Although decreased abundance of myelin protein, proteolipid protein (PLP), attributed to loss of occupancy of a transcription activator, Yin Yang 1 (YY1) on its promoter, contributes at least in part to the myelin phenotype in ADLD, the possibility that an independent degenerative process of myelin also contributes to the phenotype has not been excluded. The gene discussed is YY1; the disease is adult-onset autosomal dominant demyelinating leukodystrophy.