ABSTRACT
The chromatin architecture is constantly changing because of cellular processes such as proliferation, differentiation and changes in the expression profile during gene activation or silencing. Unravelling the changes that occur in the chromatin structure during these processes has been a topic of interest for many years. It is known that gene activation of large gene loci is thought to occur by means of an active looping mechanism. It was also shown for the ß-globin locus that the gene promoter interacts with an active chromatin hub by means of an active looping mechanism. This means that the locus changes in three-dimensional (3D) nuclear volume and chromatin shape. As a means of visualizing and measuring these dynamic changes in chromatin structure of the ß-globin locus, we used a 3D DNA-FISH method in combination with 3D image acquisition to volume render fluorescent signals into 3D objects. These 3D chromatin structures were geometrically analysed, and results prior to and after gene activation were quantitatively compared. Confocal and super-resolution imaging revealed that the inactive locus occurs in several different conformations. These conformations change in shape and surface structure upon cell differentiation into a more folded and rounded structure that has a substantially smaller size and volume. These physical measurements represent the first non-biochemical evidence that, upon gene activation, an actively transcribing chromatin hub is formed by means of additional chromatin looping.
Subject(s)
Genetic Loci/genetics , Imaging, Three-Dimensional/methods , Nucleic Acid Conformation , Transcriptional Activation , beta-Globins/chemistry , beta-Globins/genetics , Animals , Cell Line , Chromatin/chemistry , Chromatin/genetics , DNA/chemistry , In Situ Hybridization, Fluorescence , Mice , Microscopy, Confocal , Microspheres , Models, BiologicalABSTRACT
The purpose of this study was to explore the effects of handedness on coordination of grip (G) and load (L) forces in static bimanual manipulation tasks. Participants (N = 10) exerted various L profiles against an externally fixed hand-held device based on presumably open-loop and closed-loop neural control mechanisms, (i.e., mediated and not mediated, respectively, by sensory feedback). Average G/L ratio and the coupling of G and L (i.e., stability of the G/L ratio and correlation between G and L) were separately assessed in each hand. The results revealed a lower average G/L ratio in the non-dominant hand suggesting a more economical grip, while the indices of G and L coupling were similar in two hands. The dominant and non-dominant hand failed to reveal relative advantages in the tasks predominantly based on open- and closed-loop control mechanisms, respectively. We conclude that, due to the static nature of the tested tasks, the particular advantage of the non-dominant hand in G and L coordination could be in line with the recently proposed specialization of the non-dominant limb for control of position. However, the overall results are not in line with classic views of the prevailing open- closed-loop neural mechanisms in the control of the dominant and nondominant limb, respectively.
