|Number of repeats||Counts (alleles)||Percentage|
Overview of repeats
Myotonic dystrophy type 2 (DM2) is disease similar to DM1 but it is caused by tetranucleotide CCTG expansions in the intron 1 of CNBP gene (also known as ZNF9) which can even reach to 11000 copies of the repeat (Liquori et al., 2001). In most individuals the repeat tract contains (CCTG)n repeats which are interrupted by TCTG, GCTG and ACTG motifs. Uninterrupted alleles have shown to be significantly more unstable than interrupted (Bachinski et al., 2009) and instability has been correlated with the length of uninterrupted tracts. The cut-off between stable and unstable uninterrupted alleles is approximately 30 CCTG repeats (Radvanszky et al., 2013) and the premutation range is up to approximately 54 repeats (Radvanszky et al., 2013), as the smallest disease-causing allele has found to be 55 repeats of CCTG long (Bachinski et al., 2009).