Introduction: Mutations in gap junction protein beta 1 (GJB1) on the X chromosome represent one of the most common causes of hereditary neuropathy. We assessed manifestations associated with a rare 3 untranslated region mutation (UTR) of GJB1 in a large family with X-linked Charcot-Marie-Tooth disease (CMTX). Methods: Clinical, electrophysiological, and molecular genetic analyses were performed on an 8-generation family with CMTX. Results: There were 22 affected males and 19 symptomatic females, including an 83-year-old woman followed for 40 years. Electrophysiological studies showed a primarily axonal neuropathy. The c.*15C>T mutation in the GJB1 3 UTR was identified in 4 branches of the family with a log of odds (LOD) of 4.91. This created a BstE II enzyme recognition site that enabled detection by restriction digestion. Discussion: The c.*15C>T mutation in the GJB1 3 UTR segregates with CMTX1 in 8 generations. Penetrance in males and females is essentially complete. A straightforward genetic method to detect this mutation is described. Muscle Nerve57: 859-862, 2018

Childhood apraxia of speech (CAS) is a severe and socially debilitating form of speech sound disorder with suspected genetic involvement, but the genetic etiology is not yet well understood. Very few known or putative causal genes have been identified to date, e.g., FOXP2 and BCL11A. Building a knowledge base of the genetic etiology of CAS will make it possible to identify infants at genetic risk and motivate the development of effective very early intervention programs. We investigated the genetic etiology of CAS in two large multigenerational families with familial CAS. Complementary genomic methods included Markov chain Monte Carlo linkage analysis, copy-number analysis, identity-by-descent sharing, and exome sequencing with variant filtering. No overlaps in regions with positive evidence of linkage between the two families were found. In one family, linkage analysis detected two chromosomal regions of interest, 5p15.1-p14.1, and 17p13.1-q11.1, inherited separately from the two founders. Single-point linkage analysis of selected variants identified CDH18 as a primary gene of interest and additionally, MYO10, NIPBL, GLP2R, NCOR1, FLCN, SMCR8, NEK8, and ANKRD12, possibly with additive effects. Linkage analysis in the second family detected five regions with LOD scores approaching the highest values possible in the family. A gene of interest was C4orf21 (ZGRF1) on 4q25-q28.2. Evidence for previously described causal copy-number variations and validated or suspected genes was not found. Results are consistent with a heterogeneous CAS etiology, as is expected in many neurogenic disorders. Future studies will investigate genome variants in these and other families with CAS.

Ataxia-pancytopenia (AP) syndrome is characterized by cerebellar ataxia, variable hematologic cytopenias, and predisposition to marrow failure and myeloid leukemia, sometimes associated with monosomy 7. Here, in the four-generation family UW-AP, linkage analysis revealed four regions that provided the maximal LOD scores possible, one of which was in a commonly microdeleted chromosome 7q region. Exome sequencing identified a missense mutation (c.2640C>A, p.His880Gln) in the sterile alpha motif domain containing 9-like gene (SAMD9L) that completely cosegregated with disease. By targeted sequencing of SAMD9L, we subsequently identified a different missense mutation (c.3587G>C, p.Cys1196Ser) in affected members of the first described family with AP syndrome, Li-AP. Neither variant is reported in the public databases, both affect highly conserved amino acid residues, and both are predicted to be damaging. With time in culture, lymphoblastic cell lines (LCLs) from two affected individuals in family UW-AP exhibited copy-neutral loss of heterozygosity for large portions of the long arm of chromosome 7, resulting in retention of only the wild-type SAMD9L allele. Newly established LCLs from both individuals demonstrated the same phenomenon. In addition, targeted capture and sequencing of SAMD9L in uncultured blood DNA from both individuals showed bias toward the wild-type allele. These observations indicate in vivo hematopoietic mosaicism. The hematopoietic cytopenias that characterize AP syndrome and the selective advantage for clones that have lost the mutant allele support the postulated role of SAMD9L in the regulation of cell proliferation. Furthermore, we show that AP syndrome is distinct from the dyskeratoses congenita telomeropathies, with which it shares some clinical characteristics.

