Xcelom Limited (Global)
Long-Read Sequencing
Massive Tandem Repeat Panel (dmTGS)
Pioneers in Reaching Repeat Expansion Disorders
LRS Opens New Frontiers in Repeat Expansion Disorders
Advances in LRS have revolutionized the discovery of repeat expansion disorders. Nearly half of these disorders were discovered in the last decade, overcoming the limitations of older methods.
​
Apart from NGS (short-read lengths and GC bias) or limited routine PCR assays, LRS offers a clear advantage. It generates reads that span entire repeat regions. This allows for precise, simultaneous detection of repeat counts, unit sizes, and sequence interruptions for a group of genes in a single test.
Figure from reference¹
dmTGS: A Comprehensive Tandem Repeat Panel
Diagnosing tandem repeat disorders is clinically challenging due to high phenotypic variability, often requiring molecular testing to aid in diagnosis. The dmTGS test provides a precise molecular solution using SMRT sequencing technology.
Covers 68 disorders associated with 63 genes in one assay
Replaces multiple single-gene/panel tests, significantly shortening the diagnostic time
Ideal for undiagnosed cases of ataxia, neuromuscular and neurodevelopmental disorders
Features
High-Resolution Repeat Sizing
Precisely sizes repeat units with single-repeat accuracy, helping distinguish pathogenic from non-pathogenic alleles and reduce uncertainty in borderline cases with greater confidence than RP-PCR, AL-PCR, or Sanger sequencing².
Reduced Risk of False Results
Long-read length directly spans repeat regions, minimizing errors caused by primer-binding site variants, interruptions, or assay dropouts
Sensitive Mosaicism Detection
Detects low-level mosaicism, including FMR1 CGG premutations at 1% and full mutations at 5%², outperforming conventional methods
Interruption Motif Detection
Identifies repeat interruptions that affect genetic stability, inheritance risk, and disease severity
Characterization of Polymorphic Sequences
Unlike Nanopore sequencing (higher error rates) or PCR-based methods (limited by size), dmTGS can resolve complex VNTRs spanning dozens of kilobases such as 99-mer VNTRs in PLIN4²
Technology Comparison: dmTGS vs. PCR and NGS
Items
PCR methods
Southern Blot
NGS
dmTGS
Repeat count accuracy
Low
Limited to count
Limited to length <150bp
High
Gene per assay
1
1-10
10-30
63
(Most up to date)
Large repeat units (VNTR)
✔
✕
✕
✔
Interruptive motifs
✕
✕
✕
✔
Extrene GC
✔
✔
✕
✔
Send-out Testing
When considering our send-out sequencing services:
-
Consultation: Contact our team for the most current test specifications.
-
Sample Preparation: Check sample types and shipment requirements to ensure high-quality results. Please check your local export regulations and logistics partners.
-
Submission: Contact Xcelom when placing an order. Include the completed Test Request and Consent Form, along with any required documents.
Sample Requirements
Peripheral Blood: 2 mL in EDTA tube
Long-fragment gDNA
Transport Conditions
2-8℃, arrive within 72 hours
Dry ice transportation, arrive within 5 calendar days
Testing Scope
Detection of abnormal repeat numbers across 63 genes associated with 68 diseases
Turnaround Time (TAT)
29 working days
End-to-End Technology Transfer
Berry Genomics and Xcelom provide dedicated turnkey solution to bring this capability into your laboratory. We offer end-to-end support, including:
-
Lab Setup: Consultation on workflow, equipment, and kits
-
Training: Comprehensive wet-lab training for your staff
-
Bioinformatics Support: Our tailored software solutions streamline variant annotation and interpretation, automatically integrating public databases to assist with ACMG analysis
References:
1. Depienne C, Mandel JL. 30 years of repeat expansion disorders: What have we learned and what are the remaining challenges?. Am J Hum Genet. 2021;108(5):764-785.
2. Yang K, Liu Y, Zhang J, et al. dmTGS: Precise Targeted Enrichment Long-Read Sequencing Panel for Tandem Repeat Detection. Clin Chem. 2025;71(2):319-331.