Oculomotor Apraxia Research Articles

Clinical Characteristics, Molecular Background, and Survival of Egyptian Patients With Gaucher Disease Over a 20-Year Follow-up.

This study analyzes the general disease characteristics, impact of enzyme replacement therapy (ERT), and overall survival (OS) of 156 Egyptian patients with Gaucher disease (GD) enrolled on hormone replacement from 1998 to 2017. The mean age at diagnosis was 32.46±12.68 months. Anemia was noted at diagnosis in 50%, thrombocytopenia in 30.7%, severe splenomegaly in 58.7%, severe hepatomegaly in 11.9%, and skeletal findings were detected in 24.3% of the patients. The most prevalent GD type was type 3 (54.5%). Twenty-two of type 3 patients had no neurological manifestations at diagnosis, and 12 developed variable central nervous system manifestations during follow-up. The most common neurological features were limited eye movements, oculomotor apraxia, and squint. Of the 60 patients for whom genotypes were obtained, homozygous L444P was the most common (n=35/60, 58.3%). Treatment with ERT (imiglucerase) revealed significant improvements in blood indices, organ volumes, and growth parameters (P<0.05). Ten (11.7%) type 3 patients did not develop any neurological manifestations under ERT over 20 years. Mortality was 16%, and the 20-year OS was 73.3%. We conclude that in Egypt, type 3 is the most prevalent phenotype of GD, and homozygous L444P is the predominant GBA genotype of GD. Early age at diagnosis and treatment with ERT over 20 years revealed significant improvements in disease manifestations, with an OS of 73.3%.

SUMOylated Senataxin functions in genome stability, RNA degradation, and stress granule disassembly, and is linked with inherited ataxia and motor neuron disease.

BackgroundSenataxin (SETX) is a DNA/RNA helicase critical for neuron survival. SETX mutations underlie two inherited neurodegenerative diseases: Ataxia with Oculomotor Apraxia type 2 (AOA2) and Amyotrophic Lateral Sclerosis type 4 (ALS4).MethodsThis review examines SETX key cellular processes and we hypothesize that SETX requires SUMO posttranslational modification to function properly.ResultsSETX is localized to distinct foci during S‐phase of the cell cycle, and these foci represent sites of DNA polymerase/RNA polymerase II (RNAP) collision, as they co‐localize with DNA damage markers 53BP1 and H2AX. At such sites, SETX directs incomplete RNA transcripts to the nuclear exosome for degradation via interaction with exosome component 9 (Exosc9), a key component of the nuclear exosome. These processes require SETX SUMOylation. SETX was also recently localized within stress granules (SGs), and found to regulate SG disassembly, a process that similarly requires SUMOylation.ConclusionSETX undergoes SUMO modification to function at S‐phase foci in cycling cells to facilitate RNA degradation. SETX may regulate similar processes in non‐dividing neurons at sites of RNAP II bidirectional self‐collision. Finally, SUMOylation of SETX appears to be required for SG disassembly. This SETX function may be crucial for neuron survival, as altered SG dynamics are linked to ALS disease pathogenesis. In addition, AOA2 point mutations have been shown to block SETX SUMOylation. Such mutations induce an ataxia phenotype indistinguishable from those with SETX null mutation, underscoring the importance of this modification.

Integrating visual search, eye movement training and reversing prism exposure in the treatment of Balint-Holmes syndrome: a single case report

ABSTRACT Objective For the first time, we administered reversing prism exposure to treat optic ataxia in a single patient with Balint-Holmes Syndrome (BHS), who also underwent specific trainings for simultanagnosia and ocular apraxia. Method and Results By an introduction and withdrawal experimental design, we observed that the active treatment periods improved patient’s visuospatial defects and functional autonomy. Conclusions We thus provided a proof of principle supporting the use of reversing prism exposure in optic ataxia within an integrated and personalized rehabilitative approach for BHS.