Objective: To identify the cause of a complex autosomal dominant spinocerebellar ataxia (SCA) with hematologic cytopenias. Background: SCAs remain the continuously enlarging group of genetically heterogeneous disease group. We identified a family with a cerebellar ataxia and variable hematologic cytopenias. Known genes or loci for SCA or pancytopenia were excluded by sequence or targeted linkage analysis. Design/Methods: Nine people in three generations of a family manifested nystagmus and imbalance that slowly progresses to a full cerebellar syndrome. The age of onset ranged from 8 to 55. Hematologic cytopenias were widely variable in age of onset, blood cell lines involved, and severity. Autopsy on one subject who was neurologically normal but died of a retroperitoneal bleed at age of 16 revealed predominant Purkinje cell loss. To identify the causal gene, we exploited a combination of genomic technologies, including exome resequencing and SNP-based linkage and identity-by-descent (IBD) analyses. Results: After stepwise filtering to remove common and non-functional variants, heterozygous variants shared by two exomes were confirmed by PCR-sequencing, but no variant co-segregated with disease in the rest of the family. SNP linkage and IBD analyses detected four shared regions. In a sample derived from a lymphocyte cell line, the array revealed a region of loss of heterozygosity (LOH) that overlapped with one linkage region. After excluding this sample, one variant in the LOH region co-segregated with disease. This variant is not reported in dbSNP, EVS or 1000K databases, is predicted damaging by both Polyphen-2 and SIFT, and shows high conservation by PhastCons. Conclusions: A combination of exome sequencing and SNP array identified a strong candidate gene for a unique SCA characterized by both ataxia and cytopenias. This gene is not well characterized but lies in a region commonly deleted in myelopdysplasia and has been reported to be associated with myeloid leukemia. Functional studies on the effect of this mutation are ongoing.

PHARC (polyneuropathy, hearing loss, ataxia, retinitis pigmentosa, and cataracts) is a recently described autosomal-recessive neurodegenerative disease caused by mutations in the --hydrolase domain-containing 12 gene (ABHD12). Only five homozygous ABHD12 mutations have been reported and the pathogenesis of PHARC remains unclear. We evaluated a woman who manifested short stature as well as the typical features of PHARC. Sequence analysis of ABHD12 revealed a novel heterozygous c.1129A>T (p.Lys377*) mutation. Targeted comparative genomic hybridization detected a 59-kb deletion that encompasses exon 1 of ABHD12 and exons 1-4 of an adjacent gene, GINS1, and includes the promoters of both genes. The heterozygous deletion was also carried by the patient's asymptomatic mother. Quantitative reverse transcription-PCR demonstrated approximate to 50% decreased expression of ABHD12RNA in lymphoblastoid cell lines from both individuals. Activity-based protein profiling of serine hydrolases revealed absence of ABHD12 hydrolase activity in the patient and 50% reduction in her mother. This is the first report of compound heterozygosity in PHARC and the first study to describe how a mutation might affect ABHD12 expression and function. The possible involvement of haploinsufficiency for GINS1, a DNA replication complex protein, in the short stature of the patient and her mother requires further studies. (C) 2013 Wiley Periodicals, Inc.

