Alternative titles; symbols
SNOMEDCT: 719251009; ORPHA: 98772; DO: 0050970;
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
Gene/Locus |
Gene/Locus MIM number |
|---|---|---|---|---|---|---|
| 1p13.2 | Spinocerebellar ataxia 19 | 607346 | Autosomal dominant | 3 | KCND3 | 605411 |
A number sign (#) is used with this entry because autosomal dominant spinocerebellar ataxia-19 (SCA19), also known as SCA22, is caused by heterozygous mutation in the KCND3 gene (605411) on chromosome 1p13.
Spinocerebellar ataxia-19 (SCA19) is an autosomal dominant disorder characterized by progressive cerebellar ataxia with a variable age of onset (age 2 years to late adulthood). Other neurologic manifestations include developmental delay and cognitive impairment; movement disorders including myoclonus, dystonia, rigidity, and bradykinesia; and seizures.
For a general discussion of autosomal dominant spinocerebellar ataxia, see SCA1 (164400).
Schelhaas et al. (2001) reported a 4-generation Dutch family with a distinct form of autosomal dominant cerebellar ataxia (ADCA) type I. Affected members showed a relatively mild ataxia syndrome with cognitive impairment, poor performance on the Wisconsin Card Sorting Test, myoclonus, and a postural irregular tremor of low frequency. There was no indication of sex-limited transmission. Genetic loci implicated in other forms of spinocerebellar ataxia were excluded by mutation analysis or linkage studies. By neuropathologic examination, Duarri et al. (2012) found loss of Purkinje cells in the cerebellum of 1 of the patients reported by Schelhaas et al. (2001). The anterior part of the vermis was most severely affected, followed by the posterior vermis and the cerebellar hemispheres. There was also degeneration and atrophy in both the molecular and internal granular layers. Purkinje cell bodies showed intense staining for KCND3 within large puncta.
Chung et al. (2003) reported a 4-generation Han Chinese family with autosomal dominant cerebellar ataxia. The proband (in generation II) was a 68-year-old man with a 23-year history of gait and limb ataxia. He also had hyporeflexia, dysphagia, dysarthria, and gaze-evoked horizontal nystagmus. MRI showed cerebellar atrophy. Examination of 8 other affected family members revealed a mean age at onset of 40.5 years in generation II, 20.7 years in generation III, and 12.5 years in generation IV, suggesting genetic anticipation. The initial symptom in all affected members was gait ataxia, followed by trunk and limb ataxia, dysarthria, and 'cogwheel' pursuits of the eyes. No patients, including the proband who was most severely affected, showed cogwheel rigidity, myoclonus, tremor, akinesia, sensory deficits, seizures, or cognitive impairment. Chung et al. (2003) noted that the lack of additional signs in these patients indicated a pure form of ADCA that is best classified as ADCA III. Lee et al. (2012) reported follow-up of the Han Chinese family reported by Chung et al. (2003), which had 13 affected individuals. The age at onset ranged from 13 to 46 years. All had a slowly progressive form of cerebellar ataxia with mild oculomotor abnormalities, such as nystagmus and saccadic pursuits, dysarthria, and decreased reflexes in the lower limbs. Three patients showed mild cerebellar atrophy on brain MRI.
Lee et al. (2012) reported a French family in which 8 individuals presented with slowly progressive cerebellar ataxia with onset between 24 and 51 years. Additional variable features included impaired vibration sense at the ankles (3 patients), hyperreflexia (3), mild cogwheel rigidity (2) urinary urgency or incontinence (5), and eye movement abnormalities (6). Six patients had cerebellar atrophy on brain imaging. Only 1 patient was wheelchair-bound after 43 years of disease.
Smets et al. (2015) reported a Belgian boy with SCA19 with a more severe and complex phenotype. At 3 years of age, he was noted to have slowing of motor milestones with a progressive broad-based gait, staccato speech, and intellectual disability. At age 5 years, he had frequent nocturnal muscle jerks and episodes of staring and problems with concentration. He was diagnosed with attention deficit-hyperactivity disorder, which was unresponsive to methylphenidate. EEG showed frequent paroxysmal rhythmic theta waves in the frontal and parietal regions, and a diagnosis of epilepsy was made; seizures were responsive to valproate. At age 10 years, he was noted to have severe cerebellar ataxic gait, severe cerebellar limb ataxia, cerebellar dysarthria, and saccadic eye movements. On neuropsychologic testing, his total IQ was 54. Brain MRIs performed at ages 6 and 10 were normal.
