FIGURE 1.

High prevalence of Alu-derived repeats in SMN locus. (A) Genomic overview of the duplicated genomic region in chromosome 5 encompassing the SMN genes. Upper panel indicates the location of genes and the three most prevalent types of repeats: SINEs, LINEs, and long terminal repeats (LTRs). Lower panel pie charts indicate the total percentage of sequence occupied by different types of repeats in either the whole SMN locus including other duplicated genes (left) or in the SMN gene itself (right). (B) Detailed view of the SMN gene and nearby surrounding sequences. SMN exons are indicated with colored boxes. Repeat sequences are indicated as colored arrows, with the direction of the arrow indicating the orientation of the repeat-derived sequence. An Alu-mediated recombination event which resulted in a deletion in an SMA patient (Wirth et al., 1999) is indicated. Two boxed regions indicate the location of known antisense transcripts derived from the SMN locus (d’Ydewalle et al., 2017; Woo et al., 2017).