2023 ACMG Annual Clinical Genetics Meeting Digital Edition: Poster Gallery-Overcoming Polymer-Induced Variation in Fragile X and Huntington Disease Repeat Expansion Assays

Pdf Summary

This article discusses the challenges faced in accurately quantifying trinucleotide repeats in genetic disorders such as Fragile X and Huntington Disease. The study focuses on the variability in fragment migration during the analysis process and its impact on repeat size determination. The researchers compared three methods for quantification: pre-determined bin panels, a dedicated software for Fragile X (FX) analysis, and a universal Repeat Expansion Analysis (REA) tool. <br /><br />Their analysis found that the use of POP-7 polymer as a separation medium increased the variability in fragment migration, resulting in variable repeat size determinations between runs for control samples. The use of pre-determined bin panels resulted in a high mis-call rate for both FX and HD data, particularly for certain repeat sizes. The dedicated software tool for FX analysis also resulted in a high mis-call rate, particularly for smaller repeat sizes.<br /><br />However, the REA tool, which used internal calibration for each run, provided the greatest consistency in repeat size calling across multiple runs over a 5-month period. The use of dynamic factors for calibration reduced the mis-call rate to 0% for both FX and HD assays. Overall, the researchers concluded that the REA tool compensated for the variability in fragment mobility and provided consistent repeat size quantification.<br /><br />In summary, this study highlights the challenges in accurately quantifying trinucleotide repeats in genetic disorders and the effectiveness of the REA tool in overcoming these challenges. The tool's use of internal calibration and dynamic factors resulted in consistent repeat size determination across multiple runs. This research has important implications for the diagnosis and screening of genetic disorders with trinucleotide repeat expansions.

Asset Subtitle

Presenting Author - Noel S. Reading, PhD; Co-Author - Mohamed Jama, MS; Co-Author - Pinar Bayrak-Toydemir, MD, PhD; Co-Author - Hunter Best, Ph.D.; Co-Author - Eric Frederickson, PhD; Co-Author - Makenzie L. Fulmer, PhD; Co-Author - Rong Mao, MD; Co-Author - Sherin Shaaban, MD PhD, FACMG; Co-Author - Yuan Ji, PhD, MBA, FACMG;

Meta Tag

Chromosomal Abnormalities

Chromosome Structure/Function

Genetic Testing

Methodology

Triplet and Other Repeats

Co-Author Mohamed Jama, MS

Co-Author Pinar Bayrak-Toydemir, MD, PhD

Co-Author Hunter Best, Ph.D.

Co-Author Eric Frederickson, PhD

Co-Author Makenzie L. Fulmer, PhD

Co-Author Rong Mao, MD

Co-Author Sherin Shaaban, MD PhD, FACMG

Co-Author Yuan Ji, PhD, MBA, FACMG

Presenting Author Noel S. Reading, PhD

Keywords

trinucleotide repeats

genetic disorders

Fragile X

Huntington Disease

fragment migration

repeat size determination

quantification methods

mis-call rate

internal calibration

dynamic factors