Abstract:We succeeded in visualizing the spatial distribution of the local elasticity of mitotic human chromosomes in a liquid environment using scanning probe microscopy (SPM). Force-versus-indentation curves (force curves) were collected over an entire single chromosome. To estimate the local elasticity of thin chromosomes from the force curves, we examined the validity of a previously proposed model that takes into account the effect of the finite thickness of samples on the estimation of the local elasticity. The f… Show more
“…The paired chromatids are often connected with entangled chromatin fibers, suggesting the presence of the catenation even in the metaphase chromosome (Hoshi et al 2007b. ) images obtained by this method can visualize differences in surface stiffness or local elasticity of single human chromosomes (Nomura et al 2005;Kawabata et al 2007). On the other hand, AFM combined with scanning near-field optical microscopy (SNOM), or SNOM/AFM is one of the candidates for an attractive tool for the study of chromosomes, because it can collect both topographic and fluorescence images of the same portion of the samples simultaneously (Iwabuchi et al 1997;Yoshino et al 2002.…”
The present study introduces the principle of atomic force microscopy (AFM) and reviews our results of human metaphase chromosomes obtained by AFM. AFM imaging of the chromosomes revealed that the chromatid arm was not uniform in structure but had ridges and grooves along its length, which was most prominent in the late metaphase. The arrangement of these ridges and grooves was roughly symmetrical with the counterpart of the paired sister chromatids. AFM imaging of banded chromosomes also showed that the ridges and grooves were related to the G/Q-positive and G/Q-negative bands, respectively. At high magnification, the chromatid was seen to be produced by the compaction of highly twisted chromatin fiber loops, and its compaction tended to be stronger in the ridged regions of the chromosomes than in the grooved regions. Our AFM studies also showed the presence of catenation of chromatin fibers between the ridged portions of the chromatid in the late metaphase. Thus, AFM is useful for obtaining the three-dimensional surface topography not only in ambient conditions but also in physiological liquid conditions, and is expected to be an attractive tool for investigating the structure of chromosomes.
“…The paired chromatids are often connected with entangled chromatin fibers, suggesting the presence of the catenation even in the metaphase chromosome (Hoshi et al 2007b. ) images obtained by this method can visualize differences in surface stiffness or local elasticity of single human chromosomes (Nomura et al 2005;Kawabata et al 2007). On the other hand, AFM combined with scanning near-field optical microscopy (SNOM), or SNOM/AFM is one of the candidates for an attractive tool for the study of chromosomes, because it can collect both topographic and fluorescence images of the same portion of the samples simultaneously (Iwabuchi et al 1997;Yoshino et al 2002.…”
The present study introduces the principle of atomic force microscopy (AFM) and reviews our results of human metaphase chromosomes obtained by AFM. AFM imaging of the chromosomes revealed that the chromatid arm was not uniform in structure but had ridges and grooves along its length, which was most prominent in the late metaphase. The arrangement of these ridges and grooves was roughly symmetrical with the counterpart of the paired sister chromatids. AFM imaging of banded chromosomes also showed that the ridges and grooves were related to the G/Q-positive and G/Q-negative bands, respectively. At high magnification, the chromatid was seen to be produced by the compaction of highly twisted chromatin fiber loops, and its compaction tended to be stronger in the ridged regions of the chromosomes than in the grooved regions. Our AFM studies also showed the presence of catenation of chromatin fibers between the ridged portions of the chromatid in the late metaphase. Thus, AFM is useful for obtaining the three-dimensional surface topography not only in ambient conditions but also in physiological liquid conditions, and is expected to be an attractive tool for investigating the structure of chromosomes.
“…Atomic force microscopy (AFM) (topography) imaging of stained G band patterns of the chromosomes was used to investigate the possibility of obtaining better resolution of the bands (5). Other reports of SPM applications on chromosomes include near-field scanning optical microscopy measurements of the bands (6) and elasticity investigation of chromosome structure (7). One SPM method, scanning conductance microscopy (SCM), has in recent years been used to map out different properties of nano-sized particles, for example, the dielectric constant of nanoparticles of poly(ethylene oxide) (8), the conductance of carbon nanotubes and DNA (9), and trapped charges on a surface by carbon nanotubes (10).…”
Scanning conductance microscopy investigations were carried out in air on human chromosomes fixed on pre-fabricated SiO2 surfaces with a backgate. The point of the investigation was to estimate the dielectric constant of fixed human chromosomes in order to use it for microfluidic device optimization. The phase shift caused by the electrostatic forces, together with geometrical measurements of the atomic force microscopy (AFM) cantilever and the chromosomes were used to estimate a value for the dielectric constant of different human chromosomes.
“…Compared to these stretching experiments, AFM indentation experiments measured dramatically larger Young's modulus for human mitotic chromosomes ( E = 0.39 MPa (Jiao and Schäffer, 2004) and E = 5–50 kPa (Nomura et al ., 2005), Fig. 4).…”
Section: Mechanical Characterization Of Mitotic Chromosomesmentioning
confidence: 91%
“…One advantage of AFM is that it allows to generate a map of elastic properties by scanning over the chromosome, which unveiled large inhomogeneities in the Young's modulus with variations over one order of magnitude (Fig. 4) (Jiao and Schäffer, 2004; Nomura et al ., 2005). Fig.…”
Section: Mechanical Characterization Of Mitotic Chromosomesmentioning
Condensation and faithful separation of the genome are crucial for the cellular life cycle. During chromosome segregation, mechanical forces generated by the mitotic spindle pull apart the sister chromatids. The mechanical nature of this process has motivated a lot of research interest into the mechanical properties of mitotic chromosomes. Although their fundamental mechanical characteristics are known, it still remains unclear how these characteristics emerge from the structure of the mitotic chromosome. Recent advances in genomics, computational and super-resolution microscopy techniques have greatly promoted our understanding of the chromosomal structure and have motivated us to review the mechanical characteristics of chromosomes in light of the current structural insights. In this review, we will first introduce the current understanding of the chromosomal structure, before reviewing characteristic mechanical properties such as the Young's modulus and the bending modulus of mitotic chromosomes. Then we will address the approaches used to relate mechanical properties to the structure of chromosomes and we will also discuss how mechanical characterization can aid in elucidating their structure. Finally, future challenges, recent developments and emergent questions in this research field will be discussed.
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