Full length htt is expressed under the control of its endogenous regulatory region. The 22.7kb minigene consists of a 14.9kb genomic fragment containing 5' regulatory sequences together with the first ten introns and exons, followed by a 6.6kb cDNA fragment that contains from exon 10 to exon 29, followed by a 1.2kb genomic fragment containing the exon 29 and the remaining polyA sites and untranscribed region at the 3' end of the gene.