Huin et al. (2017) reported 16 patients in 2 unrelated French families segregating SCA19. Eleven patients had a classic phenotype with slowly progressive cerebellar ataxia with predominant gait impairment. Mean age of ataxia onset was 23.1 years, although age at onset ranged from 2 to 66 years. Mild parkinsonism (defined as an association of rigidity and akinesia associated with a rest tremor) was seen in 8 patients. Epilepsy was seen in 5 patients, with a median age of onset of 5.3 years (range, 3-12 years). Of the 7 patients who had brain MRIs, 5 had isolated atrophy of the vermis. Most patients had learning difficulties and 5 had attended special schools. Of the 15 patients for whom cognitive function was assessed, 12 had mild cognitive impairment. Behavioral issues were seen in 4 patients.
Kurihara et al. (2018) reported a 30-year-old Japanese man with SCA19. He had developmental delay, with head control attained at age 8 months and walking at age 20 months. Beginning at age 15 years, he required a special support school. At age 18 years, he began to have difficulty with word articulation, paroxysmal jerking of his trunk, and involuntary pronation of his right arm. He was noted to have an unsteady gait at age 24 years. Intellectual deterioration was not observed. A neuropsychologic test at age 30 showed a full scale IQ of 59. EEG showed bursts of high-amplitude sharp waves after photic stimulation or during hyperventilation. Brain MRI showed cerebellar atrophy.
Hsiao et al. (2019) reported 3 patients in 2 unrelated families with SCA19: a 24-year-old male (pedigree A) and a 69-year-old mother and her 39-year-old son (pedigree B). Initial presentation was developmental delay or cognitive impairment in the 2 male patients, and gait disturbance in the mother. Onset of ataxia ranged from age 10 to 36 years. Movement disorders, including myoclonus, dystonia, and bradykinesia, were seen in the 2 males. Neuroimaging in the males showed atrophy of the cerebrum, cerebellar hemisphere, and vermis; neuroimaging was not performed on the mother.
The transmission pattern of SCA19 in the families reported by Schelhaas et al. (2001) and Chung et al. (2003) was consistent with autosomal dominant inheritance.
Using a genomewide screen in the large Dutch ADCA family studied by Schelhaas et al. (2001), Verbeek et al. (2002) mapped the disorder, designated SCA19, to chromosome 1p21-q21 (maximum 2-point lod score of 3.82 at theta = 0.0 with marker D1S534). Multipoint and haplotype analysis defined a candidate interval of about 35 cM.
By genomewide analysis of a Han Chinese family with ADCA, Chung et al. (2003) identified a candidate disease locus, termed SCA22, at chromosome 1p21-q23 (maximum multipoint lod score of 3.78 at marker D1S1167). Haplotype analysis defined a 43.7-cM interval flanked by D1S206 and D1S2878.
Schelhaas et al. (2004) asserted that the SCA19 and SCA22 loci represented the same disease-causing gene. Chung and Soong (2004) stated that the features in their family were different from those reported by Schelhaas et al. (2001), but also noted that it is unlikely that there are 2 different genes causing SCA within the candidate region.
In affected members of a Han Chinese family with SCA, originally reported by Chung et al. (2003), Lee et al. (2012) identified a heterozygous 3-bp deletion in the KCND3 gene (605411.0001). The same heterozygous deletion was found in affected members of a French family with autosomal dominant SCA. The mutation, which was found by exome sequencing and confirmed by Sanger sequencing, segregated with the disorder in both families. In HEK293 cells, the mutant protein showed no discernible surface expression and appeared to be abnormally retained within the endoplasmic reticulum. Voltage-clamp recordings showed decreased outward potassium currents compared to wildtype cells in response to voltage. Three additional heterozygous missense variants were found in the KCND3 gene (G345V, V338E, or T377M) in an Ashkenazi Jewish family and in 3 of 55 Japanese families with late-onset SCA, but segregation of the variants with the phenotype was unclear and no functional studies were performed on these variants. No KCND3 mutations were found in probands from 105 Chinese families with hereditary ataxia.
