For example, a recent study indicated that arginine-glutamic acid dipeptide repeats gene (RERE) is the source of the majority of the downregulated circRNAs in HD, and mutation of this gene can cause brain development (Ferguson et al., 2022), or the circHTT (2–6), a circRNA from the HTT gene that includes exons 2, 3, 4, 5, and 6, is more prevalent in the brains of HD patients than in healthy controls and has a strong positive correlation with CAG repeat length (Ayyildiz et al., 2023). The gene discussed is RERE; the disease is Huntington disease.