Objective: Genetic study of a patient with progressive Polyneuropathy, Hearing loss, Ataxia, Retinitis pigmentosa, and Cataracts (PHARC). Background PHARC is a recently described autosomal recessive neurodegenerative disease caused by mutations in the anhydrolase domain containing 12 gene (ABHD12) that encodes an enzyme that catalyzes the hydrolysis of 2-arachidonoyl glycerol. Only four homozygous loss-of-function ABHD12 mutations have been reported to date. Design/Methods: We ascertained a 29-year-old woman of Northern European background who manifested the typical features of PHARC. Protein-coding exons of ABHD12 were sequenced in DNA from the patient and her unaffected mother and maternal half-brother. The ABHD12 deletion boundaries were determined by comparative genomic hybridization (CGH) on an array containing 106 oligonucleotide probes with ∼3 kb mean spacing. Quantitative PCR (qPCR) was performed on the patient9s lymphoblastoid line RNA. Results: The patient manifested congenital foot deformities requiring surgery, childhood-onset progressive hearing loss requiring cochlear implants, adolescent-onset cataracts with retinitis pigmentosa and macular edema, and a demyelinating motor/sensory peripheral neuropathy. Her brain MRI was normal. In addition, she and her unaffected mother both have short stature, 4911", whereas her unaffected maternal half-brother has normal height. Sequencing of ABHD12 in the patient identified a novel 1129a→t (Lys377X) mutation in exon 12. Targeted CGH detected a 59 kb deletion that encompassed exon 1 of ABHD12 and exons 1-4 of an adjacent gene, GINS1, and includes the promoters of both genes. The deletion was found in the mother but not in the maternal half-brother. RNA qPCR revealed remarkably decreased expression of ABHD12 in the patient. Conclusions: We report a fifth ABHD12 mutation and the first instance of compound heterozygosity in PHARC. The mutations severely reduce ABHD12 expression; effect on hydrolase activity is under investigation. The possible involvement of haploinsufficiency for GINS1, a DNA replication complex protein, in the short stature of the patient and her mother requires further study. Supported by: The Department of Veterans Affairs and R01 NS069719-01. Disclosure: Dr. Chen has received license fee payments from Athena Diagnostics. Dr. Davis has nothing to disclose. Dr. Mefford has nothing to disclose. Dr. Sul has nothing to disclose. Dr. Naydenov has nothing to disclose. Dr. Barloon has nothing to disclose. Dr. Wolff has nothing to disclose. Dr. Matsushita has nothing to disclose. Dr. Smith has nothing to disclose. Dr. Stella has nothing to disclose. Dr. Raskind has received (royalty or license fee or contractual rights) payments from Athena Diagnostics. Dr. Bird has received personal compensation for activities with Athena Diagnostics for speakers bureau and licensing fees.Dr. Bird has received liscensing payments from Athena Diagnostics.

The parkinsonian syndromes comprise a highly heterogeneous group of disorders. Although 15 loci are linked to predominantly familial Parkinson's disease (PD), additional PD loci are likely to exist. We recently identified a multigenerational family of Danish and German descent in which five males in three generations presented with a unique syndrome characterized by parkinsonian features and variably penetrant spasticity for which X‐linked disease transmission was strongly suggested (XPDS). Autopsy in one individual failed to reveal synucleinopathy; however, there was a significant four‐repeat tauopathy in the striatum. Our objective was to identify the locus responsible for this unique parkinsonian disorder. Members of the XPDS family were genotyped for markers spanning the X chromosome. Two‐point and multipoint linkage analyses were performed and the candidate region refined by analyzing additional markers. A multipoint LODmax score of 2.068 was obtained between markers DXS991 and DXS993. Haplotype examination revealed an ∼20 cM region bounded by markers DXS8042 and DXS1216 that segregated with disease in all affected males and obligate carrier females and was not carried by unaffected at‐risk males. To reduce the possibility of a false‐positive linkage result, multiple loci and genes associated with other parkinsonian or spasticity syndromes were excluded. In conclusion, we have identified a unique X‐linked parkinsonian syndrome with variable spasticity and four‐repeat tau pathology, and defined a novel candidate gene locus spanning ∼28 Mb from Xp11.2–Xq13.3. © 2010 Movement Disorder Society

Background: Recently, mutations in the transient receptor potential cation channel, subfamily V, member 4 gene (TRPV4) have been reported in Charcot-Marie-Tooth Type 2C (CMT2C) with vocal cord paresis. Other mutations in this same gene have been described in separate families with various skeletal dysplasias. Further clarification is needed of the different phenotypes associated with this gene. Methods: We performed clinical evaluation, electrophysiology, and genetic analysis of the TRPV4 gene in 2 families with CMT2C. Results: Two multigenerational families had a motor greater than sensory axonal neuropathy associated with variable vocal cord paresis. The vocal cord paresis varied from absent to severe, requiring permanent tracheotomy in 2 subjects. One family with mild neuropathy also manifested pronounced short stature, more than 2 SD below the average height for white Americans. There was one instance of dolichocephaly. A novel S542Y mutation in the TRPV4 gene was identified in this family. The other family had a more severe, progressive, motor neuropathy with sensory loss, but less remarkable short stature and an R315W mutation in TRPV4. Third cranial nerve involvement and sleep apnea occurred in one subject in each family. Conclusion: CMT2C with axonal neuropathy, vocal cord paresis, and short stature is a unique syndrome associated with mutations in the TRPV4 gene. Mutations in TRPV4 can cause abnormalities in bone, peripheral nerve, or both and may result in highly variable orthopedic and neurologic phenotypes.