In affected members of a large Dutch family with SCA, originally reported by Schelhaas et al. (2001), Duarri et al. (2012) identified a heterozygous mutation in the KCND3 gene (T352P; 605411.0002). The mutation, which was found by whole-exome sequencing and confirmed by Sanger sequencing, segregated with the disorder in the family. Transfection of the mutation into HeLa cells showed that the mutant protein had almost no cell surface expression, but rather accumulated in the endoplasmic reticulum, consistent with a trafficking defect. The mutant protein was more rapidly degraded compared to the wildtype protein, suggesting that it was misfolded. The trafficking and degradation defects could be rescued by coexpression with the active isoform of KCHIP2 (604661). Patch-clamp recordings showed that the mutant channel had almost no detectable current activity (1% compared to wildtype). Duarri et al. (2012) suggested a dominant-negative effect and hypothesized that abnormal channel function may cause cellular toxicity due to abnormal intracellular calcium homeostasis, defects in long-term potentiation or depression, or chronic activation of the ER stress response. Two additional missense variants were identified in 2 probands, but segregation of the variants within the families was unclear.
In a 10-year-old boy with SCA19, Smets et al. (2015) identified a de novo heterozygous 9-bp duplication in the KCND3 gene (605411.0008). The mutation, which was identified by whole-exome sequencing and confirmed by Sanger sequencing, segregated with the disorder in the family. Studies to assess the effects of the duplication showed that the mutant protein was properly localized in the cell, but that it had significantly decreased stability. The mutation caused a strong shift in the voltage-dependence of activation and inactivation.
In 16 patients from 2 unrelated French families with SCA19, Huin et al. (2017) identified the 3-bp deletion in the KCND3 gene (605411.0001) that had previously been reported by Lee et al. (2012). In addition to typical features associated with SCA, 8 patients had mild parkinsonism and 5 had epilepsy.
In a 30-year-old Japanese man with SCA19, Kurihara et al. (2018) identified a de novo heterozygous missense mutation in the KCND3 gene (G384S; 605411.0009). The mutation, which was found by trio whole-exome sequencing and confirmed by Sanger sequencing, was not present in the ExAC database or an in-house dataset of 800 healthy persons.
By screening of a Han Chinese cohort of patients with inherited cerebellar ataxias in Taiwan, Hsiao et al. (2019) identified 2 heterozygous mutations in the KCND3 gene: a de novo c.950G-A transition in exon 2, resulting in a cys317-to-tyr (C317Y) substitution in 1 patient, and a c.1123C-T transition in exon 3, resulting in a pro375-to-ser (P375S) substitution in a mother and son. The authors then performed functional studies on these 2 mutations as well as on 2 previously reported missense mutations in the KCND3 gene. Electrophysiologic analyses showed that the mutations were associated with loss-of-function phenotypes. Additional studies showed that the mutations were associated with protein degradation and abnormal membrane trafficking. Coexpression of the wildtype with disease-related mutations provided evidence of dominant-negative effects of the mutations on protein biosynthesis and voltage-dependent gating of the Kv4.3 wildtype channel.
Chung, M., Lu, Y.-C., Cheng, N.-C., Soong, B.-W. A novel autosomal dominant spinocerebellar ataxia (SCA22) linked to chromosome 1p21-q23. Brain 126: 1293-1299, 2003. [PubMed: 12764052] [Full Text: https://doi.org/10.1093/brain/awg130]
Chung, M., Soong, B. Reply to: SCA-19 and SCA-22: evidence for one locus with a worldwide distribution. (Letter) Brain 127: e7, 2004. Note: Electronic Article.
