pulse given during the habitual dark period readily induced sleep, whereas a dark pulse given during the habitual light period induced waking with pronounced theta (7-10 Hz) and gamma (40-70 Hz) activity, the ECoG correlates of alertness. In contrast, light failed to induce sleep in Opn4(-/-) mice, and the dark-pulse-induced increase in theta and gamma activity was delayed. A 24-h recording under a LD 1-hratio1-h schedule revealed that the failure to respond to light in Opn4(-/-) mice was restricted to the subjective dark period. Light induced c-Fos immunoreactivity in the suprachiasmatic nuclei (SCN) and in sleep-active ventrolateral preoptic (VLPO) neurons was importantly reduced in Opn4(-/-) mice, implicating both sleep-regulatory structures in the melanopsin-mediated effects of light. In addition to these acute light effects, Opn4(-/-) mice slept 1 h less during the 12-h light period of a LD 12ratio12 schedule owing to a lengthening of waking bouts. Despite this reduction in sleep time, ECoG delta power, a marker of sleep need, was decreased in Opn4(-/-) mice for most of the (subjective) dark period. Delta power reached after a 6-h sleep deprivation was similarly reduced in Opn4(-/-) mice. In mice, melanopsin's contribution to the direct effects of light on sleep is limited to the dark or active period, suggesting that at this circadian phase, melanopsin compensates for circadian variations in the photo sensitivity of other light-encoding pathways such as rod and cones. Our study, furthermore, demonstrates that lack of melanopsin alters sleep homeostasis. These findings call for a reevaluation of the role of light on mammalian physiology and behavior.

A pea plasma membrane protein exhibiting blue light-induced phosphorylation retains photosensitivity following triton solubilization.

Phosphorylation of a polypeptide of approximately 120 kD in pea (Pisum sativum L.) plasma membranes in response to blue light has been shown to be involved in phototropic curvature, but the relationship of this protein to the kinase and photoreceptor acting upon it is uncertain. Using two-phase aqueous partitioning to isolate right-side-out plasma membrane vesicles, we have obtained evidence suggesting that the photoreceptor, kinase, and substrate are localized to the plasma membrane fraction. Latent phosphorylation accessible through Triton X-100 or freeze/thaw treatments of purified plasma membrane vesicles indicates that at least the kinase moiety is present on the internal face of the plasma membrane. Effects of solubilization of vesicles on fluence-response characteristics and on phosphorylation levels provide evidence that the receptor, kinase, and protein substrate are present together in individual mixed detergent micelles, either as a stable complex or as domains of a single polypeptide. In vivo blue-light irradiation results in a small but significant decrease in mobility of the 120-kD phosphorylated protein on sodium dodecylsulfate gel electrophoresis. This mobility shift is evident on Coomassie-stained gels and on western blots probed with polyclonal antibodies raised against the 120-kD protein. Among the plasma membrane proteins bound to the reactive nucleotide analog fluorosulfonylbenzoyladenine (FSBA), a distinct protein band at 120 kD can be detected on blots probed with anti-FSBA antibodies. This band exhibits an in vivo light-dependent mobility shift identical to that observed for the protein band and antibodies specific for the 120-kD protein, implying that the 120-kD protein has an integral nucleotide binding site and consistent with the possibility that the substrate protein is also a kinase.

Light receptor action is critical for maintaining plant biomass at warm ambient temperatures.

The ability to withstand environmental temperature variation is essential for plant survival. Former studies in Arabidopsis revealed that light signalling pathways had a potentially unique role in shielding plant growth and development from seasonal and daily fluctuations in temperature. In this paper we describe the molecular circuitry through which the light receptors cry1 and phyB buffer the impact of warm ambient temperatures. We show that the light signalling component HFR1 acts to minimise the potentially devastating effects of elevated temperature on plant physiology. Light is known to stabilise levels of HFR1 protein by suppressing proteasome-mediated destruction of HFR1. We demonstrate that light-dependent accumulation and activity of HFR1 are highly temperature dependent. The increased potency of HFR1 at warmer temperatures provides an important restraint on PIF4 that drives elongation growth. We show that warm ambient temperatures promote the accumulation of phosphorylated PIF4. However, repression of PIF4 activity by phyB and cry1 (via HFR1) is critical for controlling growth and maintaining physiology as temperatures rise. Loss of this light-mediated restraint has severe consequences for adult plants which have greatly reduced biomass.

