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Table 1 Microsatellite repeat expansion disorders

From: RNA biology of disease-associated microsatellite repeat expansions

Disorder Repeating unit Genomic location Gene name Normal length Pathogenic length Expanded repeats result in: Repeat discovery & references
Gene silencing xtrRNA transcription xtrRNA proteins xtrRNA foci
FXS/FRAXA CGG 5’UTR FMR1 6-55 200+ Yes* No No No [114, 161, 230, 303]
SBMA CAG Coding AR 9-36 38-62 No Yes Yes* L .D. [167]
DM1 CTG 3’UTR DMPK 5-37 50-10000 No Yes* Yes Yes* [193]
HD CAG Coding HTT 10-35 35+ No Yes Yes* L.D. [192]
SCA1 CAG Coding ATXN1 6-35 49-88 No Yes Yes* L.D. [232]
FRAXE CCG 5'UTR AFF2 4-39 200-900 Yes* No No No [152]
DRPLA CAG Coding ATN1 6-35 49-88 No Yes Yes* L.D. [155]
SCA3 CAG Coding ATXN3 12-40 55-86 No Yes Yes* Yes [140]
SCA2 CAG Coding ATXN2 14-32 33-77 No Yes Yes* L.D. [127, 253]
FRDA GAA Intron FXN 8-33 90+ Yes* Yes / No No No [30]
SCA6 CAG Coding CACNA1A 4-18 21-30 No Yes Yes* L.D. [337]
Promoter CSTB 2-3 30-80 Yes* Yes / No No No [170]
SCA7 CAG Coding ATXN7 7-17 38-120 No Yes Yes* L.D. [57]
OPMD GCG Coding PABPN1 6-10 12-17 No Yes Yes* No [23]
SCA8 CTG 3’UTR ATXN8 16-34 74+ No Yes Yes* Yes* [156]
SCA12 CAG 5’UTR PPP2R2B 7-28 66-78 No Yes* No No [121]
SCA10 ATTCT Intron ATXN10 10-20 500-4500 No Yes ? Yes* [205]
SCA17 CAG Coding TBP 25-42 47-63 No Yes Yes* L.D. [224]
DM2 CCTG Intron CNBP 10-26 75-11000 No Yes ? Yes* [184]
FXTAS/FXPOI CGG 5’UTR FMR1 6-55 55-200 No Yes Yes* Yes* [143, 287]
HDL2 CTG/CAG 3'UTR/antisense JPH3 <50 50+ No Yes ? Yes* [120]
SCA31 TGGAA Intron TK2/BEAN 0 45+ No Yes Yes* Yes* [256]
SCA36 GGCCTG Intron Nop56 3-14 650+ No Yes ? Yes* [153]
C9FTD/ALS GGGGCC Intron C9ORF72 2-25 25+ No Yes Yes* Yes* [59, 248]
FRA7A CGG Intron ZFN713 5-22 85+ No Yes* / No No No [209]
FRA2A CGG Intron AFF3 8-17 300+ No Yes* / No No No [210]
  1. Disorders are listed in order of the year they were discovered, with the appropriate references relating to their discovery. This table highlights known RNA biology for each disease with respect to xtrRNA transcription, translation, and formation of nuclear focal aggregates
  2. Dagger symbol (†) indicates that athough the CAG repeat for SBMA was discovered first, the CGG repeat for FXS was published first. Asterisk (*) indicates the most likely repeat-associated disease mechanism(s) for that disorder. L.D. length-dependent, SBMA Spinal-Bulbar Muscular Atrophy, EPM1 Progressive Myoclonus Epilepsy 1 (Unverricht–Lundborg Disease), FXS/FRAXA Fragile X Syndrome, DM Myotonic Dystrophy, HD Huntington’s Disease, SCA Spinocerebellar Ataxia, FRAXE Fragile X E Syndrome, DRPLA Dentatorubral-Pallidoluysian Atrophy, FRDA Friedreich Ataxia, OPMD Oculopharyngeal Muscular Dystrophy, FXTAS Fragile X–Associated Tremor/Ataxia Syndrome, FXPOI Fragile X-Associated Primary Ovarian Insufficiency, HDL2 Huntington’s Disease-Like 2, C9FTD/ALS C9ORF72-Associated Frontotemporal Dementia and Amyotrophic Lateral Sclerosis, FRA7A CGG Expansion at Fragile Site 7A, FRA2A CGG Expansion at Fragile Site 2A