A rare sequence variant in intron 1 of THAP1 is associated with primary dystonia

Although coding variants in THAP1 have been causally associated with primary dystonia, the contribution of noncoding variants remains uncertain. Herein, we examine a previously identified Intron 1 variant (c.71+9C>A, rs200209986). Among 1672 subjects with mainly adult-onset primary dystonia, 12 harbored the variant in contrast to 1/1574 controls (P < 0.01). Dystonia classification included cervical dystonia (N = 3), laryngeal dystonia (adductor subtype, N = 3), jaw-opening oromandibular dystonia (N = 1), blepharospasm (N = 2), and unclassified (N = 3). Age of dystonia onset ranged from 25 to 69 years (mean = 54 years). In comparison to controls with no identified THAP1 sequence variants, the c.71+9C>A variant was associated with an elevated ratio of Isoform 1 (NM_018105) to Isoform 2 (NM_199003) in leukocytes. In silico and minigene analyses indicated that c.71+9C>A alters THAP1 splicing. Lymphoblastoid cells harboring the c.71+9C>A variant showed extensive apoptosis with relatively fewer cells in the G2 phase of the cell cycle. Differentially expressed genes from lymphoblastoid cells revealed that the c.71+9C>A variant exerts effects on DNA synthesis, cell growth and proliferation, cell survival, and cytotoxicity. In aggregate, these data indicate that THAP1 c.71+9C>A is a risk factor for adult-onset primary dystonia

Recent advances in the genetics of dystonia

Dystonia, a common and genetically heterogeneous neurological disorder, was recently defined as a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures, or both. Via the application of whole-exome sequencing, the genetic landscape of dystonia and closely related movement disorders is becoming exposed. In particular, several novel genetic causes have been causally associated with dystonia or dystonia-related disorders over the past 2 years. These genes include PRRT2 (DYT10), CIZ1 (DYT23), ANO3 (DYT24), GNAL (DYT25), and TUBB4A (DYT4). Despite these advances, major gaps remain in identifying the genetic origins for most cases of adult-onset isolated dystonia. Furthermore, model systems are needed to study the biology of PRRT2, CIZ1, ANO3, Gαolf, and TUBB4A in the context of dystonia. This review focuses on these recent additions to the family of dystonia genes, genotype-phenotype correlations, and possible cellular contributions of the encoded proteins to the development of dystonia. © 2014 Springer Science+Business Media

Blepharospasm in a multiplex African-American pedigree

Background Isolated blepharospasm (BSP) is a late-onset focal dystonia characterized by involuntary contractions of the orbicularis oculi muscles. Genetic studies of BSP have been limited by the paucity of large multiplex pedigrees. Although sequence variants (SVs) in THAP1 have been reported in rare cases of BSP, the genetic causes of this focal dystonia remain largely unknown. Moreover, in the absence of family history and strong in silico or in vitro evidence of deleteriousness, the pathogenicity of novel SVs in THAP1 and other dystonia-associated genes can be indeterminate. Methods A large African-American pedigree with BSP was phenotypically characterized and screened for mutations in THAP1, TOR1A and GNAL with Sanger sequencing. Whole-exome sequencing of the proband was used to examine other dystonia-associated genes for potentially pathogenic SVs. In silico and co-segregation analyses were performed for a novel THAP1 SV identified in the proband. Results Seven family members exhibited increased blinking and/or stereotyped bilateral and synchronous orbicularis oculi spasms with age of onset ranging from early childhood to late adult life (7 to 54 years). The proband was found to harbor a novel THAP1 SV (c.314T \u3e C, p.L105S). However, the p.L105S SV did not co-segregate with blepharospasm in the pedigree. Moreover, in silico analyses suggest that p.L105S is benign. No pathogenic or likely pathogenic SVs in other dystonia-associated genes were identified with whole-exome sequencing. Conclusions Blepharospasm can be familial and may be hereditary in African-Americans. A comprehensive array of in silico tools, and, if possible, co-segregation analysis should be used to classify SVs in dystonia-associated genes

Pathogenic variants in TUBB4A are not found in primary dystonia

Objective: To determine the contribution of TUBB4A, recently associated with DYT4 dystonia in a pedigree with whispering dysphonia from Norfolk, United Kingdom, to the etiopathogenesis of primary dystonia. Methods: High-resolution melting and Sanger sequencing were used to inspect the entire coding region of TUBB4A in 575 subjects with primary laryngeal, segmental, or generalized dystonia. Results: No pathogenic variants, including the exon 1 variant (c.4C\u3eG) identified in the DYT4 whispering dysphonia kindred, were found in this study. Conclusion: The c.4C\u3eG DYT4 mutation appears to be private, and clinical testing for TUBB4A mutations is not justified in spasmodic dysphonia or other forms of primary dystonia. Moreover, given its allelic association with leukoencephalopathy hypomyelination with atrophy of basal ganglia and cerebellum and protean clinical manifestations (chorea, ataxia, dysarthria, intellectual disability, dysmorphic facial features, and psychiatric disorders), DYT4 should not be categorized as a primary dystonia. © 2014 American Academy of Neurology

