[Clinical features and genetic analysis of a patient with type 2 neurofibromatosis manifested as oculomotor nerve palsy].

OBJECTIVE: To report on a rare case of Neurofibromatosis type 2 (NF2) manifesting as oculomotor nerve palsy and explore its genetic basis. METHODS: A patient with NF2 who had presented at Beijing Ditan Hospital Affiliated to Capital Medical University on July 10, 2021 was selected as the study subject. Cranial and spinal cord magnetic resonance imaging (MRI) was carried out on the patient and his parents. Peripheral blood samples were collected and subjected to whole exome sequencing. Candidate variant was verified by Sanger sequencing. RESULTS: MRI revealed bilateral vestibular Schwannomas, bilateral cavernous sinus meningiomas, popliteal neurogenic tumors, and multiple subcutaneous nodules in the patient. DNA sequencing revealed that he has harbored a de novo nonsense variant of the NF2 gene, namely c.757A>T, which has replaced a codon (AAG) encoding lysine (K) at position 253 with a stop codon (TAG). This has resulted in removal of the Merlin protein encoded by the NF2 gene from position 253 onwards. The variant was not found in public databases. Bioinformatic analysis suggested that the corresponding amino acid is highly conserved. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was rated as pathogenic (PVS1+PS2+PM2_Supporting+PP3+PP4). CONCLUSION: The heterozygous nonsense variant c.757A>T (p.K253*) of the NF2 gene probably underlay the disease in this patient with an early onset, atypical but severe phenotype.

[ADA2 deficit: a case with neurological manifestations as a predominant clinic]. / Déficit de ADA2: caso con manifestaciones neurológicas como clínica predominante.

TITLE: Déficit de ADA2: caso con manifestaciones neurológicas como clínica predominante.

Recessive mutations in COL25A1 are a cause of congenital cranial dysinnervation disorder.

Abnormal ocular motility is a common clinical feature in congenital cranial dysinnervation disorder (CCDD). To date, eight genes related to neuronal development have been associated with different CCDD phenotypes. By using linkage analysis, candidate gene screening, and exome sequencing, we identified three mutations in collagen, type XXV, alpha 1 (COL25A1) in individuals with autosomal-recessive inheritance of CCDD ophthalmic phenotypes. These mutations affected either stability or levels of the protein. We further detected altered levels of sAPP (neuronal protein involved in axon guidance and synaptogenesis) and TUBB3 (encoded by TUBB3, which is mutated in CFEOM3) as a result of null mutations in COL25A1. Our data suggest that lack of COL25A1 might interfere with molecular pathways involved in oculomotor neuron development, leading to CCDD phenotypes.

Cognitive impairment in native Chinese with spinocerebellar ataxia type 3.

BACKGROUND: Previous studies have shown cognitive impairment in patients with spinocerebellar ataxia type 3 (SCA3). However, there is a lack of data on Chinese patients with SCA3. METHOD: We investigated 22 native Chinese with SCA3 and 18 controls matched for age, education as well as mental status. Cognitive assessments were carefully carried out to measure verbal fluency, memory, attention, executive function, visuospatial and visuoconstructive functions. RESULTS: The most common impairments of cognition in native Chinese with SCA3 were disruption of phonemic verbal fluency and frontal executive dysfunction. Deficits in semantic fluency were detected in about 31.8% patients. Impaired visuospatial function and verbal memory were also found in native Chinese with SCA3. The degree of ataxia, CAG repeat length and education were found to correlate with cognitive performance. Multivariate binary logistic regression suggested that an oculomotor disorder and depression are predictors of cognitive impairment. CONCLUSION: Native Chinese with SCA3 had cognitive impairment of frontal executive function, temporal and parietal functions. An oculomotor disorder might be an index of cognitive dysfunction.

A decade of proteomics studies of glaucomatous neurodegeneration.

Glaucoma is a leading cause of blindness; however, limited understanding of the molecular mechanisms involved in optic nerve degeneration hinders the development of improved treatment strategies. Proteomics techniques that combine the protein chemistry, MS, and bioinformatics offer the opportunity to shed light on molecular mechanisms so that new treatment strategies can be developed for immunomodulation, neuroprotection, neurorescue, neuroregeneration, and function gain in glaucoma. The proteomics technologies also hold great promise for biomarker discovery, another important goal of glaucoma research. As much as developing new treatment strategies, molecular biomarkers are strongly needed for early diagnosis of glaucoma, prediction of its prognosis, and monitoring the responses to new treatments. It is now a decade that the proteomics analysis techniques have been using to move glaucoma research forward. This review will focus on valuable applications of proteomics in the field of glaucoma research and highlight the power of this analytical toolbox in translational and clinical research toward better characterization and improved treatment of glaucomatous neurodegeneration and discovery of glaucoma-related molecular biomarkers.

