TK2 and spinocerebellar ataxia type 31: In the BEAN1 direction, the penta-nucleotide repeat sequence has the configuration 5ʹ-(TGGAA)n(TAGAA)n(TAAAATAGAA)n-3ʹ, whereas in the TK2 direction, the sequence is 5ʹ-(TTCTATTTTA)n(TTCTA)n(TTCCA)n-3ʹ, so that two complimentary RNA sequences are independently expressed: (UGGAA)n(UAGAA)n(UAAAAUAGAA)n from BEAN1 and (UUCUAUUUUA)n(UUCUA)n(UUCCA)n from TK2. There is no doubt that the penta-nucleotide repeat is the direct cause of SCA31, as the length of the repeat inversely correlates with the age of onset [1].