Using a second quantitative PCR method, Taqman qPCR, DMPK mRNA expression normalized to GTF2B, or to a second reference gene, Glyceraldehyde 3-phosphate dehydrogenase (GAPDH), also appeared significantly lower in urine exRNA of DM1 patients than UA subjects, and appeared similar in serum exRNA from both groups (Supplementary Fig. 3). Here, GAPDH is linked to myotonic dystrophy type 1.