Neurofilament Light Chain Is a Biomarker of Neurodegeneration in Ataxia Telangiectasia

Ataxia telangiectasia (A-T) is a progressive and life-limiting disease associated with cerebellar ataxia due to progressive cerebellar degeneration. In addition to ataxia, which is described in detail, the presence of chorea, dystonia, oculomotor apraxia, athetosis, parkinsonism, and myoclonia are typical manifestations of the disease. The study aimed to evaluate the specificity and sensitivity of neurofilament light chain (NfL) as a biomarker of neurodegeneration in relation to SARA score. In this prospective trial, one visit of 42 A-T patients aged 1.3–25.6 years (mean 11.6 ± 7.3 years) was performed, in which NfL was determined from serum by ELISA. Additionally, a neurological examination of the patients was performed. Blood was collected from 19 healthy volunteers ≥ 12 years of age. We found significantly increased levels of NfL in patients with A-T compared to healthy controls (21.5 ± 3.6 pg/mL vs. 9.3 ± 0.49 pg/mL, p ≤ 0.01). There was a significant correlation of NfL with age, AFP, and SARA. NfL is a new potential progression biomarker in blood for neurodegeneration in A-T which increases with age.

Posterior Cortical Atrophy phenotype in a GBA N370S mutation carrier: a case report

BackgroundGlucocerebrosidase (GBA) heterozygous variants are the most important genetic risk factor for the development of alpha-synucleinopathies (i.e., Parkinson’s disease and Dementia with Lewy Bodies). Herein, we report for the first time on a patient with a clinical diagnosis of Posterior Cortical Atrophy, carrier of the common GBA heterozygous variant N370S (c.1226A > G).Case presentationA 44-year-old woman with positive familial history for Dementia with Lewy Bodies disclosed three related signs characterizing the Balint’s syndrome: ocular apraxia, optic ataxia and simultanagnosia. Over 2-year follow up, overt gaze apraxia (psychic paralysis of gaze) appeared leading to functional blindness. Given her young age at onset and positive familial history, she underwent a next-generation-sequencing (NGS) based screening of a panel of 32 genes related to neurodegenerative conditions within the ANAMNESYS (An origiNal Approach to study faMiliarity in NEurodegenerative SYndromeS) study. NGS demonstrated the N370S variant in the GBA gene (rs76763715), confirmed by Sanger sequencing. This is a relatively common variant, with predicted mild impact, already reported to occur in 2.4% of PD Italian patients; however, neither this nor other GBA variants have ever been reported to date in patients with Posterior Cortical Atrophy. Glucocerebrosidase activity was investigated and found to be significantly reduced (4.72 nmol/h/mg) compared to healthy controls as well as patients affected by neurodegenerative diseases, further supporting pathogenicity of the GBA variant.ConclusionsWe report on a patient with a clinical diagnosis of Posterior Cortical Atrophy, carrier of the GBA heterozygous variant N370S (c.1226A > G; p.Asn409Ser) determining reduced GCase activity. This report also confirms the role of NGS-based targeted gene analysis in detecting peculiar clinical phenotypes associated with known pathogenic mutations and reinforces the knowledge that carriers of genetic variants often present phenotypic overlaps across different neurodegenerative syndromes, highlighting the limitations of current clinical diagnostic criteria in defining boundaries between distinct conditions and the difficulties of clinicians in reaching the best clinical diagnosis.

Joubert syndrome: incidence and clinicoradiological description of a genotyped series of seven cases

Joubert syndrome is produced by an alteration of the ciliary proteins essential for the structure and function of neurons and organs such as the kidneys, liver, sight, and hearing. Some 34 mutations are currently known. Calculate the incidence / prevalence, describe the phenotype / genotype and radiological alterations of this ciliopathy in our health area. We reviewed the medical records with a diagnosis of Joubert Syndrome in the last 10 years to collect phenotype, radiological characteristics, and extra-neurological manifestations in relation to the genetic alteration detected. 7 cases were included: 5 children (6 -17 years). They had 6 different mutations. Hypotonia, thin / long fingers and delayed psychomotor development were constant. They presented dysmorphic features, mental retardation, ocular apraxia, and nystagmus indistinctly in 3/7; Neonatal apnea/hyperpnea 2/7; hypoplasia of vermis 7/7; Molar syndrome was evident in 6/7 and in 2/7 there was elongation-thinning of cerebellar peduncles. Pontomesencephalic junction tightness 6/7; fastigium of the IV ventricle high in 4/7. Among the somatic complications, retinopathy 2/7, retinal coloboma 1/7, liver fibrosis 1/7, nephronoptysis 1/7 and renal cyst 1/7. The incidence of Joubert syndrome was at least 1 / 20,000 newborns / year. The pontomesencephalic and peduncular radiological alterations were constant. Hypotonia, psychomotor retardation, and thin / long fingers affected all cases.

