PTPRT c.4090dup (D1364Gfs*24) identified in family cc765
Whole-exome sequencing in two affected members and one cancer-free relative of family cc765 (II:5, II:6 and II:7, Figure 1A) revealed a germline PTPRT frameshift mutation that was shared by the affected and absent in the unaffected relative. This family fulfilled the Amsterdam II criteria, with 5 members diagnosed of different cancer types in two successive generations (3 CRCs, 1 endometrial and 1 breast cancer), the earliest age of onset being 28 years old (Figure 1A and Supplementary Table S3). The identified variant was NM_133170.4: c.4090dup, p.(Asp1364GlyfsTer24), which will be from here on abbreviated as D1364Gfs*24. This variant is not reported in any of the public databases (gnomAD, ExAc, 1000 Genomes) and affects all of PTPRTlong protein-coding transcripts, causing the loss of the N-terminal end of the protein.