PTCH2 and meningioma: Our comparison of two subgroups of NF2 meningiomas revealed that NF2-2 tumors with chr1p loss have a much lower expression of tumor suppressor PTCH2 compared to NF2-1 tumors with intact chr1p (Figure 2E), suggesting that a decreased expression of this gene may underlie a more aggressive nature of aggressive meningiomas with significant chromosomal losses, including chr22q and chr1p.