Thin Corpus Callosum Research Articles

Novel RAB3GAP1 Mutation in the First Tunisian Family With Warburg Micro Syndrome.

Background and PurposeWarburg Micro syndrome (WARBM) is a rare autosomal recessive genetic disease characterized by ocular, neurologic, and endocrine anomalies. WARBM is a phenotypically and genetically heterogeneous syndrome caused by mutations in RAB3GAP1, RAB3GAP2, RAB18, and TBC1D20. Here we present the clinical and genetic characterization of a consanguineous Tunisian family with a WARBM phenotype presenting two pathogenic variations, one of which is on RAB3GAP1.MethodsWe applied whole-exome sequencing (WES) to two affected young males presenting a WARBM-compatible phenotype.ResultsWe reveal a new variation in RAB3GAP1 (NM_012233.3: c.297del, p.Gln99fs) and another variation in ABCD1 (NM_000033: c.896A>G, p.His299Arg). Each of these mutations, which in silico predictions concluded as being pathogenic variations, affects a critical protein region. Both affected males presented a WARBM-compatible phenotype, with severe intellectual disability, severe developmental delay, postnatal growth delay, postnatal microcephaly, congenital bilateral cataracts, general hypotonia, and a thin corpus callosum without a splenium. However, intrafamilial clinical heterogeneity was present, since only the oldest child had large ears, microphthalmia, foot deformities, and a genital anomaly, and only the youngest child had microcornea. Despite the mutation identified in ABCD1, our patients did not have any X-linked symptoms of adrenoleukodystrophy disorder that are usually caused by ABCD1 mutations, which prompted our interest in clinical monitoring.ConclusionsWES analysis of a consanguineous Tunisian family with WARBM revealed a novel variation in RAB3GAP1 (NM_012233.3: c.297del, p.Gln99fs) that is most likely pathogenic and allowed us to confirm the diagnosis of WARBM.

Possible EIF2AK2-Associated Stress-Related Neurological Decompensation with Combined Dystonia and Striatal Lesions.

Variants in EIF2AK2 have been recently associated with a spectrum of neurological disease encompassing isolated dystonia to fever-related neurological decompensation, movement disorders and leukodystrophy. A 32-year old patient presented with childhood-onset episodes of neurological decompensation after febrile illness, progressive anarthria, dystonia and spasticity. The T2/FLAIR MRI showed bilateral posterolateral putamen hyperintensities and white matter changes suggestive of leukodystrophy. Initial extensive metabolic workup and whole genome sequencing (WGS) was unremarkable. Re-analysis of the WGS data revealed a variant in exon 3 of the EIF2AK2 gene [(NM_001135651.3): c.92C > G (p.Pro31Arg)]. EIF2AK2-associated disorders should be incorporated into the differential diagnosis of the syndrome of fever-related neurological decompensation with movement disorders, especially in the presence of abnormal neuroimaging. Disease-causing variants in EIF2AK2 have been reported in 24 individuals from 16 families in the literature to date. Two broad phenotypes have been described, including: (1) childhood-onset generalized dystonia and a normal brain MRI; and (2) early childhood-onset developmental delay combined with movement disorders, spasticity, and seizures in some. Notably, 92% of these patients have neurological deterioration after febrile illness or other physiological stress. Hypomyelination or delayed myelination and thin corpus callosum are seen in most patients and lower medullary lessions are common. Basal ganglia lesions have been reported previously in one case. EIF2AK2-associated disorders should be incorporated into the differential diagnosis of the syndrome of fever-related neurological decompensation with movement disorders, especially in the presence of abnormal neuroimaging.