GNAL mutations cause adult-onset primary dystonia

OBJECTIVE: Identification of the causal mutation in an African-American family with adult-onset primary dystonia. BACKGROUND: The vast majority of patients with dystonia are adults with primary focal or segmental anatomical distributions. Familial and sporadic dystonia appear to share the same genetic etiological background. Although approximately 10% of probands have at least one first- or second-degree relative with dystonia, large pedigrees suited for linkage analysis are uncommon. In previous work, we excluded THAP1 and TOR1A mutations in an African-American family with clinical phenotypes that included cervical, laryngeal and hand-forearm dystonia. DESIGN/METHODS: Linkage and haplotype analyses were combined with solution-based whole-exome capture and massively parallel sequencing in order to identify the causal mutation (GNAL, c.913G>T) in our African-American family with dystonia. High resolution melting and Sanger sequencing were used to screen 768 additional subjects with primary cervical or segmental dystonia for sequence variants in GNAL. RESULTS: The missense mutation in GNAL (c.913G>T, p.V305F) was found to co-segregate with dystonia in our African-American pedigree. GNAL encodes guanine nucleotide-binding protein G(olf), subunit alpha [Gα(olf)]. Gα(olf) is highly expressed in the olfactory bulb, striatum and cerebellar Purkinje cells. Gα(olf) plays a role in olfaction, coupling D1 and A2a receptors to adenylyl cyclase, and histone H3 phosphorylation. Screening identified two additional pedigrees with GNAL mutations (c.822-823insA [p.R275T∗13] and c.964C>T [p.R322∗]). None of these sequence variants were found in 760 controls. CONCLUSIONS: Mutations in GNAL are causally-associated with adult-onset primary cervical and segmental dystonia. The prominent expression of Gα(olf) in striatum and cerebellar Purkinje cells points to potential sites of functional pathology in primary dystonia

Whole-exome sequencing for variant discovery in blepharospasm

Background: Blepharospasm (BSP) is a type of focal dystonia characterized by involuntary orbicularis oculi spasms that are usually bilateral, synchronous, and symmetrical. Despite strong evidence for genetic contributions to BSP, progress in the field has been constrained by small cohorts, incomplete penetrance, and late age of onset. Although several genetic etiologies for dystonia have been identified through whole-exome sequencing (WES), none of these are characteristically associated with BSP as a singular or predominant manifestation. Methods: We performed WES on 31 subjects from 21 independent pedigrees with BSP. The strongest candidate sequence variants derived from in silico analyses were confirmed with bidirectional Sanger sequencing and subjected to cosegregation analysis. Results: Cosegregating deleterious variants (GRCH37/hg19) in CACNA1A (NM_001127222.1: c.7261_7262delinsGT, p.Pro2421Val), REEP4 (NM_025232.3: c.109C\u3eT, p.Arg37Trp), TOR2A (NM_130459.3: c.568C\u3eT, p.Arg190Cys), and ATP2A3 (NM_005173.3: c.1966C\u3eT, p.Arg656Cys) were identified in four independent multigenerational pedigrees. Deleterious variants in HS1BP3 (NM_022460.3: c.94C\u3eA, p.Gly32Cys) and GNA14 (NM_004297.3: c.989_990del, p.Thr330ArgfsTer67) were identified in a father and son with segmental cranio-cervical dystonia first manifest as BSP. Deleterious variants in DNAH17, TRPV4, CAPN11, VPS13C, UNC13B, SPTBN4, MYOD1, and MRPL15 were found in two or more independent pedigrees. To our knowledge, none of these genes have previously been associated with isolated BSP, although other CACNA1A mutations have been associated with both positive and negative motor disorders including ataxia, episodic ataxia, hemiplegic migraine, and dystonia. Conclusions: Our WES datasets provide a platform for future studies of BSP genetics which will demand careful consideration of incomplete penetrance, pleiotropy, population stratification, and oligogenic inheritance patterns

Mutations in CIZ1 cause adult onset primary cervical dystonia

Objective: Primary dystonia is usually of adult onset, can be familial, and frequently involves the cervical musculature. Our goal was to identify the causal mutation in a family with adult onset, primary cervical dystonia. Methods: Linkage and haplotype analyses were combined with solution-based whole-exome capture and massively parallel sequencing in a large Caucasian pedigree with adult onset, primary cervical dystonia to identify a cosegregating mutation. High-throughput screening and Sanger sequencing were completed in 308 Caucasians with familial or sporadic adult onset cervical dystonia and matching controls for sequence variants in this mutant gene. Results: Exome sequencing led to the identification of an exonic splicing enhancer mutation in exon 7 of CIZ1 (c.790A\u3eG, p.S264G), which encodes CIZ1, Cip1-interacting zinc finger protein 1. CIZ1 is a p21 Cip1/Waf1-interacting zinc finger protein expressed in brain and involved in DNA synthesis and cell-cycle control. Using a minigene assay, we showed that c.790A\u3eG altered CIZ1 splicing patterns. The p.S264G mutation also altered the nuclear localization of CIZ1. Screening in subjects with adult-onset cervical dystonia identified 2 additional CIZ1 missense mutations (p.P47S and p.R672M). Interpretation: Mutations in CIZ1 may cause adult onset, primary cervical dystonia, possibly by precipitating neurodevelopmental abnormalities that manifest in adults and/or G1/S cell-cycle dysregulation in the mature central nervous system. Copyright © 2012 American Neurological Association

