Table 2: List of polyglutamine (CAG-expansion) diseases.

DiseaseSites of neuropathologyCAG triplet numberGene product (Intracellular localization of protein deposits)Reference
NormalDisease

Corea major or Huntington’s disease (HD)Striatum (medium spiny neurons) and cortex in late stage6–3536–121Huntingtin(n, c)[49]

Spinocerebellar Ataxia Type 1 (SCA1)Cerebellar cortex (Purkinje cells), dentate nucleus, and brainstem6–3940–81Ataxin-1 (n, c)[50]

Spinocerebellar Ataxia Type 2 (SCA2)Cerebellum, pontine nuclei, substantia nigra15–2935–64Ataxin-2 (c)[51]

Spinocerebellar Ataxia Type 3 (SCA3) or Machado-Joseph disease (MJD)Substantia nigra, globus pallidus, pontine nucleus, cerebellar cortex13–4261–84Ataxin-3 (c)[52]

Spinocerebellar Ataxia Type 6 (SCA6)Cerebellar and mild brainstem atrophy4–1821–30Calcium channel subunit (α1A) (m)[53]

Spinocerebellar Ataxia Type 7 (SCA7)Photoreceptor and bipolar cells, cerebellar cortex, brainstem7–1737–130Ataxin-7 (n)[54]

Spinocerebellar Ataxia Type 12 (SCA12)Cortical, cerebellar atrophy7–3241–78Brain-specific regulatory subunit of protein phosphatase PP2A (?)[55]

Spinocerebellar Ataxia Type 17 (SCA17)Gliosis and neuronal loss in the Purkinje cell layer29–4246–63TATA-binding protein (TBP) (n)[56]

Spinobulbar Muscular Atrophy (SBMA) or Kennedy diseaseMotor neurons (anterior horn cells, bulbar neurons) and dorsal root ganglia11–3440–62Androgen receptor (n, c)[57]

Dentatorubral-pallidoluysian atrophy (DRPLA)Globus pallidus, dentatorubral and subthalamic nucleus7–3549–88Atrophin (n, c)[58]

Cellular localization: c, cytosolic; m, transmembrane; n, nuclear.