MAPT and Alzheimer disease: In contrast, a widespread loss of heterochromatin containing H3K9me2 and HP1 has been observed in the head of tau transgenic Drosophila and in motor neurons of tau transgenic mice and in the hippocampal neurons of patients with AD.199 In Drosophila tauopathy models, wild-type and mutated tau reduced H3K9me2, upregulating the expression of genes such as Nvd, Ir41a, and Ago3 that are normally silenced or expressed at low levels in fly.