A homozygous ABHD16A variant causes a complex hereditary spastic paraplegia with developmental delay, absent speech, and characteristic face

Hereditary spastic paraplegia (HSP) is a genetically and clinically heterogeneous genetic disease characterized by progressive weakness and spasticity predominantly affecting the lower limbs. Complex HSP is a subset of HSP presenting with additional neuronal and/or non-neuronal phenotypes. Here, we identify a homozygous ABHD16A nonsense variant in two affected children in a Chilean family. Very recently, two groups reported patients with biallelic ABHD16A whose clinical presentation was similar to that of our patients. By reviewing the clinical features of these reports and our patients, ABHD16A-related HSP can be characterized by early childhood onset, developmental delay, intellectual disability, speech disturbance, extrapyramidal signs, psychiatric features, no sphincter control, skeletal involvement, thin corpus callosum, and high-intensity signals in white matter on T2-weighted brain MRI. In addition, our affected siblings showed a characteristic face, sleep disturbance, and nodular and hyperpigmented skin lesions, which have not previously been reported in this condition.

Pontocerebellar atrophy is the hallmark neuroradiological finding in late-onset Tay-Sachs disease.

Late-onset Tay-Sachs disease (LOTS) is a form of GM2 gangliosidosis, an autosomal recessive neurodegenerative disorder characterized by slowly progressive cerebellar ataxia, lower motor neuron disease, and psychiatric impairment due to mutations in the HEXA gene. The aim of our work was to identify the characteristic brain MRI findings in this presumably underdiagnosed disease. Clinical data and MRI findings from 16 patients (10F/6M) with LOTS from two centers were independently assessed by two readers and compared to 16 age- and sex-related controls. Lower motor neuron disease (94%), psychiatric symptoms-psychosis (31%), cognitive impairment (38%) and depression (25%)-and symptoms of cerebellar impairment including dysarthria (94%), ataxia (81%) and tremor (69%), were the most common clinical features. On MRI, pontocerebellar atrophy was a constant finding. Compared to controls, LOTS patients had smaller mean middle cerebellar peduncle diameter (p < 0.0001), mean superior cerebellar peduncle diameter (p = 0.0002), mesencephalon sagittal area (p = 0.0002), pons sagittal area (p < 0.0001), and larger 4th ventricle transversal diameter (p < 0.0001). Mild corpus callosum thinning (37.5%), mild cortical atrophy (18.8%), and white matter T2 hyperintensities (12.5%) were also present. Given the characteristic clinical course and MRI findings of the pontocerebellar atrophy, late-onset Tay-Sachs disease should be considered in the differential diagnosis of adult-onset cerebellar ataxias.

Bi-allelic variants in SPATA5L1 lead to intellectual disability, spastic-dystonic cerebral palsy, epilepsy, and hearing loss

Spermatogenesis-associated 5 like 1 (SPATA5L1) represents an orphan gene encoding a protein of unknown function. We report 28 bi-allelic variants in SPATA5L1 associated with sensorineural hearing loss in 47 individuals from 28 (26 unrelated) families. In addition, 25/47 affected individuals (53%) presented with microcephaly, developmental delay/intellectual disability, cerebral palsy, and/or epilepsy. Modeling indicated damaging effect of variants on the protein, largely via destabilizing effects on protein domains. Brain imaging revealed diminished cerebral volume, thin corpus callosum, and periventricular leukomalacia, and quantitative volumetry demonstrated significantly diminished white matter volumes in several individuals. Immunofluorescent imaging in rat hippocampal neurons revealed localization of Spata5l1 in neuronal and glial cell nuclei and more prominent expression in neurons. In the rodent inner ear, Spata5l1 is expressed in the neurosensory hair cells and inner ear supporting cells. Transcriptomic analysis performed with fibroblasts from affected individuals was able to distinguish affected from controls by principal components. Analysis of differentially expressed genes and networks suggested a role for SPATA5L1 in cell surface adhesion receptor function, intracellular focal adhesions, and DNA replication and mitosis. Collectively, our results indicate that bi-allelic SPATA5L1 variants lead to a human disease characterized by sensorineural hearing loss (SNHL) with or without a nonprogressive mixed neurodevelopmental phenotype.

