The duplicated CDKL5 exon 3 is present in a subset of the proband’s CDKL5 transcripts
(A) RT-PCR using primers specific to exons 2–5 of CDKL5 cDNA results in a 240 bp amplicon in proband (P), dad (D), and mom (M). An additional 275 bp amplicon is present only in the proband (asterisk).
(B) Sanger sequencing of both amplicons from the proband confirmed that the 240 bp amplicon includes the normal, expected sequencing and inclusion of a duplicated exon 3 in the upper, 275 bp band. This is predicted to lead to a frameshift (red circle) and downstream stop, p.Thr35ProfsTer52. Yellow outlined box, exon 3 sequence; orange outlined box, duplicated exon 3 sequence.