Premature ovarian ageing following heterozygous loss of Senataxin.

Premature loss of ovarian activity before 40 years of age is known as primary ovarian insufficiency (POI) and occurs in ∼1% of women. A more subtle decline in ovarian activity, known as premature ovarian ageing (POA), occurs in ∼10% of women. Despite the high prevalence of POA, very little is known regarding its genetic causation. Senataxin (SETX) is an RNA/DNA helicase involved in repair of oxidative stress-induced DNA damage. Homozygous mutation of SETX leads to the neurodegenerative disorder, ataxia oculomotor apraxia type 2 (AOA2). There have been reports of POI in AOA2 females suggesting a link between SETX and ovarian ageing. Here, we studied female mice lacking either one (Setx+/-) or both (Setx-/-) copies of SETX over a 12- to 14-month period. We find that DNA damage is increased in oocytes from 8-month-old Setx+/- and Setx-/- females compared with Setx+/+ oocytes leading to a marked reduction in all classes of ovarian follicles at least 4 months earlier than typically occurs in female mice. Furthermore, during a 12-month long mating trial, Setx+/- and Setx-/- females produced significantly fewer pups than Setx+/+ females from 7 months of age onwards. These data show that SETX is critical for preventing POA in mice, likely by preserving DNA integrity in oocytes. Intriguingly, heterozygous Setx loss causes an equally severe impact on ovarian ageing as homozygous Setx loss. Because heterozygous SETX disruption is less likely to produce systemic effects, SETX compromise could underpin some cases of insidious POA.

Some pathogenic SETX variants are partially conserved during evolution.

Variants in SETX have been implicated in recessively and dominantly inherited disorders, ataxia with oculomotor apraxia type 2 (AOA2 OMIM# 606002) and amyotrophic lateral sclerosis (ALS4, OMIM# 602433) respectively, in humans. We report two novel bi-allelic pathogenic variants in SETX in patients suffering from ataxia with oculomotor apraxia type 2, extending the allelic spectrum of the gene variants. We also discuss the pathogenicity of SETX variants in relation to the evolutionary conservation status of the affected amino acids. Our analyses suggest that variants of some amino acids which are not fully conserved in evolution, may cause a disorder in humans, provided the particular pathogenic variant is absent in other orthologues.

Posterior cortical atrophy syndrome: Asian study

AbstractBackgroundPosterior cortical atrophy (PCA) syndrome is a rare clinical syndrome occurred in the first several years of several progressive neurodegenerative diseases, of which the manifestations are mainly confined to the impairments in the functions of posterior cerebral cortices. The underlying pathomechanisms may include Alzheimer‘s disease, Lewy body disease, corticobasal degeneration and prion disease. A consensus of the diagnostic procedures for PCA syndrome has been published in 2017, based on cases from Western countries.MethodWe invited behavioral neurologists from five Asian countries to join the study and followed the suggestions of the paper published by Scott and Crutch (2019). Each research participant investigated their cases and submitted the results to chief principal investigator. Data were analyzed and compared with those of Western countries. Moreover, a workshop was held at Tainan, Taiwan in the winter of 2019 for all investigators to reach consensus on the results.ResultA total of 63 cases (26 male) from Taiwan, Thailand, Singapore, Korea and Japan were included. Their mean age was 64.48 (SD 8.26) years, onset age 59.7 (8.37) years, and education 10.76 (5.43) years. 94.9% of the findings of brain MRI and 86.8% of the brain SPECT supported a diagnosis of PCA syndrome. As compared with the results of Crutch et al (2017), the Asian data showed more often in space perception deficits, simultanagnosia, construction dyspraxia, oculomotor apraxia, dressing apraxia, optic ataxia, alexia, left/right disorientation, acalculia, agraphia, finger agnosia, limb rigidity, onset before 65, prominent early memory disturbance, and prominent early language disturbance, while less often in hallucination. The PCA‐plus cases (n=12), as defined by 2017 consensus, were older and more in favor of Lewy body disease. Meanwhile, PCA‐plus cases had more dressing apraxia and more alexia. PCA patients with Parkinsonism had more optic ataxia, dressing apraxia, left/right disorientation, acalculia, more relative spared memory impairment and less relative spared executive dysfunction.ConclusionThe public awareness of PCA syndrome is inadequate, which may delay its timely diagnosis. The differences in clinical features between Asian and Western countries need further investigation.

