Extended chromatin fibers and chromatin organization

Abstract

Studies of chromatin extensibility have revealed the flow of chromatin and DNA from cell nuclei and chromosomes in response to gravity or mechanical stretch following lysis by hypertonic saline and detergent solutions. Since this phenomenon was first reported, the technical methods by which extended chromatin fibers (ECFs) may be analyzed have been improved. These methods include topochemical assays, fluorescence in situ hybridization, immunofluorescence, electron microscopy, and polarization microscopy. Chromatin and DNA "halos" also have been studied in materials subjected to lysis, especially in a horizontal position or after cytocentrifugation. The analysis of ECF formation is useful not only as a tool for detecting the positioning of certain DNA signals on chromatin filaments, but also for describing diverse DNA-protein associations that may be related to varying transcriptional activities and chromatin supraorganization. A brief review of the methods and applications of ECF formation is presented here. We focus on light microscopy studies of ECF formation in mouse hepatocytes under different chromatin supraorganization and physiological conditions and in sperm cells with different DNA-protein complexes.

Polyploidy and chromatin remodeling in hepatocytes from insulin‐dependent diabetic and normoglycemic aged mice

“…However, the increase in the Feulgen-DNA amounts in aged BALB/ c mice compared with the adult controls was not as substantial as the increase observed for the diabetic NOD mice. We propose that this result is because the genomic effects for the 56-week-old BALB/c mice are not totally comparable to the diabetic conditions in the NOD mice or because the BALB/c female mice at this age do not fully represent advanced aging, as reported for instance in A/Uni male mice (27). If considering epigenetic markers to the genome, the age-related dysregulation of cytosine methylation that occurs in the rat and mouse liver (28À30) is not fully comparable to the pattern (cytosine hypomethylation) reported for liver cells from Type 1 diabetic rat (24).…”

Atomic force microscopy on chromosomes, chromatin and DNA: A review

“…2). Since new preparation techniques like Fluorescent In Situ Hybridisation on stretched DNA fibres (fibre-FISH) and related extended DNA preparations (reviewed extensively in Mello et al, 2011) became popular as well, the use of the AFM for ISH on chromosomes became less and less attractive. Near field Scanning Optical Microscopy (NSOM) has taken a more important role as it combines the high resolution of Scanning force Microscopy with the ease and high resolution of FISH (see for an early example M.H.P.…”

Ação do ácido valproico e da tricostatina A na organização cromatínica e sua regulação por fatores epigenéticos em células HepG2 sob condições de hiperglicemia

“…Atua ainda na produção de proteínas das cascatas sinalizadoras do sistema imune, como o sistema complemento, e das proteínas do sistema de coagulação (Qin e Gao, 2006). Além disso, os hepatócitos apresentam fenótipo nuclear que responde a diversas situações metabólicas, como o jejum e o envelhecimento, com alterações na supraorganização cromatínica (Moraes et al 2005;Mello et al, 2011;. Dessa forma, trata-se de um ambiente importante para estudo da ação de HDACis, como o VPA e a TSA, em condições de hiperglicemia do ponto de vista da remodelação da cromatina e de sua regulação por fatores epigenéticos.…”