An X-linked myopathy was recently associated with mutations in the four-and-a-half-LIM domains 1 (FHL1) gene. We identified a family with late onset, slowly progressive weakness of scapuloperoneal muscles in three brothers and their mother. A novel missense mutation in the LIM2 domain of FHL1 (W122C) co-segregated with disease in the family. The phenotype was less severe than that in other reported families. Muscle biopsy revealed myopathic changes with FHL1 inclusions that were ubiquitin- and desmin-positive. This mutation provides additional evidence for X-linked myopathy caused by a narrow spectrum of mutations in FHL1, mostly in the LIM2 domain. Molecular dynamics (MD) simulations of the newly identified mutation and five previously published missense mutations in the LIM2 domain revealed no major distortions of the protein structure or disruption of zinc binding. There were, however, increases in the nonpolar, solvent-accessible surface area in one or both of two clusters of residues, suggesting that the mutant proteins have a variably increased propensity to aggregate. Review of the literature shows a wide range of phenotypes associated with mutations in FHL1. However, recognizing the typical scapuloperoneal phenotype and X-linked inheritance pattern will help clinicians arrive at the correct diagnosis.

We previously reported a five-generation family manifesting an autosomal dominant disorder of facial myokymia and dystonic/choreic movements (FDFM). The dyskinetic episodes are initially paroxysmal but may become constant. With increasing age they may lessen or even disappear. The previous study excluded nine candidate genes chosen for their association with myokymia or chorea and two regions containing single or clustered ion channel genes. We now report identification by whole genome linkage analysis of a broad region on chromosome 3p21-3q21 that segregates with the disease in all 10 affected members in three generations who participated in the study. GENEHUNTER-MODSCORE Version 2.0.1 provided a maximum multipoint LOD score of 3.099. No other disorders primarily characterized by myokymia, dystonia, or chorea are known to map to this region. Identification of additional families with FDFM may narrow the critical region and facilitate the choice of candidate genes for further analysis.

BACKGROUND Paroxysmal nonkinesigenic dyskinesia (PNKD) is a rare disorder characterized by attacks of involuntary movements brought on by stress, alcohol, or caffeine, but not by movement. An autosomal dominant form of this disorder was mapped to chromosome 2q33-36, and different missense mutations in exon 1 of the myofibrillogenesis regulator 1 (MR1) gene were identified recently in 2 kindreds. OBJECTIVES To describe studies on a new pedigree with PNKD, to explore the possibility of locus heterogeneity, and to further delineate the spectrum of mutations in MR1 in 2 families with PNKD. DESIGN, SETTING, AND PATIENTS All 10 exons of MR1 were sequenced in DNA from members of 2 pedigrees with autosomal dominant PNKD. RESULTS Different missense mutations in exon 1 of MR1 that cosegregate with disease were identified in each multiplex family. These single-nucleotide mutations predicted substitution of valine for alanine in residue 7 in one family and residue 9 in the other. The same mutations were found in the only 2 families previously published. Family history and haplotype analysis make it unlikely that the families with the same mutations are related. CONCLUSIONS The function of MR1 is unknown, but the 2 mutations identified in the 4 families with PNKD studied to date are predicted to disrupt the amino terminal alpha-helix suggesting that this region of the gene is critical for proper gene function under stressful conditions. Study of additional families will be important to determine whether analysis of a single exon (MR1 exon 1) is sufficient for genetic testing purposes.

Spinocerebellar ataxia 14 (SCA14) is associated with missense mutations in the protein kinase C gamma gene (PRKCG), rather than a nucleotide repeat expansion. In this large-scale study of PRKCG in patients with ataxia, two new missense mutations, an in-frame deletion, and a possible splice site mutation were found and can now be added to the four previously described missense mutations. The genotype/phenotype correlations in these families are described.