Largest Cohort Study of Gaucher Disease Type 3 from a Single Center in Egypt Spanning Two Decades

Background and objectives:Gaucher disease (GD) is renowned for genotype/phenotype studies and therapeutic innovation. However, the vast majority of the literature is focused on Type 1 GD related to the founder mutation, p.Asn409Ser in GBA gene although p.Leu483Pro GBA mutation associated GD may be far more prevalent across the world. In Egypt GD represents as high as 14.7% of all reported lysosomal disorders with the neuronopathic forms. Therefore, a large single center cohort study of a highly consanguineous GD population has the potential to inform genotype/phenotype, natural history studies and illuminate unmet needs. Methods:At University of Cairo's Pediatric Hematology Clinic since 1998, we have managed a total of 156 patients with GD with longitudinal data captured under an approved IRB protocol. In the present study, we focused analysis on 85 patients in whom we had long-term outcome after 20 years of enzyme replacement therapy (ERT). GBA gene analysis was performed by whole exome sequencing of DNA isolated from dry blood spots. Data on the clinical phenotype indicators at baseline and during ERT were collected including liver and spleen volumes, growth parameters, bone status, neurological assessment and eye movement. SPSS (Statistical Package for the Social Sciences) version 24 was used to compile data, assess significance and survival by Kaplan Meier analysis. Overall survival (OS) is defined as date of diagnosis till date of death, patients alive or lost during follow up was considered censored till the last date of follow up. Results:The median age at diagnosis was 1 year (IQR: 0.08-15 years) with majority (64.7%) diagnosed in first 2 years of life (range 0.5-2 yrs). The patient population was highly consanguineous and 51% of the patients reported positive family history of GD. The most prevalent genotype (75% of patients) was p.Leu483Pro homozygous. Homozygosity for p.Asp448His was present in 11% of patients. Other GBA mutations included: p.Leu483Pro homozygous in 3 patients, one heteroallelic with p.Leu483Pro; pArg87Trp homozygous in 2 patients; p.Arg398Gln homozygous in one patient). Hematological features of patients at diagnosis revealed anemia in 76% and thrombocytopenia in 22%. Massive splenomegaly (˃15 Multiples of Normal by ultrasonography) was present in 49%, 4 patients were splenectomised, hepatomegaly (˃2.5 MN) in 11%, liver cirrhosis with hepatopulmonary syndrome in one patient. Skeletal findings included multiple fractures in 3 patients and kyphosis in 3 patients. The most common neurological findings were oculomotor apraxia, squint and bulbar symptoms (48%, 30.6% and 29.4% respectively). Bone marrow examination showed Gaucher cell infiltration in 76% of the patients. Patients received Imiglucerase (Cerezyme) dose individualized by baseline disease severity. Debilitating and potentially life-threatening visceral and hematologic disease was reversed with ERT (table 1). One splenectomized patient with massive hepatomegaly and hepatopulmonary syndrome showed complete reversal on high dose ERT. Preliminary observer reported outcomes (by clinician and parent) with respect to neurological findings including oculomotor apraxia appeared to show mild improvement. Follow-up of 10 patients in whom ERT was initiated early had striking overall outcomes progressing through school and university. At 20 years, the overall survival was 71%; 20 patients died from disease complications mostly pulmonary and progressive neurological disease. Comparison of the OS in relation to gender, age at diagnosis, severity of hematological and visceral parameters showed that none of the studied variables affects OS (p˃0.05) (fig. 1). Conclusion:This study represents the largest and most extensive single-center cohort of GD3 patients with predominant p.Leu483Pro homozygous GBA genotype, without presence of a complex allele. Patients had uniformly very early-onset disease before age 2 years with devastating hematological and visceral disease which was effectively reversed by ERT. During 20 year-follow up of the cohort, there was striking reversal of hematovisceral disease and about a third of the patients succumbed to complications of GD3. OS was not correlated with severity of baseline disease underscoring the potential role of modifier genes. Disclosures No relevant conflicts of interest to declare.

