. 2002 May;4(2):108–113. doi: 10.1016/S1525-1578(10)60689-7

Table 1.

Molecular Basis of Five Spinocerebellar Ataxia Disorders

Disease	Gene	Protein	Number of CAG repeats			Selected reference
Disease	Gene	Protein	Normal	Intermediate^*	Abnormal	Selected reference
SCA1	SCA1	Ataxin 1	≤36	37–44	44–83	17, 18
SCA2	SCA2	Ataxin 2	≤31	30–34	35–∼400	19
SCA3	MJD	SCA3/MJD1	≤47	53, 54	55–86	20, 21
SCA6	CACNAIA	α1 Voltage-gated calcium channel	≤20	20?	21–33	22, 24
SCA7	SCA7	Ataxin 7	≤19	28–35	36–>300	16, 23

Intermediate is used here to define two categories of alleles: those that are normal but may expand into the abnormal range upon transmission and those that show reduced penetrance. For simplicity, the table does not detail the rare alleles at the borders of the categories that are difficult to assign as normal, intermediate, or abnormal.

CAG repeats expand into the hundreds in rare neonatal/juvenile onset cases of SCA2 and SCA7. 25 26