Moreover, in some SCAs, both the abnormal repeat expansions and single nucleotide variants appear to cause ataxia-like symptoms (e.g., SCA6) with both gain of function and loss of function mechanisms underlying the observed phenotypes, emphasizing the complexity of SCAs etiology (Pietrobon 2002; Indelicato and Boesch 2021). Here, CACNA1A is linked to cerebellar ataxia.