Since the genes of neurotrophic factors such as NGF and NT-4 (also called NTF4) that play a crucial role in the expression of GAP-43 and TTYH1 are demonstrated to be located on both chromosomal parts 1p and 19q, 1p/19q co-deleted gliomas may lack TMs due to downregulation of GAP-43 and their corresponding receptors (TrkA, TrkB), making them more susceptible to various therapies. The gene discussed is TTYH1; the disease is glioma.