Oculomotor deficits in aryl hydrocarbon receptor null mouse.

The Aryl hydrocarbon Receptor or AhR, a ligand-activated transcription factor, is known to mediate the toxic and carcinogenic effects of various environmental pollutants such as 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD). Recent studies in Caenorhabditis elegans and Drosophila melanogaster show that the orthologs of the AhR are expressed exclusively in certain types of neurons and are implicated in the development and the homeostasis of the central nervous system. While physiological roles of the AhR were demonstrated in the mammalian heart, liver and gametogenesis, its ontogenic expression and putative neural functions remain elusive. Here, we report that the constitutive absence of the AhR in adult mice (AhR-/-) leads to abnormal eye movements in the form of a spontaneous pendular horizontal nystagmus. To determine if the nystagmus is of vestibular, visual, or cerebellar origin, gaze stabilizing reflexes, namely vestibulo-ocular and optokinetic reflexes (VOR and OKR), were investigated. The OKR is less effective in the AhR-/- mice suggesting a deficit in the visuo-motor circuitry, while the VOR is mildly affected. Furthermore, the AhR is expressed in the retinal ganglion cells during the development, however electroretinograms revealed no impairment of retinal cell function. The structure of the cerebellum of the AhR-/- mice is normal which is compatible with the preserved VOR adaptation, a plastic process dependent on cerebellar integrity. Finally, intoxication with TCDD of control adults did not lead to any abnormality of the oculomotor control. These results demonstrate that the absence of the AhR leads to acquired central nervous system deficits in the adults. Given the many common features between both AhR mouse and human infantile nystagmus syndromes, the AhR-/- mice might give insights into the developmental mechanisms which lead to congenital eye disorders.

Slowly progressive ataxia, neuropathy, and oculomotor dysfunction.

A 54-year-old white man presented with slowly progressive incoordination and weakness. He had normal motor development until, at 16 years of age, he noted difficulty walking and difficulty reading despite normal visual acuity. By the fourth decade of life, he developed poor coordination and balance, as well as inability to walk. In subsequent years, he developed progressive, painless sensory loss, weakness, and atrophy in his distal arms and legs. His vision problems progressed and he also developed dysarthria without dysphagia. Family history was negative except for an uncle who was described as "clumsy." Results of an oculomotor examination were notable for increased square-wave jerks, persistent bilateral gaze-evoked nystagmus with saccadic pursuit, intact vestibulo-ocular reflex, and saccadic dysmetria. He had a mixed dysarthria with flaccid and ataxic characteristics and severe weakness and atrophy in the distal limb muscles. Sensation was diminished to the midforearms and midthighs in all modalities. Deep tendon reflexes were absent throughout, with no response to plantar stimulation. He had marked appendicular ataxia with mild axial ataxia. Magnetic resonance imaging of the brain revealed severe cerebellar atrophy. Results of an electrodiagnostic study suggested a severe axonal sensorimotor polyneuropathy with active and chronic denervation. The differential diagnosis in a patient with ataxia, neuropathy, and oculomotor features is discussed; a methodical approach to the diagnostic workup is suggested; and the final diagnosis is revealed.

Horizontal gaze palsy and progressive scoliosis due to a deleterious mutation in ROBO3.

PURPOSE: To describe a family with horizontal gaze palsy and progressive scoliosis with a deleterious mutation in the ROBO3 gene. METHODS: All family members had full ophthalmologic, neurologic, and orthopedic examinations and complete sequencing of the ROBO3 gene. RESULTS: Four affected members had complete loss of horizontal gaze with progressive scoliosis that varied between family members. ROBO3 sequencing revealed a novel 15 base deletion (c.2_16 delTGCTGCGCTACCTGC) in exon 1 that segregated in homozygous form with the phenotype and probably alters the shape and ionic charge of the extracellular immunoglobulin motif 1. This mutation was not detected in 100 control chromosomes. CONCLUSIONS: The novel ROBO3 mutation in this family may be among the most deleterious yet reported. Family members in general were severely affected, but comparison of this family to other families with ROBO3 mutations did not yield a definitive phenotype-genotype correlation.