Case report: Hereditary spastic paraplegia with thin corpus callosum

Hereditary spastic paraplegias (HSPs) are a group of inherited neurodegenerative disorders with clinical varieties depending on the genetic profile. Since 1981 it was established the clinical tableau into a pure and a complicated type which among other conditions encompasses mental retardation/cognitive impairments. The genetic profile is as heterogeneous as the clinical one including autosomal dominant, x-linked, and autosomal recessive mode of inheritance. HSP with thin corpus callosum(TCC) is an autosomal recessive form of the disease with a few reported cases in Japan and a limited number of Caucasian patients.

TH16. A PIPELINE TO PROCESS AND ANALYSE EXOME SEQUENCING DATA FROM 200,000 INDIVIDUALS IN THE UK BIOBANK

Molecular diagnosis of hereditary spastic paraplegias (HSP) is a difficult task due to great clinical and genetic heterogeneity. We aimed to characterize clinical and molecular findings of HSP families from Rio Grande do Sul, Brazil; and to evaluate the diagnostic yield of a next-generation sequencing (NGS) panel with twelve HSP-related genes.A consecutive series of HSP index cases with familial recurrence of spasticity, consanguinity or thin corpus callosum (TCC) were included in this cross-sectional study.Among the 29 index cases, 51.7% (15/29) received at least a likely molecular diagnosis, and 48.3% (14/29) a defined diagnosis. NGS panel diagnostic yield was 60% for autosomal dominant HSP (6/10, all SPG4), 47.4% for autosomal recessive HSP (9/19: 5 SPG11, 2 SPG7, 1 SPG5 and 1 cerebrotendinous xanthomatosis), and 50% for patients with TCC (3/6, all SPG11). Remarkably, 2/6 SPG11 patients presented keratoconus, and tendon xanthomas were absent in the patient with cerebrotendinous xanthomatosis.A likely molecular diagnosis was obtained for more than half of families with the NGS panel, indicating that this approach could be employed as a first-line investigation for HSP. SPG4 is the most frequent form of autosomal dominant and SPG11 of autosomal recessive HSP in Southern Brazil.

Systematic Analysis of Brain MRI Findings in Adaptor Protein Complex 4-Associated Hereditary Spastic Paraplegia.

AP-4-associated hereditary spastic paraplegia (AP-4-HSP: SPG47, SPG50, SPG51, SPG52) is an emerging cause of childhood-onset hereditary spastic paraplegia and mimic of cerebral palsy. This study aims to define the spectrum of brain MRI findings in AP-4-HSP and to investigate radioclinical correlations. We performed a systematic qualitative and quantitative analysis of 107 brain MRI studies from 76 individuals with genetically confirmed AP-4-HSP and correlation with clinical findings including surrogates of disease severity. We define AP-4-HSP as a disorder of gray and white matter and demonstrate that abnormal myelination is common and that metrics of reduced white matter volume correlate with severity of motor symptoms. We identify a common diagnostic imaging signature consisting of (1) a thin splenium of the corpus callosum, (2) an absent or thin anterior commissure, (3) characteristic signal abnormalities of the forceps minor ("ears of the grizzly sign"), and (4) periventricular white matter abnormalities. The presence of 2 or more of these findings has a sensitivity of ∼99% for detecting AP-4-HSP; the combination of all 4 is found in ∼45% of cases. Compared to other HSPs with a thin corpus callosum, the absent anterior commissure appears to be specific to AP-4-HSP. Our analysis identified a subset of patients with polymicrogyria, underscoring the role of AP-4 in early brain development. These patients displayed a higher prevalence of seizures and status epilepticus, many at a young age. Our findings define the MRI spectrum of AP-4-HSP, providing opportunities for early diagnosis, identification of individuals at risk for complications, and a window into the role of the AP-4 complex in brain development and neurodegeneration.