Asymmetric Bálint’s syndrome with multimodal agnosia, bilateral agraphesthesia, and ineffective kinesthetic reading due to subcortical hemorrhage in the left parieto-occipito-temporal area

ABSTRACT We report a patient with asymmetric Bálint’s syndrome (predominantly right-sided oculomotor apraxia and simultanagnosia and optic ataxia for the right hemispace), and multimodal agnosia (apperceptive visual agnosia and bilateral associative tactile agnosia) with accompanying right hemianopia, bilateral agraphesthesia, hemispatial neglect, global alexia with unavailable kinesthetic reading, and lexical agraphia for kanji (Japanese morphograms), after hemorrhage in the left parieto-occipito-temporal area. The coexistence of tactile agnosia, bilateral agraphesthesia, and ineffective kinesthetic reading suggests that tactile-kinesthetic information can be interrupted because of damage to the fiber connection from the parietal lobe to the occipito-temporal area, leading to these tactually related cognitive impairments.

Autosomal Recessive Cerebellar Ataxias With Elevated Alpha-Fetoprotein: Uncommon Diseases, Common Biomarker.

alpha-Fetoprotein (AFP) is a biomarker of several autosomal recessive cerebellar ataxias (ARCAs), especially ataxia telangiectasia (AT) and ataxia with oculomotor apraxia (AOA) type 2 (AOA2). More recently, slightly elevated AFP has been reported in AOA1 and AOA4. Interestingly, AOA1, AOA2, AOA4, and AT are overlapping ARCAs characterized by oculomotor apraxia, with oculocephalic dissociation, choreo-dystonia, and/or axonal sensorimotor neuropathy, in addition to cerebellar ataxia with cerebellar atrophy. The genetic backgrounds in these disorders play central roles in nuclear maintenance through DNA repair [ATM (AT), APTX (AOA1), or PNKP (AOA4)] or RNA termination [SETX (AOA2)]. Partially discriminating thresholds of AFP have been proposed as a way to distinguish between ARCAs with elevated AFP. In these entities, elevated AFP may be an epiphenomenon as a result of liver transcriptional dysregulation. AFP is a simple and reliable biomarker for the diagnosis of ARCA in performance and interpretation of next-generation sequencing. Here, we evaluated clinical, laboratory, imaging, and molecular data of the group of ARCAs that share elevated AFP serum levels that have been described in the past two decades. © 2020 International Parkinson and Movement Disorder Society.

Clinical characteristics of ataxia-telangiectasia presenting dystonia as a main manifestation