Ataxia with oculomotor apraxia type1 (AOA1): novel and recurrent aprataxin mutations, coenzyme Q10 analyses, and clinical findings in Italian patients.

Ataxia with oculomotor apraxia type1 (AOA1, MIM 208920) is a rare autosomal recessive disease caused by mutations in the APTX gene. We screened a cohort of 204 patients with cerebellar ataxia and 52 patients with early-onset isolated chorea. APTX gene mutations were found in 13 ataxic patients (6%). Eleven patients were homozygous for the known p.W279X, p.W279R, and p.P206L mutations. Three novel APTX mutations were identified: c.477delC (p.I159fsX171), c.C541T (p.Q181X), and c.C916T (p.R306X). Expression of mutated proteins in lymphocytes from these patients was greatly decreased. No mutations were identified in subjects with isolated chorea. Two heterozygous APTX sequence variants (p.L248M and p.D185E) were found in six families with ataxic phenotype. Analyses of coenzyme Q10 in muscle, fibroblasts, and plasma demonstrated normal levels of coenzyme in five of six mutated subjects. The clinical phenotype was homogeneous, irrespectively of the type and location of the APTX mutation, and it was mainly characterized by early-onset cerebellar signs, sensory neuropathy, cognitive decline, and oculomotor deficits. Three cases had slightly raised alpha-fetoprotein. Our survey describes one of the largest series of AOA1 patients and contributes in defining clinical, molecular, and biochemical characteristics of this rare hereditary neurological condition.

Molecular diagnosis of known recessive ataxias by homozygosity mapping with SNP arrays.

The diagnosis of rare inherited diseases is becoming more and more complex as an increasing number of clinical conditions appear to be genetically heterogeneous. Multigenic inheritance also applies to the autosomal recessive progressive cerebellar ataxias (ARCAs), for which 14 genes have been identified and more are expected to be discovered. We used homozygosity mapping as a guide for identification of the defective locus in patients with ARCA born from consanguineous parents. Patients from 97 families were analyzed with GeneChip Mapping 10K or 50K SNP Affymetrix microarrays. We identified six families homozygous for regions containing the autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) gene, two families homozygous for the ataxia-telangiectasia gene (ATM), two families homozygous for the ataxia with oculomotor apraxia type 1 (AOA1) gene, and one family homozygous for the AOA type 2 (AOA2) gene. Upon direct gene testing, we were able to identify a disease-related mutation in all families but one of the two kindred homozygous at the ATM locus. Although linkage analyses pointed to a single locus on chromosome 11q22.1-q23.1 for this family, clinical features, normal levels of serum alpha-foetoprotein as well as absence of mutations in the ATM gene rather suggest the existence of an additional ARCA-related gene in that interval. While the use of homozygosity mapping was very effective at pointing to the correct gene, it also suggests that the majority of patients harbor mutations either in the genes of the rare forms of ARCA or in genes yet to be identified.

Ophthalmologic features of the common spinocerebellar ataxias.

PURPOSE OF REVIEW: The spinocerebellar ataxias (SCAs) are a phenotypically and genetically diverse group of autosomal dominant disorders that cause pathological degeneration in the cerebellum, brainstem, and retina, resulting in a wide variety of ophthalmologic signs and symptoms. RECENT FINDINGS: The genetic discrimination of the SCAs has advanced dramatically over the past decade. The most common genetic (mutational) mechanism for the SCAs is an abnormal expansion to a stretch of glutamine amino acid residues (polyglutamine tract) encoded by any of several SCA-causing genes. Knowledge regarding the pathophysiology of polyglutamine-expansion-induced protein dysfunction is an area of intense investigation. SUMMARY: The ophthalmologist may be the first to encounter a patient with SCA, and a review of the most common genetic subtypes of this disorder is helpful in diagnosis and management.

Evidence of an asymmetrical endophenotype in congenital fibrosis of extraocular muscles type 3 resulting from TUBB3 mutations.