Motor phenotypes and molecular networks associated with germline deficiency of Ciz1

A missense mutation in CIZ1 (c.790A \u3e G, p.S264G) was linked to autosomal dominant cervical dystonia in a large multiplex Caucasian pedigree (OMIM614860, DYT23). CIZ1 is a p21 (Cip1/Waf1) -interacting zinc finger protein, widely expressed in neural and extra-neural tissues, and plays a role in DNA synthesis at the G1/S cell-cycle checkpoint. The role of CIZ1 in the nervous system and relative contributions of gain- or loss- of function to the pathogenesis of CIZ1-associated dystonia remain indefinite. Using relative quantitative reverse transcriptase-PCR, cerebellum showed the highest expression levels of Ciz1 in adult mouse brain, over two fold higher than liver, and higher than striatum, midbrain and cerebral cortex. Overall, neural expression of Ciz1 increased with postnatal age. A Ciz1 gene-trap knock-out (KO) mouse model (Ciz1 -/- ) was generated to examine the functional role(s) of CIZ1 in the sensorimotor nervous system and contributions of CIZ1 to cell-cycle control in the mammalian brain. Ciz1 transcripts were absent in Ciz1 -/- mice and reduced by approximately 50% in Ciz1 +/- mice. Ciz1 -/- mice were fertile but smaller than wild-type (WT) littermates. Ciz1 -/- mice did not manifest dystonia, but exhibited mild motoric abnormalities on balance, open-field activity, and gait. To determine the effects of germline KO of Ciz1 on whole-genome gene expression in adult brain, total RNA from mouse cerebellum was harvested from 6 10-month old Ciz1 -/- mice and 6 age- and gender- matched WT littermates for whole-genome gene expression analysis. Based on whole-genome gene-expression analyses, genes involved in cellular movement, cell development, cellular growth, cellular morphology and cell-to-cell signaling and interaction were up-regulated in Ciz1 -/- mice. The top up-regulated pathways were metabolic and cytokine-cytokine receptor interactions. Down-regulated genes were involved in cell cycle, cellular development, cell death and survival, gene expression and cell morphology. Down-regulated networks included those related to metabolism, focal adhesion, neuroactive ligand-receptor interaction, and MAPK signaling. Based on pathway analyses, transcription factor 7-like 2 (TCF7L2), a member of the Wnt/β-catenin signaling pathway, was a major hub for down-regulated genes, whereas NF-κB was a major hub for up-regulated genes. In aggregate, these data suggest that CIZ1 may be involved in the post-mitotic differentiation of neurons in response to external signals and changes in gene expression may compensate, in part, for CIZ1 deficiency in our Ciz1 -/- mouse model. Although CIZ1 deficiency was associated with mild motor abnormalities, germline loss of Ciz1 was not associated with dystonia on the C57BL/6J background

Clinical and genetic features of cervical dystonia in a large multicenter cohort

Objective: To characterize the clinical and genetic features of cervical dystonia (CD). Methods: Participants enrolled in the Dystonia Coalition biorepository (NCT01373424) with initial manifestation as CD were included in this study (n 1,000). Data intake included demographics, family history, and the Global Dystonia Rating Scale. Participants were screened for sequence variants (SVs) in GNAL, THAP1, and Exon 5 of TOR1A. Results: The majority of participants were Caucasian (95%) and female (75%). The mean age at onset and disease duration were 45.5 ± 13.6 and 14.6 ± 11.8 years, respectively. At the time of assessment, 68.5% had involvement limited to the neck, shoulder(s), and proximal arm(s), whereas 47.4% had dystonia limited to the neck. The remaining 31.5% of the individuals exhibited more extensive anatomical spread. A head tremor was noted in 62% of the patients. Head tremor and laryngeal dystonia were more common in females. Psychiatric comorbidities, mainly depression and anxiety, were reported by 32% of the participants and were more common in females. Family histories of dystonia, parkinsonian disorder, and tremor were present in 14%, 11%, and 29% of the patients, respectively. Pathogenic or likely pathogenic SVs in THAP1, TOR1A, and GNAL were identified in 8 participants (0.8%). Two individuals harbored novel missense SVs in Exon 5 of TOR1A. Synonymous and noncoding SVs in THAP1 and GNAL were identified in 4% of the cohort. Conclusions: Head tremor, laryngeal dystonia, and psychiatric comorbidities are more common in female participants with CD. Coding and noncoding variants in GNAL, THAP1, and TOR1A make small contributions to the pathogenesis of CD