Rapid prenatal diagnosis of common numerical chromosomal abnormalities by high-resolution melting analysis of segmental duplications

Clinical Utility of a High-Resolution Melting Test for Screening Numerical Chromosomal Abnormalities in Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) occurs in approximately 5% of clinically identified pregnancies. Determining the cause of RPL is essential. Genetic testing, accompanied by an evidence-based workup, is the well-accepted process for evaluating RPL; however, current genetic tests have limitations in clinical practice. We, thus, developed a high-resolution melting analysis-based test (HRM test) to screen for the most common numerical chromosomal abnormalities present in the products of conception. We examined 765 products-of-conception samples with known karyotypes retrospectively using the HRM test, which showed high technical sensitivity (96.1%) and specificity (96.3%) as well as a high positive predictive value (95.9%) for the screening of chromosomal abnormalities. The cost-effectiveness of four RPL evaluation strategies that employ different genetic tests, karyotyping, chromosomal microarray/next-generation sequencing, the HRM test, and a combination of the HRM test and chromosomal microarray/next-generation sequencing, was then compared. The costs of diagnosing an explained RPL using karyotyping or the HRM test alone were similar. Performance of the HRM screening test before chromosomal microarray/next-generation sequencing analysis improved cost-effectiveness by approximately 30%. Cost-effectiveness was more prominent in the advanced maternal age group. Thus, the HRM test could be used as an initial screening tool, followed by other diagnostic methods to improve the cost-effectiveness of RPL evaluation, or as an alternative genetic test when other methods are unavailable or unaffordable.

Rapid and simultaneous detection of common aneuploidies by quadruplex real-time polymerase chain reaction combined with melting curve analysis

BACKGROUND

During the prenatal period, the number variation of chromosomes 13, 18, 21, X and Y accounts for more than 80% of the clinically significant chromosomal abnormalities diagnosed. Rapid tests for prenatal diagnosis of these abnormalities can improve pregnancy management and alleviate parental anxiety. Here, we present a molecular alternative method for detecting common aneuploidies.

METHODS

This method is based on co-amplification of segmental duplications located on two different chromosomes using a single pair of primers. Segmental duplications have a high degree of sequence identity, but have single-nucleotide differences in some regions. These sequence differences can be quantified using melting curve analysis of dual-labeled probes to estimate the relative dosages of different chromosomes. We designed two quadruplex real-time PCR assays to detect aneuploidies of chromosomes 13, 18, 21, X and Y.

RESULTS

We examined 75 aneuploid DNA samples and 56 unaffected DNA control samples using these two assays and correctly identified all samples. Four cases of unbalanced translocation were also accurately detected. The observed averaged ratio for each chromosomal disorder was similar to the theoretically expected value.

CONCLUSIONS

Our real-time assay is a robust, rapid, and easy to conduct technique for prenatal diagnosis of common aneuploidies, representing a competitive alternative for use in diagnostic laboratories.

Combined Use of Molecular Markers and High-Resolution Melting (HRM) to Assess Chromosome Dosage in Potato Hybrids

In plants, the most widely used cytological techniques to assess parental genome contributions are based on in situ hybridization (FISH and GISH), but they are time-consuming and need specific expertise and equipment. Recent advances in genomics and molecular biology have made PCR-based markers a straightforward, affordable technique for chromosome typing. Here, we describe the development of a molecular assay that uses single-copy conserved ortholog set II (COSII)-based single nucleotide polymorphisms (SNPs) and the high-resolution melting (HRM) technique to assess the chromosome dosage of interspecific hybrids between a Solanum phureja-S. tuberosum diploid (2n = 2x = 24) hybrid and its wild relative S. commersonii. Screening and analysis of 45 COSII marker sequences allowed S. commersonii-specific SNPs to be identified for all 12 chromosomes. Combining the HRM technique with the establishment of synthetic DNA hybrids, SNP markers were successfully used to predict the expected parental chromosome ratio of 5 interspecific triploid hybrids. These results demonstrate the ability of this strategy to distinguish diverged genomes from each other, and to estimate chromosome dosage. The method could potentially be applied to any species as a tool to assess paternal to maternal ratios in the framework of a breeding program or following transformation techniques.