PURPOSE: Orbital magnetic resonance imaging (MRI) was used to investigate the structural basis of motility abnormalities in congenital fibrosis of the extraocular muscles type 3 (CFEOM3), a disorder resulting from missense mutations in TUBB3, which encodes neuron-specific beta-tubulin isotype III. METHODS: Ophthalmic examinations in 13 volunteers from four CFEOM3 pedigrees and normal control subjects, were correlated with TUBB3 mutation and MRI findings that demonstrated extraocular muscle (EOM) size, location, contractility, and innervation. RESULTS: Volunteers included clinically affected and clinically unaffected carriers of R262C and D417N TUBB3 amino acid substitutions and one unaffected, mutation-negative family member. Subjects with CFEOM3 frequently had asymmetrical blepharoptosis, limited vertical duction, variable ophthalmoplegia, exotropia, and paradoxical abduction in infraduction. MRI demonstrated variable, asymmetrical levator palpebrae superioris and superior rectus EOM atrophy that correlated with blepharoptosis, deficient supraduction, and small orbital motor nerves. Additional EOMs exhibited variable hypoplasia that correlated with duction deficit, but the superior oblique muscle was spared. Ophthalmoplegia occurred only when the subarachnoid width of CN3 was <1.9 mm. A-pattern exotropia was frequent, correlating with apparent lateral rectus (LR) muscle misinnervation by CN3. Optic nerve (ON) cross sections were subnormal, but rectus pulley locations were normal. CONCLUSIONS: CFEOM3 caused by TUBB3 R262C and D417N amino acid substitutions features abnormalities of EOM innervation and function that correlate with subarachnoid CN3 hypoplasia, occasional abducens nerve hypoplasia, and subclinical ON hypoplasia that can resemble CFEOM1. Clinical and MRI findings in CFEOM3 are more variable than those in CFEOM1 and are often asymmetrical. Apparent LR innervation by the inferior rectus motor nerve is an overlapping feature of Duane retraction syndrome and CFEOM1. These findings suggest that CFEOM3 is an asymmetrical, variably penetrant, congenital cranial dysinnervation disorder leading to secondary EOM atrophy.

Exon deletions and intragenic insertions are not rare in ataxia with oculomotor apraxia 2.

BACKGROUND: The autosomal recessively inherited ataxia with oculomotor apraxia 2 (AOA2) is a neurodegenerative disorder characterized by juvenile or adolescent age of onset, gait ataxia, cerebellar atrophy, axonal sensorimotor neuropathy, oculomotor apraxia, and elevated serum AFP levels. AOA2 is caused by mutations within the senataxin gene (SETX). The majority of known mutations are nonsense, missense, and splice site mutations, as well as small deletions and insertions. METHODS: To detect mutations in patients showing a clinical phenotype consistent with AOA2, the coding region including splice sites of the SETX gene was sequenced and dosage analyses for all exons were performed on genomic DNA. The sequence of cDNA fragments of alternative transcripts isolated after RT-PCR was determined. RESULTS: Sequence analyses of the SETX gene in four patients revealed a heterozygous nonsense mutation or a 4 bp deletion in three cases. In another patient, PCR amplification of exon 11 to 15 dropped out. Dosage analyses and breakpoint localisation yielded a 1.3 kb LINE1 insertion in exon 12 (patient P1) and a 6.1 kb deletion between intron 11 and intron 14 (patient P2) in addition to the heterozygous nonsense mutation R1606X. Patient P3 was compound heterozygous for a 4 bp deletion in exon 10 and a 20.7 kb deletion between intron 10 and 15. This deletion was present in a homozygous state in patient P4. CONCLUSION: Our findings indicate that gross mutations seem to be a frequent cause of AOA2 and reveal the importance of additional copy number analysis for routine diagnostics.

Functional role for senataxin, defective in ataxia oculomotor apraxia type 2, in transcriptional regulation.

Ataxia oculomotor apraxia type 2 (AOA2) is an autosomal recessive neurodegenerative disorder characterized by cerebellar ataxia and oculomotor apraxia. The gene mutated in AOA2, SETX, encodes senataxin, a putative DNA/RNA helicase which shares high homology to the yeast Sen1p protein and has been shown to play a role in the response to oxidative stress. To investigate further the function of senataxin, we identified novel senataxin-interacting proteins, the majority of which are involved in transcription and RNA processing, including RNA polymerase II. Binding of RNA polymerase II to candidate genes was significantly reduced in senataxin deficient cells and this was accompanied by decreased transcription of these genes, suggesting a role for senataxin in the regulation/modulation of transcription. RNA polymerase II-dependent transcription termination was defective in cells depleted of senataxin in keeping with the observed interaction of senataxin with poly(A) binding proteins 1 and 2. Splicing efficiency of specific mRNAs and alternate splice-site selection of both endogenous genes and artificial minigenes were altered in senataxin depleted cells. These data suggest that senataxin, similar to its yeast homolog Sen1p, plays a role in coordinating transcriptional events, in addition to its role in DNA repair.

