scholarly journals Analysis of Complex DNA Rearrangements during Early Stages of HAC Formation

2020 ◽  
Vol 9 (12) ◽  
pp. 3267-3287
Author(s):  
Elisa Pesenti ◽  
Mikhail Liskovykh ◽  
Koei Okazaki ◽  
Alessio Mallozzi ◽  
Caitlin Reid ◽  
...  
Keyword(s):  
Dna Rearrangements ◽  
Early Stages

scholarly journals Analysis of Complex DNA Rearrangements During Early Stages of HAC Formation

2020 ◽  
Author(s):  
Elisa Pesenti ◽  
Mikhail Liskovykh ◽  
Koei Okazaki ◽  
Alessio Mallozzi ◽  
Caitlin Reid ◽  
...  
Keyword(s):  
Genomic Organization ◽  
Cell Clone ◽  
Chromosome Instability ◽  
Human Chromosomes ◽  
Dna Rearrangements ◽  
Structural Domains ◽  
Artificial Chromosomes ◽  
Early Stages ◽  
Ht1080 Cells ◽  
Cancer Types

AbstractHuman Artificial Chromosomes (HACs) are important tools for epigenetic engineering, for measuring chromosome instability (CIN) and possible gene therapy. However, their use in the latter is potentially limited because the input HAC-seeding DNA can undergo an unpredictable series of rearrangements during HAC formation. As a result, after transfection and HAC formation, each cell clone contains a HAC with a unique structure that cannot be precisely predicted from the structure of the HAC-seeding DNA. Although it has been reported that these rearrangements can happen, the timing and mechanism of their formation has yet to be described. Here we synthesized a HAC-seeding DNA with two distinct structural domains and introduced it into HT1080 cells. We characterized a number of HAC-containing clones and subclones to track DNA rearrangements during HAC establishment. We demonstrated that rearrangements can occur early during HAC formation. Subsequently, the established HAC genomic organization is stably maintained across many cell generations. Thus, early stages in HAC formation appear to at least occasionally involve a process of DNA shredding and shuffling that resembles chromothripsis, an important hallmark of many cancer types. Understanding these events during HAC formation has critical implications for future efforts aimed at synthesizing and exploiting synthetic human chromosomes.

Spherulitic crystal growth in the prodissoconch larval of Crassostrea virginica

1983 ◽  
Vol 41 ◽  
pp. 518-519
Author(s):  
George G. Cocks ◽  
Louis Leibovitz ◽  
DoSuk D. Lee
Keyword(s):  
Crystal Structure ◽  
Crassostrea Virginica ◽  
Crystal Orientation ◽  
Developmental Changes ◽  
Gastrula Stage ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Stages Of Growth ◽  
Early Stages ◽  
Initial Deposition

Our understanding of the structure and the formation of inorganic minerals in the bivalve shells has been considerably advanced by the use of electron microscope. However, very little is known about the ultrastructure of valves in the larval stage of the oysters. The present study examines the developmental changes which occur between the time of conception to the early stages of Dissoconch in the Crassostrea virginica(Gmelin), focusing on the initial deposition of inorganic crystals by the oysters.The spawning was induced by elevating the temperature of the seawater where the adult oysters were conditioned. The eggs and sperm were collected separately, then immediately mixed for the fertilizations to occur. Fertilized animals were kept in the incubator where various stages of development were stopped and observed. The detailed analysis of the early stages of growth showed that CaCO3 crystals(aragonite), with orthorhombic crystal structure, are deposited as early as gastrula stage(Figuresla-b). The next stage in development, the prodissoconch, revealed that the crystal orientation is in the form of spherulites.

Formation of Dislocation Channels in Neutron Irradiated Molybdenum

1972 ◽  
Vol 30 ◽  
pp. 672-673
Author(s):  
S. Mahajan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ambient Temperature ◽  
Room Temperature ◽  
Channel Formation ◽  
Early Stages ◽  
Transmission Electron ◽  
Three Stages ◽  
Two Stages ◽  
Polycrystalline Molybdenum

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.

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