IntroductionBesides cerebellar ataxia, various other movement disorders, including dystonia, could manifest as main clinical symptoms in ataxia-telangiectasia (A–T). However, the clinical characteristics of dystonic A–T patients are not clearly elucidated. MethodsTo investigate the characteristics of dystonic A–T, we screened previous reports with A–T patients presenting dystonia as a main manifestation, and included 38 dystonic A–T patients from 16 previous studies and our 2 cases. We reviewed clinical and demographic data of dystonic A–T patients. Additionally, to figure out clinical meaning of cerebellar involvement in dystonic A–T, we divided them into two groups based on the presence of cerebellar involvement, and compared clinical features between two groups. ResultsIn the patients with dystonic A–T, dystonia tended to appear during childhood or adolescence and became generalized over time. Choreoathetosis and myoclonus accompanied more frequently than the typical clinical features, including cerebellar ataxia or atrophy, telangiectasia, or oculomotor apraxia. Additionally, alpha-fetoprotein level was also elevated in the patients with dystonic A–T. When we compared dystonic A–T with and without cerebellar involvement, the former was related with more chance for telangiectasia and oculomotor apraxia, while the latter with that for choreoathetosis and malignancy. ConclusionEven without ataxia, telangiectasia, or oculomotor apraxia, A–T should be considered in undiagnosed dystonia, especially generalized dystonia which started from childhood or adolescence period, and alpha-fetoprotein level can be a useful screening tool. In addition, cerebellar involvement is important considering different phenotype in dystonic A–T patients with and without cerebellar sign.

Senataxin gene mutation presenting with ataxia oculomotor apraxia type 2: Five patients with three different mutations

Background and Aims: Autosomal recessive cerebellar ataxias constitute a highly heterogeneous group of neurodegenerative disorders. Ataxia oculomotor apraxia type 2 (AOAT 2) is a disorder with senataxin (SETX) gene mutation causing usually juvenile and adult onset cerebellar ataxia. We present patients with AOAT 2 in five different families with SETX gene mutations which two of them novel mutations.

Linker region is required for efficient nuclear localization of polynucleotide kinase phosphatase.

Polynucleotide kinase phosphatase (PNKP) is a DNA repair factor with dual enzymatic functions, i.e., phosphorylation of 5’-end and dephosphorylation of 3’-end, which are prerequisites for DNA ligation and, thus, is involved in multiple DNA repair pathways, i.e., base excision repair, single-strand break repair and double-strand break repair through non-homologous end joining. Mutations in PNKP gene causes inherited diseases, such as microcephaly and seizure (MCSZ) by neural developmental failure and ataxia with oculomotor apraxia 4 (AOA4) and Charcot-Marie-Tooth disease 2B2 (CMT2B2) by neurodegeneration. PNKP consists of the Forkhead-associated (FHA) domain, linker region, phosphatase domain and kinase domain. Although the functional importance of PNKP interaction with XRCC1 and XRCC4 through the FHA domain and that of phosphatase and kinase enzyme activities have been well established, little is known about the function of linker region. In this study, we identified a functional putative nuclear localization signal (NLS) of PNKP located in the linker region, and showed that lysine 138 (K138), arginine 139 (R139) and arginine 141 (R141) residues therein are critically important for nuclear localization. Furthermore, double mutant of K138A and R35A, the latter of which mutates arginine 35, central amino acid of FHA domain, showed additive effect on nuclear localization, indicating that the FHA domain as well as the NLS is important for PNKP nuclear localization. Thus, this study revealed two distinct mechanisms regulating nuclear localization and subnuclear distribution of PNKP. These findings would contribute to deeper understanding of a variety of DNA repair pathway, i.e., base excision repair, single-strand break repair and double-strand break repair.

SETX (senataxin), the helicase mutated in AOA2 and ALS4, functions in autophagy regulation

