TSC1 and tuberous sclerosis: TSC affects approximately 1 in 10,000 individuals and is caused by inactivating mutations in either TSC1 on chromosome 9q34 (MIM# 605284; van Slegtenhorst et al., 1997), or TSC2 on chromosome 16p13.3 (MIM# 191092; European Chromosome 16 Tuberous Sclerosis Consortium, 1993).