TTYH1 and oligodendroglioma: Hence, molecular factors localized on chromosomal arms 1p and 19q, which are co-deleted in oligodendroglioma, involve genes encoding TTYH1 that drives invasive TM, as well as those encoding the neurotrophic factors nerve growth factor and neurotrophin 4, which increase expression of GAP43, a master regulator of TM formation.