ABSTRACT SETX (senataxin) is an RNA/DNA helicase that has been implicated in transcriptional regulation and the DNA damage response through resolution of R-loop structures. Mutations in SETX result in either of two distinct neurodegenerative disorders. SETX dominant mutations result in a juvenile form of amyotrophic lateral sclerosis (ALS) called ALS4, whereas recessive mutations are responsible for ataxia called ataxia with oculomotor apraxia type 2 (AOA2). How mutations in the same protein can lead to different phenotypes is still unclear. To elucidate AOA2 disease mechanisms, we first examined gene expression changes following SETX depletion. We observed the effects on both transcription and RNA processing, but surprisingly observed decreased R-loop accumulation in SETX-depleted cells. Importantly, we discovered a strong connection between SETX and the macroautophagy/autophagy pathway, reflecting a direct effect on transcription of autophagy genes. We show that SETX depletion inhibits the progression of autophagy, leading to an accumulation of ubiquitinated proteins, decreased ability to clear protein aggregates, as well as mitochondrial defects. Analysis of AOA2 patient fibroblasts also revealed a perturbation of the autophagy pathway. Our work has thus identified a novel function for SETX in the regulation of autophagy, whose modulation may have a therapeutic impact for AOA2. Abbreviations: 3ʹREADS: 3ʹ region extraction and deep sequencing; ACTB: actin beta; ALS4: amyotrophic lateral sclerosis type 4; AOA2: ataxia with oculomotor apraxia type 2; APA: alternative polyadenylation; AS: alternative splicing; ATG7: autophagy-related 7; ATP6V0D2: ATPase H+ transporting V0 subunit D2; BAF: bafilomycin A1; BECN1: beclin 1; ChIP: chromatin IP; Chloro: chloroquine; CPT: camptothecin; DDR: DNA damage response; DNMT1: DNA methyltransferase 1; DRIP: DNA/RNA IP; DSBs: double strand breaks; EBs: embryoid bodies; FTD: frontotemporal dementia; GABARAP: GABA type A receptor-associated protein; GO: gene ontology; HR: homologous recombination; HTT: huntingtin; IF: immunofluorescence; IP: immunoprecipitation; iPSCs: induced pluripotent stem cells; KD: knockdown; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MN: motor neuron; MTORC1: mechanistic target of rapamycin kinase complex 1; PASS: PolyA Site Supporting; PFA: paraformaldehyde; RNAPII: RNA polymerase II; SCA: spinocerebellar ataxia; SETX: senataxin; SMA: spinal muscular atrophy; SMN1: survival of motor neuron 1, telomeric; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; TSS: transcription start site; TTS: transcription termination site; ULK1: unc-51 like autophagy activating kinase 1; WB: western blot; WIPI2: WD repeat domain, phosphoinositide interacting 2; XRN2: 5ʹ-3ʹ exoribonuclease 2.

Identification of APTX disease-causing mutation in two unrelated Jordanian families with cerebellar ataxia and sensitivity to DNA damaging agents

Ataxia with oculomotor apraxia type 1 (AOA1) is a rare autosomal recessive cerebellar ataxia, caused by mutations in the APTX gene. The disease is characterized by early-onset cerebellar ataxia, oculomotor apraxia and severe axonal polyneuropathy. The aim of this study was to detect the disease-causing variants in two unrelated consanguineous Jordanian families with cerebellar ataxia using whole exome sequencing (WES), and to correlate the identified mutation(s) with the clinical and cellular phenotypes. WES was performed in three affected individuals and segregation analysis of p.W279* APTX candidate variant was performed. Expression levels of APTX were measured in patients' skin fibroblasts and peripheral blood mononuclear cells, followed by western blot analysis in skin fibroblasts. Genotoxicity assay was performed to detect the sensitivity of APTX mutated cells to H2O2, MMC, MMS and etoposide. A recurrent homozygous nonsense variant in APTX gene (c.837G>A, p.W279*) was revealed in all affected individuals. qRT-PCR showed normal APTX levels in peripheral blood and lower levels in fibroblast cells. However, western blot showed the absence of APTX protein in patients' skin fibroblasts. Significant hypersensitivity to H2O2, MMC and etoposide and lack of sensitivity to MMS were noted. This is the first study to report the identification of a nonsense variant in the APTX gene (c.837G>A; p.W279*) in AOA1 patients within the Jordanian population. This study confirmed the need of WES to assist in the diagnosis of cerebellar ataxia and it emphasizes the importance of studying the pathophysiology of the APTX gene.

