Polymerase chain reaction-based suppression of repetitive sequences in whole chromosome painting probes for FISH

Application of Fluorescence In Situ Hybridization (FISH) in Oral Microbial Detection

Varieties of microorganisms reside in the oral cavity contributing to the occurrence and development of microbes associated with oral diseases; however, the distribution and in situ abundance in the biofilm are still unclear. In order to promote the understanding of the ecosystem of oral microbiota and the diagnosis of oral diseases, it is necessary to monitor and compare the oral microorganisms from different niches of the oral cavity in situ. The fluorescence in situ hybridization (FISH) has proven to be a powerful tool for representing the status of oral microorganisms in the oral cavity. FISH is one of the most routinely used cytochemical techniques for genetic detection, identification, and localization by a fluorescently labeled nucleic acid probe, which can hybridize with targeted nucleic acid sequences. It has the advantages of rapidity, safety, high sensitivity, and specificity. FISH allows the identification and quantification of different oral microorganisms simultaneously. It can also visualize microorganisms by combining with other molecular biology technologies to represent the distribution of each microbial community in the oral biofilm. In this review, we summarized and discussed the development of FISH technology and the application of FISH in oral disease diagnosis and oral ecosystem research, highlighted its advantages in oral microbiology, listed the existing problems, and provided suggestions for future development..

Human metaphase chromosome consists of randomly arranged chromatin fibres with up to 30-nm diameter

During cell division, mitotic chromosomes assemble and are equally distributed into two new daughter cells. The chromosome organisation of the two chromatids is essential for even distribution of genetic materials. Although the 11-nm fibre or nucleosome structure is well-understood as a fundamental fibrous structure of chromosomes, the reports on organisation of 30-nm basic chromatin fibres have been controversial, with debates on the contribution of 30-nm or thicker fibres to the higher order inner structure of chromosomes. Here, we used focused ion beam/scanning electron microscopy (FIB/SEM) to show that both 11-nm and 30-nm fibres are present in the human metaphase chromosome, although the higher-order periodical structure could not be detected under the conditions employed. We directly dissected the chromosome every 10-nm and observed 224 cross-section SEM images. We demonstrated that the chromosome consisted of chromatin fibres of an average diameter of 16.9-nm. The majority of the chromatin fibres had diameters between 5 and 25-nm, while those with 30-nm were in the minority. The reduced packaging ratio of the chromatin fibres was detected at axial regions of each chromatid. Our results provide a strong basis for further discussions on the chromosome higher-order structure.

Development of locus specific sub-clone separation by fluorescence in situ hybridization in suspension in chronic lymphocytic leukemia

Intra-tumor genetic heterogeneity is a hallmark of cancer. The ability to monitor and analyze these sub-clonal cell populations can be considered key to successful treatment, particularly in the modern era of targeted therapies. Although advances in sequencing technologies have significantly improved our ability to analyze the mutational landscape of tumors, this utility is reduced when considering small, but clinically significant sub-clones, that is, those representing <10% of the tumor burden. We have developed a high-throughput method that utilizes a 17-probe labeled bacterial artificial chromosome contig to quantify sub-clonal populations of cells based on deletion of a single locus. Chronic lymphocytic leukemia (CLL) cells harboring deletion of the short arm of chromosome 17 (del17p), an important prognostic marker for CLL were used to demonstrate the technique. Sub-clones of del17p cells were quantified and isolated from heterogeneous CLL populations using fluorescence in situ hybridization in suspension (FISH-IS) and the locus specific probe set. Using the combination of FISH-IS with the locus-specific probe set enables automated analysis of tens of thousands of cells, accurately quantifying and isolating cells carrying a del17p. Based on the fluorescence intensity of 17p probes, 17p (TP53) deleted cells were identified and sorted using flow cytometric techniques, and enrichment was demonstrated using single nucleotide polymorphism analysis. The ability to separate sub-clones of cells based on genetic heterogeneity, independent of the clone size, highlights the potential application of this method not only in the diagnostic and prognostic setting, but also as an unbiased approach to enable further detailed genetic analysis of the sub-clone with deep sequencing approaches. © 2017 International Society for Advancement of Cytometry.

Detection of DNA fusion junctions for BCR-ABL translocations by Anchored ChromPET

Anchored ChromPET, a technique to capture and interrogate targeted sequences in the genome, has been developed to identify chromosomal aberrations and define breakpoints. Using this method, we could define the BCR-ABL1 translocation DNA breakpoint to a base-pair resolution in Philadelphia chromosome-positive samples. This DNA-based method is highly sensitive and can detect the fusion junction using samples from which it is hard to obtain RNA or cells where the RNA expression has been silenced.

Fluorescence in situ hybridization (FISH) for genomic investigations in rat

This chapter concentrates on the use of fluorescence in situ hybridization (FISH) for genomic investigations in the laboratory rat (Rattus norvegicus). The selection of protocols included in the chapter has been inspired by a comprehensive range of previously published molecular cytogenetic studies on this model organism, reporting examples of how FISH can be applied for diverse investigative purposes, varying from comparative gene mapping to studies of chromosome structure and genome evolution, to characterization of chromosomes aberrations as well as transgenic insertions. The protocols, which include techniques for the preparation of mitotic chromosomes and DNA fibers from short-term cell cultures, have been gathered through the years and repeatedly tested in our laboratory, and all together aim at providing sufficient experimental versatility to cover a broad range of cytogenetic and cytogenomic applications.

Microdissection and chromosome painting of X and B chromosomes in Locusta migratoria

Acquisition of knowledge of the nature and DNA content of B chromosomes has been triggered by a collection of molecular techniques, one of which, microdissection, has provided interesting results in a number of B chromosome systems. Here we provide the first data on the molecular composition of B chromosomes in Locusta migratoria, after microdissection of the B and X chromosomes, DNA amplification by one (B) or two (X) different methods, and chromosome painting. The results showed that B chromosomes share at least two types of repetitive DNA sequences with the A chromosomes, suggesting that Bs in this species most likely arose intraspecifically. One of these repetitive DNAs is located on the heterochromatic distal half of the B chromosome and in the pericentromeric regions of about half of the A chromosomes, including the X. The other type of repetitive DNA is located interspersedly over the non-centromeric euchromatic regions of all A chromosomes and in an interstitial part of the proximal euchromatic half of the B chromosome. Chromosome painting, however, did not provide results sufficiently reliable to determine, in this species, which A chromosome gave rise to the B; this might be done by detailed analysis of the microdissected DNA sequences.