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Overview

Expansions of short tandem repeats (STRs) are detected by ExpansionHunter (v5) as part of the DRAGEN software. STRs are detected only at loci defined in PanelApp STRs.

STR expansions are only reported in affected participants. All repeat expansion VCF files are available to download, containing all loci analysed.

An up-to-date list and information about specific STR loci and the associated gene panels can be found in PanelApp.

Note

Some STR loci are green on some panels, and red on others.

Only STR loci that are green on a panel applied in the analysis and that follow the relevant mode of inheritance will be reported.

Information found in PanelApp relates to the following STR loci:

  • AR
  • ATN1
  • ATXN1
  • ATXN2
  • ATXN3
  • ATXN7
  • ATXN10
  • CACNA1A
  • C9orf72
  • CSTB
  • DMPK
  • FMR1
  • FXN
  • HTT
  • JPH3
  • NOP56
  • PPP2R2B
  • TBP

Information for each STR includes:

  • the genomic coordinates of the repeat analysed (both GRCh37 and GRCh38 assemblies)
  • the repeat motif or sequence (e.g. CAG)
  • the normal and pathogenic number of repeats associated with each locus.

The internal repeat thresholds have been reviewed and agreed by NHS clinical experts, and are an essential aspect of STR tiering.