Moreover, co-expression network analysis revealed that developmental genes are co-expressed with HTT in the occipital cortex, a region undergoing the greatest rate of cortical atrophy in HD during motor conversion.15 These findings suggest that lower wtHTT expression in HD expansion carriers during development, due to the presence of a single wild-type allele, may render specific areas vulnerable to neurodegeneration in adulthood. The gene discussed is HTT; the disease is Huntington disease.