Table 2.

Common molecular features observed in expansion diseases.

Disease	Gene	Expansion	Repeat location	RAN translation-toxicity	RAN translation	RNA toxicity	Loss of function
Friedreich’s ataxia	FRDA	GAA/TTC 55–200	Intron	No	N/A	No	Downregulation of frataxin
Myotonic Dystrophy type 1	DMPK	CTG/CAG 50–1000	3’UTR	No	Sense [poly(C), poly(A), poly(L)] Antisense [poly(Q), poly(A), poly(S)]	Yes Recruitment of MBNL1 into RNA foci	Downregulation of MBNL1 and DMPK
Myotonic Dystrophy type 2	CNBP/ZNF9	CCTG/CAGG 55–11000	Intron 1	Yes	Sense [poly(LPAC)] Antisense [poly(QAGR)]	Yes Disbalance of MBNL1 and CUGBP1 and recruitment of MBNL1 into RNA foci	Downregulation of CNBP
C9orf72	C9orf72	GGGGCC/ GGCCCC 100–4500	Intron 1	Yes	Sense [poly (GP), poly(GA), poly (GR)] Antisense [poly (GP), poly (PA), poly (PR)]	Yes Recruitment of RNA binding proteins (hnRNP-H) into RNA foci	Downregulation of C9orf72