Novel CLCN4 variant associated with syndromic X-linked intellectual disability in a Chinese girl: a case report

BackgroundThe Raynaud-Claes type of X-linked syndromic mental retardation (MRXSRC) is a very rare condition, by intellectual disability ranged from borderline to profound, impaired language development, brain abnormalities, facial dysmorphisms and seizures. MRXSRC is caused by variants in CLCN4 which encodes the 2Cl−/H+ exchanger ClC-4 prominently expressed in brain.Case presentationWe present a 3-year-old Chinese girl with intellectual disability, dysmorphic features, brain abnormalities, significant language impairment and autistic features. Brain magnetic resonance imaging (MRI) showed a thin corpus callosum, a mega cisterna magna and ventriculomegaly. Whole exome sequencing (WES) was performed to detect the molecular basis of the disease. It was confirmed that this girl carried a novel heterozygous missense variant (c.1343C > T, p.Ala448Val) of CLCN4 gene, inherited from her mother. This variant has not been registered in public databases and was predicted to be pathogenic by multiple in silico prediction tools.ConclusionOur investigation expands the phenotype spectrum for CLCN4 variants with syndromic X-linked intellectual disability, which help to improve the understanding of CLCN4-related intellectual disability and will help in genetic counselling for this family.

Phenotype associated with TAF2 biallelic mutations: A clinical description of four individuals and review of the literature

Transcription factor IID is a multimeric protein complex that is essential for the initiation of transcription by RNA polymerase II. One of its critical components, the TATA-binding protein-associated factor 2, is encoded by the gene TAF2. Pathogenic variants of this gene have been shown to be responsible for the Mental retardation, autosomal recessive 40 syndrome. This syndrome is characterized by severe intellectual disability, postnatal microcephaly, pyramidal signs and thin corpus callosum. Until now, only three families have been reported separately. Here we report four individuals, from two unrelated families, who present with severe intellectual disability and global developmental delay, postnatal microcephaly, feet deformities and thin corpus callosum and who carry homozygous TAF2 missense variants detected by Exome Sequencing. Taken together, our findings and those of previously reported subjects allow us to further delineate the clinical phenotype associated with TAF2 biallelic mutations.

Genetic, clinical and neuroimaging profiles of sporadic and autosomal recessive hereditary spastic paraplegia cases in Chinese

Spastic paraplegias (SPGs) are a group of clinically and genetically heterogeneous neurodegenerative diseases. Mutations in 78 genes have been identified in autosomal dominant hereditary SPG (AD-HSP) and autosomal recessive hereditary SPG (AR-HSP). Compared to familial HSP, much less is known about the genetic and clinical profiles of sporadic SPGs. In this study, we have screened mutations for 18 sporadic SPGs or AR-HSP patients (mainly Northern Chinese) by whole-exome sequencing. We identified 12 mutations in five genes in 9 (50%) patients, including 9 novel ones: SPG5A/CYP7B1 (c.851C > A; c.122 + 2 T > G), SPG11/KIAA1840 (c.1735 + 3_ 1735 + 6del AAGT); SPG7/SPG7 (c.1454G > A; c.1892_ 1906dup GAGGACGGGCCTCGG); SPG39/PNPLA6 (c.1591G > A; c. 2990C > T); SPG15/ ZFYVE26 (c. 4804C > T; c. 4278 G > A). Among all the mutations, 7 were detected in the SPG5A and SPG11. Age at onset was significantly younger in cases with mutations (15.45 ± 6.78 years) than those without mutations (25.56 ± 10.90 years) (P = 0.03). Except for two cases with the SPG5A mutations, all cases presented with complicated SPGs. Three cases carrying mutations in SPG7, SPG15, SPG39 showed symptoms and signs of ataxia. One case carrying the homozygous c.259 + 2 T > C mutation in CYP7B1 showed serum parameters indicating liver impairment. Magnetic resonance imaging showed significantly thinned corpus callosum in cases with SPG11 and SPG15, but not in those with SPG5A, SPG7 or SPG39. In contrast, cerebellar atrophy was prominent in the SPG7 and SPG39 cases. These findings expand the spectrum of genetic, clinical and imaging features of sporadic SPG and AR-HSP, and have important implications in genetic counselling, molecular mechanisms and precise diagnosis of the disease.

Global developmental delay, systemic dysmorphism and epilepsy in a patient with a de novo U2AF2 variant.