Duarri, A., Jezierska, J., Fokkens, M., Meijer, M., Schelhaas, H. J., den Dunnen, W. F. A., van Dijk, F., Verschuuren-Bemelmans, C., Hageman, G., van de Vlies, P., Kusters, B., van de Warrenburg, B. P., Kremer, B., Wijmenga, C., Sinke, R. J., Swertz, M. A., Kampinga, H. H., Boddeke, E., Verbeek, D. S. Mutations in potassium channel KCND3 cause spinocerebellar ataxia type 19. Ann. Neurol. 72: 870-880, 2012. [PubMed: 23280838] [Full Text: https://doi.org/10.1002/ana.23700]
Hsiao, C. T., Fu, S. J., Liu, Y. T., Lu, Y. H., Zhong, C. Y., Tang, C. Y., Soong, B. W., Jeng, C. J. Novel SCA19/22-associated KCND3 mutations disrupt human KV 4.3 protein biosynthesis and channel gating. Hum. Mutat. 40: 2088-2107, 2019. [PubMed: 31293010] [Full Text: https://doi.org/10.1002/humu.23865]
Huin, V., Strubi-Vuillaume, I., Dujardin, K., Brion, M., Delliaux, M., Dellacherie, D., Cuvellier, J. C., Cuisset, J. M., Riquet, A., Moreau, C., Defebvre, L., Sablonniere, B., Devos, D. Expanding the phenotype of SCA19/22: parkinsonism, cognitive impairment and epilepsy. Parkinsonism Relat. Disord. 45: 85-89, 2017. [PubMed: 28947073] [Full Text: https://doi.org/10.1016/j.parkreldis.2017.09.014]
Kurihara, M., Ishiura, H., Sasaki, T., Otsuka, J., Hayashi, T., Terao, Y., Matsukawa, T., Mitsui, J., Kaneko, J., Nishiyama, K., Doi, K., Yoshimura, J., Morishita, S., Shimizu, J., Tsuji, S. Novel de novo KCND3 mutation in a Japanese patient with intellectual disability, cerebellar ataxia, myoclonus, and dystonia. Cerebellum 17: 237-242, 2018. [PubMed: 28895081] [Full Text: https://doi.org/10.1007/s12311-017-0883-4]
Lee, Y.-C., Durr, A., Majczenko, K., Huang, Y.-H., Liu, Y.-C., Lien, C.-C., Tsai, P.-C., Ichikawa, Y., Goto, J., Monin, M.-L., Li, J. Z., Chung, M.-Y., and 10 others. Mutations in KCND3 cause spinocerebellar ataxia type 22. Ann. Neurol. 72: 859-869, 2012. [PubMed: 23280837] [Full Text: https://doi.org/10.1002/ana.23701]
Schelhaas, H. J., Ippel, P. F., Hageman, G., Sinke, R. J., van der Laan, E. N., Beemer, F. A. Clinical and genetic analysis of a four-generation family with a distinct autosomal dominant cerebellar ataxia. J. Neurol. 248: 113-120, 2001. [PubMed: 11284128] [Full Text: https://doi.org/10.1007/s004150170245]
Schelhaas, H. J., Verbeek, D. S., Van de Warrenburg, B. P. C., Sinke, R. J. SCA19 and SCA22: evidence for one locus with a worldwide distribution. (Letter) Brain 127: e6, 2004. Note: Electronic Article. [PubMed: 14679032] [Full Text: https://doi.org/10.1093/brain/awh036]
Smets, K., Duarri, A., Deconinck, T., Ceulemans, B., van de Warrenburg, B. P., Zuchner, S., Gonzalez, M. A., Schule, R., Synofzik, M., Van der Aa, N., De Jonghe, P., Verbeek, D. S., Baets, J. First de novo KCND3 mutation causes severe Kv4.3 channel dysfunction leading to early onset cerebellar ataxia, intellectual disability, oral apraxia and epilepsy. BMC Med. Genet. 16: 51, 2015. [PubMed: 26189493] [Full Text: https://doi.org/10.1186/s12881-015-0200-3]
Verbeek, D. S., Schelhaas, J. H., Ippel, E. F., Beemer, F. A., Pearson, P. L., Sinke, R. J. Identification of a novel SCA locus (SCA19) in a Dutch autosomal dominant cerebellar ataxia family on chromosome region 1p21-q21. Hum. Genet. 111: 388-393, 2002. [PubMed: 12384780] [Full Text: https://doi.org/10.1007/s00439-002-0782-7]