Daisy Roots Garden Project

In the summer of 2009 a local Men’s group that met in St Helena’s thought that it might be a good idea to sow a wild garden on the site.  Then came the raised beds – 2 were placed in the garden area opposite the front door of the house and as it was winter there was not much happening and they were quickly renamed the ‘coffins’.  This was the start of ‘Daisy Roots’. Dublin City Council provided top soil and water butts.  An Taisce funded the start up phase of the project and now continue to provide funds for insurance and some development work.  At the right hand side of St Helena’s there is, what was the old stable yard of the ‘big house’.  This had been used to house a large ‘lock up container and a porta-cabin.  These have been now removed and this is where the main part of the garden is. Following a conference of Business in the Community Ireland, DX Ltd expressed an interest in getting involved in a local project.  Together DX staff and the volunteers reclaimed the old stables and gave them new roofs and new doors.  Paths were put in between the raised vegetable beds and new raised beds were built.  A seating area was developed.  The garden is now wheelchair accessible and there are wheelchair accessible flowerbeds in the garden also.  The newest projects in the garden are a memorial flowerbed and a propagator. Dublin City Council via Cherry Orchard Regeneration Board Initiative Type Community Food Growing Projects Location Dublin 11 Funding Dublin City Council via Cherry Orchard Regeneration Board Partner Agencies An Taisce Dublin City Council HSE Tolka Area Partnership

Lutzomyia longipalpis in Clorinda, Formosa province, an area of potential visceral leishmaniasis transmission in Argentina

Phlebotomine captures were performed during 2004 in Clorinda, Argentina. Clorinda is located across the branches of the Paraguay river in front of Asunción city, Paraguay. Reports of canine and human visceral leishmaniasis in Asunción have been increasing since 1997, however neither leishmaniasis cases nor sand flies were ever recorded from Clorinda. Light traps were located in migration paths (bridges, port), and peridomestic environments of Clorinda and surrounding localities. Lutzomyia longipalpis was found in Clorinda and Puerto Pilcomayo, first report in a potential visceral leishmaniasis transmission area for Argentina. Active surveillance is required immediately in the localities involved and the surrounding area.

Warm Front, Better Health: Health Impact Evaluation of the Warm Front Scheme

About 4 million households in the UK cannot adequately heat their homes in winter due to low income and poor quality housing, the two main causes of fuel poverty. The primary impact of fuel poverty is cold homes in winter which can lead to various health problems and even death among the vulnerable young and the elderly population. The government launched the Warm Front scheme in 2000 to tackle fuel poverty among the vulnerable households in England by providing energy efficiency measures in the forms insulation and modern heating system(??). By 2004, about 770,000 households had benefited from the Warm Front scheme and a total of 2 million households are still expected to benefit by 2010. Since 2001, the Bartlett has been investigating with London School of Hygiene & Tropical Medicine and Sheffield Hallam University, the health and the environmental impact of the Warm Front scheme. This investigative study is the most detailed to date on fuel poor dwellings based on detailed surveys of household and dwelling data, fuel consumption record and monitored temperature and relative humidity from 3,100 dwellings before and after the energy efficiency measures. The Warm Front investigation was expected to continue until the end of 2007. The findings from the investigation indicated that the Warm Front scheme was likely to have benefits in terms of improved thermal comfort and well-being as a result of mean temperature rise of 1.6C in the living room and 2.8C in the bedroom. Warm Front also lead to a decrease in indoor relative humidity mainly from the increased temperature since there appeared to be little impact on vapour pressure from changes in air tightness. Pressure test results indicated that the effects of air tightness measures such as draught stripping and cavity wall insulation were offset by the installation of a central heating system, particularly when the pipe work feeding radiators was installed below timber floors.