The Phenotypic Spectrum of PNKP-Associated Disease and the Absence of Immunodeficiency and Cancer Predisposition in a Dutch Cohort

BackgroundWe aimed to expand the number of currently known pathogenic PNKP mutations, to study the phenotypic spectrum, including radiological characteristics and genotype-phenotype correlations, and to assess whether immunodeficiency and increased cancer risk are part of the DNA repair disorder caused by mutations in the PNKP gene. MethodsWe evaluated nine patients with PNKP mutations. A neurological history and examination was obtained. All patients had undergone neuroimaging and genetic testing as part of the prior diagnostic process. Laboratory measurements included potential biomarkers, and, in the context of a DNA repair disorder, we performed a detailed immunologic evaluation, including B cell repertoire analysis. ResultsWe identified three new mutations in the PNKP gene and confirm the phenotypic spectrum of PNKP-associated disease, ranging from microcephaly, seizures, and developmental delay to ataxia with oculomotor apraxia type 4. Irrespective of the phenotype, alpha-fetoprotein is a biochemical marker and increases with age and progression of the disease. On neuroimaging, (progressive) cerebellar atrophy was a universal feature. No clinical signs of immunodeficiency were present, and immunologic assessment was unremarkable. One patient developed cancer, but this was attributed to a concurrent von Hippel-Lindau mutation. ConclusionsImmunodeficiency and cancer predisposition do not appear to be part of PNKP-associated disease, contrasting many other DNA repair disorders. Furthermore, our study illustrates that the previously described syndromes microcephaly, seizures, and developmental delay, and ataxia with oculomotor apraxia type 4, represent the extremes of an overlapping spectrum of disease. Cerebellar atrophy and elevated serum alpha-fetoprotein levels are early diagnostic findings across the entire phenotypical spectrum.

Generation and characterization of induced pluripotent stem cell (iPSC) line (JUCTCi002-A) from a patient with ataxia with oculomotor apraxia type 1 (AOA1) harboring a homozygous mutation in the APTX gene.

Ataxia with Oculomotor Apraxia Type 1 (AOA1) is an autosomal-recessive cerebellar ataxia characterized by early-onset cerebellar atrophy and axonal sensorimotor polyneuropathy. AOA1 is related to mutations in the aprataxin (APTX) gene encoding for the aprataxin protein. The aprataxin protein has been reported to be involved in DNA single-strand break repair (SSBR) machinery and it localizes to the mitochondria to preserve the mitochondrial function. Here, we demonstrate the generation of induced pluripotent stem cell (iPSC) line (JUCTCi002-A) from AOA1 patient's skin dermal fibroblasts. The selected line showed normal karyotype, expression of pluripotency markers and the ability to differentiatie in vitro into the three germ layers.

Ataxia with Impaired DNA Repair in Adults: A Case Series and Review of the Literature

Introduction . Ataxia with impaired DNA repair is a group of inherited diseases with a wide range of neurological and extraneural manifestations. There are some difficulties in the differential diagnosis of this group of ataxias due to significant clinical polymorphism. Objective . To analyze the clinical presentation, laboratory and instrumental examinations data of a series of genetically confirmed cases of ataxia with impaired DNA repair in adult patients. Material and methods . 55 patients with ataxia of degenerative origin were examined. Clinical evaluation, nerve velocity study, brain MRI, alpha-fetoprotein, immunoglobulins, cholesterol and albumin, creatine phosphokinase activity were performed. Massive parallel sequencing (MPS) was used for genotyping, including the original multigene panel. Results . 8 (14.5%) patients with various forms of ataxia with impaired DNA repair were verified: 5 patients with ataxia-telangiectasia, 3 — with ataxia with oculomotor apraxia types 1 and 2. The clinical features of this forms are characterized, the prevalence of atypical forms of ataxia-telangiectasia in a sample of Russian adult patients is revealed. Phenotypes of ataxia with oculomotor apraxia of the 1 and 2 types corresponded to the classical presentation. Several identified mutations in the ATM and SETX genes are described for the first time. Conclusion . Ataxia with impaired DNA repair is a common group of ataxias in adult Russian patients. They are represented by ataxia-telangiectasia, ataxia with oculomotor apraxia types 1 and 2, often due to new mutations. MPS is the method of choice for genotyping of these forms of ataxia.