We report a nonepisodic autosomal dominant (AD) spinocerebellar ataxia (SCA) not caused by a nucleotide repeat expansion that is, to our knowledge, the first such SCA. The AD SCAs currently comprise a group of > or =16 genetically distinct neurodegenerative conditions, all characterized by progressive incoordination of gait and limbs and by speech and eye-movement disturbances. Six of the nine SCAs for which the genes are known result from CAG expansions that encode polyglutamine tracts. Noncoding CAG, CTG, and ATTCT expansions are responsible for three other SCAs. Approximately 30% of families with SCA do not have linkage to the known loci. We recently mapped the locus for an AD SCA in a family (AT08) to chromosome 19q13.4-qter. A particularly compelling candidate gene, PRKCG, encodes protein kinase C gamma (PKC gamma), a member of a family of serine/threonine kinases. The entire coding region of PRKCG was sequenced in an affected member of family AT08 and in a group of 39 unrelated patients with ataxia not attributable to trinucleotide expansions. Three different nonconservative missense mutations in highly conserved residues in C1, the cysteine-rich region of the protein, were found in family AT08, another familial case, and a sporadic case. The mutations cosegregated with disease in both families. Structural modeling predicts that two of these amino acid substitutions would severely abrogate the zinc-binding or phorbol ester-binding capabilities of the protein. Immunohistochemical studies on cerebellar tissue from an affected member of family AT08 demonstrated reduced staining for both PKC gamma and ataxin 1 in Purkinje cells, whereas staining for calbindin was preserved. These results strongly support a new mechanism for neuronal cell dysfunction and death in hereditary ataxias and suggest that there may be a common pathway for PKC gamma-related and polyglutamine-related neurodegeneration.

The autosomal dominant (AD) spinocerebellar ataxias (SCAs) and hereditary sensory neuropathies (HSN) are heterogeneous disorders characterized by variable clinical, electrophysiological, and neuropathological profiles. The SCAs are clinically characterized by slowly progressive incoordination of gait often associated with poor coordination of hands, speech, and eyes. Peripheral neuropathy is not a frequent part of the SCA syndrome. In contrast, the HSNs are primarily characterized by progressive sensory loss. There is substantial clinical overlap between the various SCAs and the various HSNs, and they often cannot be differentiated on the basis of clinical or neuro-imaging studies. We have identified a five-generation American family of Irish ancestry with a unique neurological disorder displaying an AD pattern of inheritance. There was variable expressivity and severity of symptoms including sensory loss, ataxia, pyramidal tract signs, and muscle weakness. Nerve conduction studies were consistent with a sensory axonal neuropathy. Muscle biopsy revealed neurogenic atrophy and brain MRI showed mild cerebellar atrophy. To identify the responsible locus we pursued a whole genome linkage analysis. After analyzing 114 markers, linkage to D7S486 was detected with a two point LOD score of 4.79 at theta = 0.00. Evaluation of additional markers in the region provided a maximum LOD score of 6.36 at theta = 0.00 for marker D7S2554. Haplotype analysis delimited an approximately 14-cM region at 7q22-q32 between markers D7S2418 and D7S1804 cosegregating with the disease. Because this disorder does not easily fall into either the SCA or HSN categories, it is designated sensory/motor neuropathy with ataxia (SMNA).

BACKGROUND:The autosomal dominant spinocerebellar ataxias (SCAs) are a clinically and genetically heterogeneous group of neurodegenerative disorders. Although molecular genetic studies have so far implicated 16 loci in the etiology of these diseases, approximately 30% of families with SCAs remain unlinked.OBJECTIVES:To report the location of a gene causing a "pure" autosomal dominant cerebellar ataxia in one family and to describe the clinical phenotype.PATIENTS:We have identified a 4-generation American family of English and Dutch ethnicity with a pure cerebellar ataxia displaying an autosomal dominant pattern of inheritance. The disease typically has its onset in the third and fourth decades of life, shows no evidence of anticipation, progresses slowly, and does not appear to decrease life expectancy. Clinical DNA testing excluded SCA1, 2, 3, 6, 7, and 8.METHODS:A genome-wide linkage analysis at a 10 centimorgan (cM) level was performed with samples from 26 family members (11 affected, 10 clinically unaffected at risk, and 5 spouses).RESULTS:Assuming 90% penetrance, we found suggestive evidence of linkage to chromosome 19, with a lod score of 2.49 for D19S571. More detailed mapping in this region provided a maximum 2-point lod score of 2.57 at theta = 0 for D19S254 and a maximum multipoint lod score of 4.72 at D19S926. By haplotype construction a 22-cM critical region from D19S601 to the q telomere was defined.CONCLUSIONS:We have mapped a gene for an autosomal dominant SCA to chromosome 19q13.4-qter in one family. The critical region overlaps with the locus for SCA14, a disease described in a single Japanese family and characterized by axial myoclonus. Myoclonus was not seen in the family we studied, but it remains possible that the 2 disorders are allelic variants.