U2 small nuclear RNA auxiliary factor 2 (U2AF2) is an essential pre-mRNA splicing factor in an early step of splicing. Alternative splicing plays an important role in neuronal development, and disorders of RNA processing steps are implicated in neurological disorders. Recently, the large trio whole-exome sequencing study reported U2AF2 as a novel gene significantly associated with developmental disorders: however, the clinical details of patients with U2AF2 variants were not available. Here, we report an individual with a de novo U2AF2 variant (c.445C>T, p.(Arg149Trp)) using trio-based whole-exome sequencing. This residue was positioned in the RNA recognition motif 1 which recognizes a polypyrimidine-tract splice site signal. The patient showed global developmental delay, intellectual disability, epilepsy, short stature, microcephaly, facial dysmorphism, intermittent exotropia, bilateral ptosis, muscle hypotonia and thin corpus callosum, indicating that U2AF2-related disorder could include systemic dysmorphisms, epilepsy and brain malformation along with global developmental delay.

Mutations in HID1 Cause Syndromic Infantile Encephalopathy and Hypopituitarism.

Objective:Precursors of peptide hormones undergo posttranslational modifications within the trans-Golgi network (TGN). Dysfunction of proteins involved at different steps of this process cause several complex syndromes affecting the central nervous system (CNS). We aimed to clarify the genetic cause in a group of patients characterized by hypopituitarism in combination with brain atrophy, thin corpus callosum, severe developmental delay, visual impairment, and epilepsy.Methods:Whole exome sequencing was performed in seven individuals of six unrelated families with these features. Postmortem histopathological and HID1 expression analysis of brain tissue and pituitary gland were conducted in one patient. Functional consequences of the homozygous HID1 variant p.R433W were investigated by Seahorse XF Assay in fibroblasts of two patients.Results:Bi-allelic variants in the gene HID1 domain-containing protein 1 (HID1) were identified in all patients. Postmortem examination confirmed cerebral atrophy with enlarged lateral ventricles. Markedly reduced expression of pituitary hormones was found in pituitary gland tissue. Colocalization of HID1 protein with the TGN was not altered in fibroblasts of patients compared to controls, while the extracellular acidification rate upon stimulation with potassium chloride was significantly reduced in patient fibroblasts compared to controls.Interpretation:Our findings indicate that mutations in HID1 cause an early infantile encephalopathy with hypopituitarism as the leading presentation, and expand the list of syndromic CNS diseases caused by interference of TGN function.

HIV-induced neuroinflammation inhibits oligodendrocyte maturation via glutamate-dependent activation of the PERK arm of the integrated stress response.

Despite combined antiretroviral therapy (cART), HIV-associated neurocognitive disorder (HAND) affects 30-50% of HIV-positive patients. Importantly, persistent white matter pathologies, specifically corpus callosum thinning and disruption of white matter microstructures observed in patients with HAND despite viral control through cART, raise the possibility that HIV infection in the setting of suboptimal cART may perturb oligodendrocyte (OL) maturation, function and/or survival, influencing HAND persistence in the cART era. To examine the effect of HIV infection on OL maturation, we used supernatants of primary human monocyte-derived macrophages infected with HIV (HIV/MDMs) to treat primary cultures of rat oligodendrocyte precursor cells (OPCs) during their differentiation to mature OLs. Using immunostaining for lineage-specific markers, we found that HIV/MDMs significantly inhibited OPC maturation. Based on our previous studies, we examined the potential role of several signaling pathways, including ionotropic glutamate receptors and the integrated stress response (ISR), and found that AMPA receptors (AMPAR)/kainic acid (KA) receptors (KARs) mediated the HIV/MDMs-induced defect in OL maturation. We also found that the treatment of OPC cultures with glutamate or AMPAR/KAR agonists phenocopied this effect. Blocking ISR activation, specifically the PERK arm of the ISR, protected OPCs from HIV/MDMs-mediated inhibition of OL maturation. Further, while glutamate, AMPA, and KA activated the ISR, inhibition of AMPAR/KAR activation prevented ISR induction in OPCs and rescued OL maturation. Collectively, these data identify glutamate signaling via ISR activation as a potential therapeutic pathway to ameliorate white matter pathologies in HAND and highlight the need for further investigation of their contribution to cognitive impairment.

