CTCF knockout in zebrafish induces alterations in regulatory landscapes and developmental gene expression

Coordinated chromatin interactions between enhancers and promoters are critical for gene regulation. The architectural protein CTCF mediates chromatin looping and is enriched at the boundaries of topologically associating domains (TADs), which are sub-megabase chromatin structures. In vitro CTCF depletion leads to a loss of TADs but has only limited effects over gene expression, challenging the concept that CTCF-mediated chromatin structures are a fundamental requirement for gene regulation. However, how CTCF and a perturbed chromatin structure impacts gene expression during development remains poorly understood. Here we link the loss of CTCF and gene regulation during patterning and organogenesis in a ctcf knockout zebrafish model. CTCF absence leads to loss of chromatin structure and affects the expression of thousands of genes, including many developmental regulators. Our results demonstrate the essential role of CTCF in providing the structural context for enhancer-promoter interactions, thus regulating developmental genes

The little skate genome and the evolutionary emergence of wing-like fin appendages

Skates are cartilaginous fish whose novel body plan features remarkably enlarged wing-like pectoral fins that allow them to thrive in benthic environments. The molecular underpinnings of this unique trait, however, remain elusive. Here we investigate the origin of this phenotypic innovation by developing the little skate Leucoraja erinacea as a genomically enabled model. Analysis of a high-quality chromosome-scale genome sequence for the little skate shows that it preserves many ancestral jawed vertebrate features compared with other sequenced genomes, including numerous ancient microchromosomes. Combining genome comparisons with extensive regulatory datasets in developing fins (gene expression, chromatin occupancy and three-dimensional (3D) conformation) we find skate-specific genomic rearrangements that alter the 3D regulatory landscape of genes involved in the planar cell polarity (PCP) pathway. Functional inhibition of PCP signaling resulted in marked reduction of anterior fin size, confirming this pathway as a major contributor of batoid fin morphology. We also identified a fin-specific enhancer that interacts with 3' HOX genes, consistent with the redeployment of Hox gene expression in anterior pectoral fins, and confirmed the potential of this element to activate transcription in the anterior fin using zebrafish reporter assays. Our findings underscore the central role of genome reorganizations and regulatory variation in the evolution of phenotypes, shedding light on the molecular origin of an enigmatic trait

Dynamics of enhancer chromatin signatures mark the transition from pluripotency to cell specification during embryogenesis

Contains fulltext : 103309.pdf (publisher's version ) (Open Access

Characterization of a triboelectric x-ray spectrum

Nowadays, sintering is a very useful technique to fabricate metal, ceramic and composites parts for different applications. This phenomenon has been extensively studied over 50 years and, most of the research related to it used a model based on two contacting particles. However, just a few jobs were focused on the powder sintering on a solid substrate. This work investigates the effect of two parameters; substrate shape and inclusion of the reinforced particles on the evolving microstructure during sintering of particles on a rigid substrate. Powders and solid bars of copper are used as a model material and particles such as tungsten carbide (WC) as reinforcing particles. Sintering was performed in an electrical furnace at 1050 °C under reducing atmosphere. The progress on sintering was evaluated by measuring the relative density close and far from the solid substrate by means of the image analysis from pictures taken by scanning electronic microscope (SEM). The effects on the constraint sintering were also identified. Heterogeneous densification and delamination of the film from the substrate were observed as densification increased which by the way is reduced by the inclusion of the reinforced particles. " (2014) Trans Tech Publications, Switzerland.",,,,,,,,,"http://hdl.handle.net/20.500.12104/39990","http://www.scopus.com/inward/record.url?eid=2-s2.0-84904573603&partnerID=40&md5=f5231656cbef31653fa886e78e90c0c5",,,,,,,,"Materials Science Forum",,"13

Characterization of constrained sintering of powders on solid substrate

Nowadays, sintering is a very useful technique to fabricate metal, ceramic and composites parts for different applications. This phenomenon has been extensively studied over 50 years and, most of the research related to it used a model based on two contacting particles. However, just a few jobs were focused on the powder sintering on a solid substrate. This work investigates the effect of two parameters; substrate shape and inclusion of the reinforced particles on the evolving microstructure during sintering of particles on a rigid substrate. Powders and solid bars of copper are used as a model material and particles such as tungsten carbide (WC) as reinforcing particles. Sintering was performed in an electrical furnace at 1050 °C under reducing atmosphere. The progress on sintering was evaluated by measuring the relative density close and far from the solid substrate by means of the image analysis from pictures taken by scanning electronic microscope (SEM). The effects on the constraint sintering were also identified. Heterogeneous densification and delamination of the film from the substrate were observed as densification increased which by the way is reduced by the inclusion of the reinforced particles. © (2014) Trans Tech Publications, Switzerland

Characterization of constrained sintering of powders on solid substrate

Nowadays, sintering is a very useful technique to fabricate metal, ceramic and composites parts for different applications. This phenomenon has been extensively studied over 50 years and, most of the research related to it used a model based on two contacting particles. However, just a few jobs were focused on the powder sintering on a solid substrate. This work investigates the effect of two parameters; substrate shape and inclusion of the reinforced particles on the evolving microstructure during sintering of particles on a rigid substrate. Powders and solid bars of copper are used as a model material and particles such as tungsten carbide (WC) as reinforcing particles. Sintering was performed in an electrical furnace at 1050 �C under reducing atmosphere. The progress on sintering was evaluated by measuring the relative density close and far from the solid substrate by means of the image analysis from pictures taken by scanning electronic microscope (SEM). The effects on the constraint sintering were also identified. Heterogeneous densification and delamination of the film from the substrate were observed as densification increased which by the way is reduced by the inclusion of the reinforced particles. � (2014) Trans Tech Publications, Switzerland

An ancient genomic regulatory block conserved across bilaterians and its dismantling in tetrapods by retrogene replacement

10.1101/gr.132233.111Genome Research224642-655GERE

Autonomy through SLAM for an Underwater Robot

Abstract An autonomous underwater vehicle (AUV) is achieved that integrates state of the art simultaneous localization and mapping (SLAM) into the decision processes. This autonomy is used to carry out undersea target reacquisition missions that would otherwise be impossible with a low-cost platform. The AUV requires only simple sensors and operates without navigation equipment such as Doppler Velocity Log, inertial navigation or acoustic beacons. Demonstrations of the capability show that the vehicle can carry out the task in an ocean environment. The system includes a forward looking sonar and a set of simple vehicle sensors. The functionality includes feature tracking using a graphical square root smoothing SLAM algorithm, global localization using multiple EKF estimators, and knowledge adaptive mission execution. The global localization incorporates a unique robust matching criteria which utilizes both positive and negative information. Separate match hypotheses are maintained by each EKF estimator allowing all matching decisions to be reversible.