MRI findings in Joubert syndrome.

Joubert syndrome is a very rare autosomal recessive disorder with only 200 cases reported worldwide.Here we report 4 cases of this rare disorder with MRI findings.

Five new consanguineous families with horizontal gaze palsy and progressive scoliosis and novel ROBO3 mutations.

Horizontal gaze palsy and progressive scoliosis (HGPPS) is an autosomal recessive neurologic disorder caused by homozygous or compound heterozygous mutations in the ROBO3 gene on chromosome 11. We clinically evaluated seven individuals with HGPPS from five previously unreported consanguineous families. We sequenced ROBO3 in all affected individuals, additional unaffected members of each family, and ethnic controls. All affected individuals had severe horizontal gaze restriction, progressive scoliosis, and lower brainstem hypoplasia on neuroimaging, the hallmarks of this syndrome. One individual experienced head trauma with a right subdural hematoma associated with a right hemiparesis, observations that confirm clinically for the first time that corticospinal tracts in HGPPS are uncrossed. We found five novel homozygous ROBO3 mutations (four missense mutations and one base deletion) distributed throughout the extracellular domain of the gene. The ROBO3 gene does not appear to have an obvious hot spot area for mutations; therefore, we recommend sequencing all exons and exon-intron boundaries in patients with clinical and/or radiologic features of HGPPS.

Ataxia with oculomotor apraxia.

Ataxia-telangiectasia (AT) belongs to a group of recessively inherited disorders characterized by progressive ataxia and oculomotor apraxia. Included in this group are AT, ataxia-telangiectasia-like disorder (ATLD), ataxia with oculomotor apraxia type 1 (AOA 1), ataxia with oculomotor apraxia type 2 (AOA 2), and the recently described AOA3. Common to this group is the underlying cellular defect in the recognition and repair of double-strand or single-strand DNA breaks. Clinical and laboratory features allow one to distinguish between these various disorders. In this report, we describe a child with early onset progressive ataxia, oculomotor apraxia, ocular telangiectasia, and white-matter changes by magnetic resonance imaging, which appears to be yet another novel form of AOA. We designate this condition as AOA-WM to call attention to the central demyelination seen in this variety of ataxia with oculomotor apraxia.

Clinical and molecular findings of ataxia with oculomotor apraxia type 2 in 4 families.

BACKGROUND: Ataxia with oculomotor apraxia type 2 (AOA2) is an autosomal recessive disease caused by SETX mutations in 9q34 resulting in cerebellar ataxia in association with peripheral neuropathy, cerebellar atrophy on imaging, an elevated alpha-fetoprotein (AFP) serum level, and occasional oculomotor apraxia. OBJECTIVE: To describe the clinical and molecular findings of 7 patients with a clinical presentation of AOA2 and their relatives. DESIGN: Case report. SETTING: Projet Hospitalier de Recherche Clinique. PATIENTS: Seven patients with AOA2 and their family members. INTERVENTION: Linkage analysis and direct sequencing of all exons of SETX were performed in all patients. Magnetic resonance imaging and electroneuromyography were performed and the patients' AFP serum levels were tested. RESULTS: We identified 7 patients with AOA2 from 4 unrelated families. Three novel SETX mutations were found. The clinical picture of the patients reported is fairly homogeneous and in accordance with the classic AOA2 presentation: onset from 13 to 18 years of progressive cerebellar ataxia and areflexia. Oculomotor apraxia was detected in 1 patient. Predominant axonal neuropathy and a diffuse cerebellar atrophy were found in the 4 patients tested. All patients had elevated AFP serum levels and 5 of 8 nonsymptomatic heterozygous relatives had moderately increased AFP serum levels as well. CONCLUSIONS: Ataxia with oculomotor apraxia type 2 is a homogeneous form of cerebellar ataxia with occasional oculomotor apraxia. Most nonsymptomatic heterozygous carriers present with increased AFP serum levels.