HTT and hereditary pheochromocytoma-paraganglioma: We used neuronal (PC12) cell lines derived from rat pheochromocytoma that express an inducible enhanced green fluorescent protein (EGFP)-tagged HTT exon 1 fragment with 23 (HD-Q23) or 74 (HD-Q74) glutamine repeats that shape the non-mutant and mutant form of HTT, respectively [18].