A novel mutation identified within the DICER1 RNase IIIb domain in a single seminoma sample. Amino acid numbering is based on DICER1 reference sequence [GenBank:NM_177438]. 2A. The aberrant HRM curve corresponding to the DICER1 mutation. The curves on the baseline represent samples without a sequence variant (this was confirmed with Sanger sequencing in one sample). 2B. A Sanger sequencing trace from the sample that showed the aberrant HRM curve in 2A. The heterozygous sequence variant is indicated by an arrow. This mutation is predicted to change an Arginine to a Glutamine at position 1725 of DICER1. 2C. The RNase IIIb domain in DICER1, containing amino acids 1666–1824. The location of the mutation (R1725Q) identified in this study is shown by the red bar. The locations of the four metal-binding residues (all acidic amino acids) frequently mutated in Sertoli-Leydig cell tumours are shown by black bars. The region of 100% conservation across at least 42 species at the amino acid level (residues 1705–1741) is indicated by the horizontal black bar.