Rapid prenatal diagnosis of Down syndrome using quantitative fluorescence in situ hybridization on interphase nuclei

Quantitative Fluorescence In Situ Hybridization (QFISH)

Fluorescence in situ hybridization (FISH) has a wide spectrum of applications in current molecular cytogenetic and cancer research. This is a unique technique that can be used for chromosomal DNA analysis in all cell types, at all stages of the cell cycle, and at molecular resolution. Recent developments in microscopy and imaging systems have allowed quantification of digital FISH images (quantitative FISH or QFISH) and have provided a new way for molecular cytogenetic analysis at single-cell level. QFISH can be applied for studying chromosome imbalances in interphase nuclei or metaphase spreads, measuring relative DNA content at chromosomal loci and identifying parental origin of homologous chromosomes. Here, a QFISH protocol suitable for the majority of DNA probes using the popular US National Institute of Health developed ImageJ software is described.

State-of-the-art FISHing: automated analysis of cytogenetic aberrations in interphase nuclei

Interphase fluorescence in situ hybridization (i-FISH) is a powerful tool for visualizing various molecular targets in non-dividing cells. Manual scoring of i-FISH signals is a labor intensive, time-consuming, and error-prone process liable to subjective interpretation. Automated evaluation of signal patterns provides the opportunity to overcome these difficulties. The first report on automated i-FISH analysis has been published 20 years ago and since then several applications have been introduced in the fields of oncology, and prenatal and fertility screening. In this article, we provide an insight into the automated i-FISH analysis including its course, brief history, clinical applications, and advantages and challenges. The lack of guidelines for describing new automated i-FISH methods hampers the precise comparison of performance of various applications published, thus, we make a proposal for a panel of parameters essential to introduce and standardize new applications and reproduce previously described technologies.

Automated scoring of multiprobe FISH in human spermatozoa

In the case of chromosomal aneuploidy in sperm wherein the incident rate is low and a large number of cells require scoring, automated methods that rely on computer software to segment and to count fluorescence signals are particularly necessary due to countless hours spent in reading slides and to the potential for interoperator differences. The purpose of this pilot experiment was to determine whether there were significant differences in the estimates of disomy frequency produced by automated versus manual scoring of signals for chromosome X, Y, and 18 in human sperm. The frequency of X18, Y18, XX18, YY18, and XY18 were determined in four separate normozoospermic samples. Slides were hybridized using a standard sperm FISH protocol for centromere-specific probes. Between 500 and 564, DAPI positive nuclei were captured from each sample and scored using the automated system, and the same slides were scored by a trained cytogeneticist, who was blind to the purpose of the study and the automated system results. None of the estimated frequencies was significantly different between manual and automated methods, regardless of whether individual slides or pooled results across all samples were compared. To our knowledge, this is the first report examining the validity of automated cell scoring in human spermatozoa. The results from this pilot exploration of sperm FISH suggest the comparability between automated and manual methods for estimating sex chromosome disomy and provide evidence that automated laser scanning of multiprobe sperm FISH should be explored further.

FastFISH: technique for ultrarapid fluorescence in situ hybridization on uncultured amniocytes yielding results within 2 h of amniocentesis

Rapid aneuploidy detection methods allow prenatal diagnosis results to be released within 48 h, but not on the same day as the invasive test. We aimed to develop a rapid fluorescence in situ hybridization (FISH) method (FastFISH) that releases accurate results on the same day as amniocentesis. FastFISH was optimized to be completed within 2 h of sample collection using CEP and LSI probes for chromosomes 13, 18, 21, X, Y and DiGeorge syndrome (DGS). The technique was tested on 100 consecutive amniotic fluid samples in a blinded study. It was also validated as a 1-day molecular genetic test on three representative fetal tissue samples: chorionic villus, amniotic fluid and fetal blood. In the blinded study, FastFISH results were ready within 2 h of sample collection. Of the 100 amniotic fluid samples, 49 male and 50 female fetuses were identified. One fetus was 47, XXY (Klinefelter syndrome). Three fetuses had trisomy 21. One fetus suspected of DGS by ultrasound was identified as normal. Results of FastFISH analyses in all 100 cases were concordant with their karyotypes (100% accuracy; lower 95% CI, 97.05%). In the 1-day test validation, all results were released on the same day and were concordant with their respective karyotypes. FastFISH allows results to be released on the same day as amniocentesis. It represents the necessary development for a 1-day prenatal diagnosis service.

Diagnostic Molecular Pathology: An Increasingly Indispensable Tool for the Practicing Pathologist

Context.—Diagnostic molecular pathology is rapidly becoming an indispensable tool for anatomic pathologists. Familiarity with some of the technologic principles and current, as well as upcoming, molecular diagnostic applications is greatly advantageous for today's practice of pathology.

Objectives.— To provide a discussion of the most common techniques currently used in molecular pathology laboratories and review their essential applications to diagnosis and management of neoplastic diseases.

Data Sources.—A literature review and illustrative cases from the authors' molecular diagnostic practices.

Conclusions.—Applications such as clonality assays, molecular cytogenetics, and chimerism analysis are providing us with accurate tools to resolve difficult diagnostic and management decisions in hemato-oncology. This should serve as a future model to expand molecular applications into the wider field of solid tumors.

A novel diagnostic strategy for trisomy 21 using short tandem repeats

Molecular technique with STRs can rapidly diagnose aneuploidy. In order to improve its fidelity, we developed a novel STR-based strategy for fast diagnosis of trisomy 21 and constructed a multimarker diagnostic system according to it. The system is based on nine STRs, of which two were previously known and seven were newly identified from the genomic sequence of the long arm of chromosome 21. They were confirmed to be highly polymorphic in the Chinese population by PCR amplification and gel electrophoresis. The combination of nine STR markers, when applied to DNA from 102 Chinese individuals with normal karyotype, did not yield any false-positives, and clearly revealed three different alleles in DNA from 15 out of 18 trisomy 21 patients. The results show that our new strategy can provide an alternative molecular technique for the rapid detection of aneuploidy.