However, efforts to model hamartomas have largely been unsuccessful, in part due to the early lethality of homozygous germline mutations in Pten (Di Cristofano et al., 1998) and other hamartoma-associated genes, such as tuberous sclerosis genes (Tsc1/Tsc2) (Kobayashi et al., 1999, 2001). The gene discussed is TSC1; the disease is hamartoma.