SNOMEDCT: 719300001; ORPHA: 276193; DO: 0050982;
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
Gene/Locus |
Gene/Locus MIM number |
|---|---|---|---|---|---|---|
| 20p13 | Spinocerebellar ataxia 35 | 613908 | Autosomal dominant | 3 | TGM6 | 613900 |
A number sign (#) is used with this entry because of evidence that autosomal dominant spinocerebellar ataxia-35 (SCA35) is caused by heterozygous mutation in the TGM6 gene (613900) on chromosome 20p13.
Spinocerebellar ataxia-35 (SCA35) is an autosomal dominant adult-onset neurologic disorder characterized by difficulty walking due to cerebellar ataxia. The age at onset ranges from teenage years to late adulthood, and the disorder is slowly progressive. Additional features may include hand tremor, dysarthria, hyperreflexia, and saccadic eye movements (summary by Guo et al., 2014).
For a general discussion of autosomal dominant spinocerebellar ataxia, see SCA1 (164400).
Wang et al. (2010) reported a 4-generation Chinese family in which 9 individuals developed spinocerebellar ataxia with a mean age at onset of 43.9 years (range, 40 to 48 years). Early features included walking difficulty, ataxia, and cerebellar dysarthria, while upper limb involvement with incoordination occurred later. There was slow progression, and most needed a walking aid or became wheelchair-dependent after about 10 years. Additional features included tremor, hyperreflexia, extensor plantar responses, torticollis, ocular dysmetria, and position sense defects. None of the patients had nystagmus, ophthalmoplegia, peripheral neuropathy, or cognitive decline. Two sisters from a second unrelated Chinese family had a similar disorder.
Li et al. (2013) reported a 3-generation Chinese family in which 7 individuals had spinocerebellar ataxia. The proband was a 53-year-old woman who reported unsteady gait and frequent falls since her early teenage years. As an adult, she showed cerebellar ataxia with intention tremor and dysmetria, and pyramidal signs with hyperreflexia and extensor plantar responses. She used crutches for walking. Her deceased father was apparently affected, and she had 2 similarly affected sisters, one of whom was wheelchair-bound. Her son, who was also affected, had mild mental retardation with delayed speech. The disorder was slowly progressive.
Guo et al. (2014) reported 4 patients from 3 Han Chinese families with SCA35. Clinical features included limb ataxia, gait ataxia, hyperreflexia, dysarthria, hand tremor, and saccadic pursuit. The age at onset was highly variable, ranging from 15 to 56 years, and the disorder was slowly progressive. One patient had cognitive decline. Brain imaging showed cerebellar atrophy.
The transmission pattern of SCA35 in the families reported by Wang et al. (2010) was consistent with autosomal dominant inheritance.
By genomewide linkage analysis of a large Chinese family with autosomal dominant SCA, Wang et al. (2010) identified an 8.5-Mb locus on chromosome 20p13-p12.2 (maximum 2-point lod score of 5.36 at D20S437).
By exome sequencing in affected members of a large Chinese family with SCA35, Wang et al. (2010) identified a heterozygous mutation in the TGM6 gene (L517W; 613900.0001). A second unrelated Chinese family with SCA35 was found to carry a different heterozygous mutation in the TGM6 gene (D327G; 613900.0002).
By exome sequencing, Li et al. (2013) identified a heterozygous mutation in the TGM6 gene (D510H; 613900.0003) in affected members of a Chinese family with SCA35.
In affected members of 3 Han Chinese families with SCA35, Guo et al. (2014) identified 3 different heterozygous mutations in the TGM6 gene (613900.0003-613900.0005). In vitro functional expression studies in HEK293 cells showed that the mutant proteins were unstable and had decreased activity compared to wildtype. The 3 families with SCA35 accounted for 0.6% of 512 Han Chinese families with SCA who underwent genetic analysis.
Guo, Y.-C., Lin, J.-J., Liao, Y.-C., Tsai, P.-C., Lee, Y.-C., Soong, B.-W. Spinocerebellar ataxia 35: novel mutations in TGM6 with clinical and genetic characterization. Neurology 83: 1554-1561, 2014. [PubMed: 25253745] [Full Text: https://doi.org/10.1212/WNL.0000000000000909]
Li, M., Pang, S. Y. Y., Song, Y., Kung, M. H. W., Ho, S.-L., Sham, P.-C. Whole exome sequencing identifies a novel mutation in the transglutaminase 6 gene for spinocerebellar ataxia in a Chinese family. Clin. Genet. 83: 269-273, 2013. [PubMed: 22554020] [Full Text: https://doi.org/10.1111/j.1399-0004.2012.01895.x]
Wang, J. L., Yang, X., Xia, K., Hu, Z. M., Weng, L., Jin, X., Jiang, H., Zhang, P., Shen, L., Guo, J. F., Li, N., Li, Y. R., and 9 others. TGM6 identified as a novel causative gene of spinocerebellar ataxias using exome sequencing. Brain 133: 3510-3518, 2010. [PubMed: 21106500] [Full Text: https://doi.org/10.1093/brain/awq323]