Analysis of human invasive cytotrophoblasts using multicolor fluorescence in situ hybridization

Full Karyotype Interphase Cell Analysis

Aneuploidy seems to play not only a decisive role in embryonal development but also in tumorigenesis where chromosomal and genomic instability reflect a universal feature of malignant tumors. The cost of whole genome sequencing has fallen significantly, but it is still prohibitive for many institutions and clinical settings. No applied, cost-effective, and efficient technique has been introduced yet aiming at research to assess the ploidy status of all 24 different human chromosomes in interphases simultaneously, especially in single cells. Here, we present the selection of human probe DNA and a technique using multistep fluorescence in situ hybridization (FISH) employing four sets of six labeled FISH probes able to delineate all 24 human chromosomes in interphase cells. This full karyotype analysis approach will provide additional diagnostic potential for single cell analysis. The use of spectral imaging (SIm) has enabled the use of up to eight different fluorochrome labels simultaneously. Thus, scoring can be easily assessed by visual inspection, because SIm permits computer-assigned and distinguishable pseudo-colors to each probe during image processing. This enables full karyotype analysis by FISH of single-cell interphase nuclei.

Identification of sesame (Sesamum indicum L.) chromosomes using the BAC-FISH system

Sesame (Sesamum indicum L.; Pedaliaceae) is a commercially valuable oilseed crop with high oil content. Its small genome size favours the genomic analysis of key biological processes, such as oil synthesis and metabolism. However, the 13 chromosome pairs of sesame have not been characterised because of technological limitations and their small size. We constructed a BAC library comprising 57,600 BAC clones for sesame. The estimated genome coverage of the sesame BAC library was 13.8×. The successive double colour fluorescence in situ hybridisation (FISH) with bacterial artificial chromosomes (BACs) for sesame was established in this study. Subsequently, the 13 sesame chromosome pairs were individually differentiated using 17 specific BACs for the first time. The schematic of the sesame chromosome set was drawn according to the chromosome relative length and relative position of the BAC signal. The cytogenetic characteristics of sesame chromosomes were also explored. The results provide the technical background required for further cytogenetic map construction, genome assembly and localisation of the DNA sequence in sesame.

High Performance DNA Probes for Perinatal Detection of Numerical Chromosome Aberrations

Human reproduction is a tightly controlled process of stepwise evolution with multiple, mostly yet unknown milestones and checkpoints. Healthy halpoid gametes have to be produced by the parents, which will fuse to form the diploid zygote that implants in the female uterus and grows to become first an embryo, then a fetus and finally matures into a newborn. There are several known risk factors that interfere with normal production of gametes, spermatocytes or oocytes, and often cause embryonic mortality and fetal demise at an early stage. Yet some embryos with chomosomal abnormalities can develop beyond the critical first trimester of pregnancy and, while those with supernumary chromosomes in their hyperdiploid cells will be spontaneously aborted, a small fraction of fetuses with an extra chromosome continues to grow to term and will be delivered as a liveborn baby. While minor clinical symptoms displayed by children with trisomies are manageable for many parents, the burden of caring for a child with numerical chromosome abnormalities can be overwhelming to partners or individual families. It also poses a significant financial burden to the society and poses ethical dilemma. In this communication, we will review the progress that has been made in the development of molecular techniques to test individual fetal cells for chromosomal imbalances. We will focus our discussion on the direct visualization of chromosome-specific DNA sequences in live or fixed specimens using fluorescence in situ hybridization (FISH) and, more specifically, talk about the groundbreaking progress that in recent years has been achieved towards an improved diagnosis with novel, chromosome-specific DNA probes.