We describe here familial dyskinesia and facial myokymia (FDFM), a novel autosomal dominant disorder characterized by adventitious movements that sometimes appear choreiform and that are associated with perioral and periorbital myokymia. We report a 5‐generation family with 18 affected members (10 males and 8 females) with FDFM. The disorder has an early childhood or adolescent onset. The involuntary movements are paroxysmal at early ages, increase in frequency and severity, and may become constant in the third decade. Thereafter, there is no further deterioration, and there may even be improvement in old age. The adventitious movements are worsened by anxiety but not by voluntary movement, startle, caffeine, or alcohol. The disease is socially disabling, but there is no intellectual impairment or decrease in lifespan. A candidate gene and haplotype analysis was performed in 9 affected and 3 unaffected members from 3 generations of this family using primers for polymorphic loci closely flanking or within genes of interest. We excluded linkage to 11 regions containing genes associated with chorea and myokymia: 1) the Huntington disease gene on chromosome 4p; 2) the paroxysmal dystonic choreoathetosis gene at 2q34; 3) the dentatorubral‐pallidoluysian atrophy gene at 12p13; 4) the choreoathetosis/spasticity disease locus on 1p that lies in a region containing a cluster of potassium (K + ) channel genes; 5) the episodic ataxia type 1 (EA1) locus on 12p that contains the KCNA1 gene and two other voltage‐gated K + channel genes, KCNA5 and KCNA6; 6) the chorea‐acanthocytosis locus on 9q21; 7) the Huntington‐like syndrome on 20p; 8) the paroxysmal kinesigenic dyskinesia locus on 16p11.2‐q11.2; 9) the benign hereditary chorea locus on 14q; 10) the SCA type 5 locus on chromosome 11; and 11) the chromosome 19 region that contains several ion channels and the CACNA1A gene, a brain‐specific P/Q‐type calcium channel gene associated with ataxia and hemiplegic migraine. Our results provide further evidence of genetic heterogeneity in autosomal dominant movement disorders and suggest that a novel gene underlies this new condition. Ann Neurol 2001;49:486–492

OBJECTIVE:To describe a second family with benign hereditary chorea (BCH, OMIM 118700) and suggestive linkage to chromosome 14q. BCH is an autosomal dominant disorder of early onset that differs from Huntington disease in being nondementing and nonprogressive without other neurologic signs. There has been controversy regarding the existence of BCH as a discrete disorder.BACKGROUND:A single kindred was recently reported with linkage of BCH to a 20.6-KcM region on chromosome 14q.METHODS:In a four-generation family with BCH, linkage was evaluated to markers in a 23-KcM region between D14S49 and D14S66 that contains the putative BCH locus.RESULTS:A multipoint nonparametric lod score of 3.01 is consistent with linkage of disease in this family to the 14q BCH locus. A recombination event in one affected individual enabled the critical region to be narrowed to 6.93 KcM flanked by D14S1068 and D14S1064. This region contains two candidate genes: glial maturation factor beta and guanosine triphosphate cyclohydrolase 1 (GCH1). Survival motor neuron (SMN) interacting protein-1 is eliminated as a candidate gene because it lies outside the critical region. No sequence alteration was identified in the coding region of GCH1 in an affected individual.CONCLUSION:These data provide further evidence that BCH is a distinct entity, narrow the location of BCH to a 6.93-KcM region on chromosome 14q, and exclude SMN interacting protein-1 as a candidate gene.