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- Abdusselamoglu, MD, et al.
(författare)
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Dynamics of activating and repressive histone modifications in Drosophila neural stem cell lineages and brain tumors
- 2019
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Ingår i: Development (Cambridge, England). - : The Company of Biologists. - 1477-9129 .- 0950-1991. ; 146:23
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Tidskriftsartikel (refereegranskat)abstract
- During central nervous system (CNS) development, spatiotemporal gene expression programs mediate specific lineage decisions to generate neuronal and glial cell types from neural stem cells (NSCs). However, little is known about the epigenetic landscape underlying these highly complex developmental events. Here, we perform ChIP-seq on distinct subtypes of Drosophila FACS- purified neural stem cells (NSCs) and their differentiated progeny to dissect the epigenetic changes accompanying the major lineage decisions in vivo. By analyzing active and repressive histone modifications, we show that stem cell identity genes are silenced during differentiation by loss of their activating marks and not via repressive histone modifications. Our analysis also uncovers a new set of genes specifically required for altering lineage patterns in type II neuroblasts, one of the two main Drosophila NSC identities. Finally, we demonstrate that this subtype specification in NBs, unlike NSC differentiation, requires Polycomb-group (PcG)-mediated repression.
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- Miller, Hayley V., et al.
(författare)
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The mirror-based eyes of scallops demonstrate a light-evoked pupillary response
- 2019
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 29:9, s. 313-314
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Tidskriftsartikel (refereegranskat)abstract
- Light levels in terrestrial and shallow-water environments can vary by ten orders of magnitude between clear days and overcast nights. Light-evoked pupillary responses help the eyes of animals perform optimally under these variable light conditions by balancing trade-offs between sensitivity and resolution [1]. Here, we document that the mirror-based eyes of the bay scallop Argopecten irradians and the sea scallop Placopecten magellanicus have pupils that constrict to ∼60% of their fully dilated areas within several minutes of light exposure. The eyes of scallops contain two separate retinas and our ray-tracing model indicates that, compared to eyes with fully constricted pupils, eyes from A. irradians with fully dilated pupils provide approximately three times the sensitivity and half the spatial resolution at the distal retina and five times the sensitivity and one third the spatial resolution at the proximal retina. We also identify radial and circular actin fibers associated with the corneas of A. irradians that may represent muscles whose contractions dilate and constrict the pupil, respectively. Miller et al. report that the mirror-based eyes of two species of scallop have pupils that constrict to ∼60% of their fully dilated areas within several minutes of being exposed to light. At the cost of sensitivity, narrower pupils improve spatial resolution in the eyes of scallops by decreasing the influence of optical aberrations.
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- Steinthorsdottir, Margret, et al.
(författare)
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Cuticle surfaces of fossil plants as a potential proxy for volcanic SO2 emissions: observations from the Triassic-Jurassic transition of East Greenland
- 2018
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Ingår i: Palaeobiodiversity and Palaeoenvironments. - Berlin : Springer. - 1867-1594 .- 1867-1608. ; 98:1, s. 49-69
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Tidskriftsartikel (refereegranskat)abstract
- Flood basalt volcanism has been implicated in several episodes of mass extinctions and environmental degradation in the geological past, including at the Triassic–Jurassic (Tr–J) transition, through global warming caused by massive outgassing of carbon dioxide. However, the patterns of biodiversity loss observed are complicated and sometimes difficult to reconcile with the effects of global warming alone. Recently, attention has turned to additional volcanic products as potential aggravating factors, in particular sulphur dioxide (SO2). SO2 acts both directly as a noxious environmental pollutant and indirectly through forming aerosols in the atmosphere, which may cause transient global dimming and cooling. Here, we present a range of morphological changes to fossil plant leaf cuticle surfaces of hundreds of Ginkgoales and Bennettitales specimens across the Tr–J boundary of East Greenland. Our results indicate that morphological structures of distorted cuticles near the Tr–J boundary are consistent with modern cuticle SO2-caused damage and supported by recent leaf-shape SO2 proxy results, thus identifying cuticle surface morphology as a potentially powerful proxy for SO2. Recording the timing and duration of SO2 emissions in the past may help distinguish between the driving agents responsible for mass extinction events and thus improve our understanding of the Earth System.
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