Mutations in one of 8 genes involved in telomere biology--DKC1, TINF2, TERC, TERT (telomerase reverse transcriptase), NHP2 [NHP2 ribonucleoprotein homolog (yeast)], NOP10 [NOP10 ribonucleoprotein homolog (yeast)], WRAP53 (WD repeat containing, antisense to TP53; formerly TCAB1), and CTC1 (CTS telomere maintenance complex component 1)--can be identified in approximately 50% of patients with clinical features of classic DC, the remainder being as yet uncharacterized (3, 4).
These mutations all participate in telomere maintenance but fall into 3 distinct telomere-maintenance pathways: the telomerase complex, which elongates telomeres in stem cells [disease genes TERC, TERT, DKC1, NOP10, NHP2, and WRAP53 (formerly TCAB1)]; the shelterin complex, which protects telomere ends and regulates telomerase recruitment (disease gene TINF2); and the CTS complex, which participates in telomere replication and regulates telomerase activity at the telomere end (disease gene CTC1) (1).