Further Delineation of the Clinical and Pathologic Features of HIKESHI-Related Hypomyelinating Leukodystrophy

BackgroundA recurrent homozygous missense variant, c.160G>C;p.(Val54Leu) in HIKESHI, was found to cause a hypomyelinating leukodystrophy with high frequency in the Ashkenazi Jewish population. We provide extended phenotypic classification of this disorder based on clinical history of a further seven affected individuals, assess carrier frequency in the Ashkenazi Jewish population, and provide a neuropathological study. MethodsClinical information, neuroimaging, and biosamples were collected. Brain autopsy was performed for one case. ResultsIndividuals with HIKESHI-related disease share common clinical features: early axial hypotonia evolving to dystonia or with progressive spasticity, hyperreflexia and clonus, feeding difficulties with poor growth, and nystagmus. Severe morbidity or death during febrile illness occurred in five of the nine affected individuals. Magnetic resonance images of seven patients were analyzed and demonstrated diffuse hypomyelination and thin corpus callosum. Genotyping data of more than 125,000 Ashkenazi Jewish individuals revealed a carrier frequency of 1 in 216. Gross pathology examination in one case revealed abnormal white matter. Microscopically, there was a near-total absence of myelin with a relative preservation of axons. The cerebral white matter showed several reactive astrocytes and microglia. ConclusionsWe provide pathologic evidence for a primary disorder of the myelin in HIKESHI-related leukodystrophy. These findings are consistent with the hypomyelination seen in brain magnetic resonance imaging and with the clinical features of early-onset spastic/dystonic quadriplegia and nystagmus. The high carrier rate of the recurrent variant seen in the Ashkenazi Jewish population requires increased attention to screening and diagnosis of this condition, particularly in this population.

Clinical, neuroimaging, and molecular spectrum of TECPR2-associated hereditary sensory and autonomic neuropathy with intellectual disability.

Bi-allelic TECPR2 variants have been associated with a complex syndrome with features of both a neurodevelopmental and neurodegenerative disorder. Here, we provide a comprehensive clinical description and variant interpretation framework for this genetic locus. Through international collaboration, we identified 17 individuals from 15 families with bi-allelic TECPR2-variants. We systemically reviewed clinical and molecular data from this cohort and 11 cases previously reported. Phenotypes were standardized using Human Phenotype Ontology terms. A cross-sectional analysis revealed global developmental delay/intellectual disability, muscular hypotonia, ataxia, hyporeflexia, respiratory infections, and central/nocturnal hypopnea as core manifestations. A review of brain magnetic resonance imaging scans demonstrated a thin corpus callosum in 52%. We evaluated 17 distinct variants. Missense variants in TECPR2 are predominantly located in the N- and C-terminal regions containing β-propeller repeats. Despite constituting nearly half of disease-associated TECPR2 variants, classifying missense variants as (likely) pathogenic according to ACMG criteria remains challenging. We estimate a pathogenic variant carrier frequency of 1/1221 in the general and 1/155 in the Jewish Ashkenazi populations. Based on clinical, neuroimaging, and genetic data, we provide recommendations for variant reporting, clinical assessment, and surveillance/treatment of individuals with TECPR2-associated disorder. This sets the stage for future prospective natural history studies.

White matter abnormalities and iron deposition in prenatal mucolipidosis IV- fetal imaging and pathology.

Mucolipidosis type IV (MLIV; OMIM 252,650) is an autosomal recessive lysosomal disorder caused by mutations in MCOLN1. MLIV causes psychomotor impairment and progressive vision loss. The major hallmarks of postnatal brain MRI are hypomyelination and thin corpus callosum. Human brain pathology data is scarce and demonstrates storage of various inclusion bodies in all neuronal cell types. The current study describes novel fetal brain MRI and neuropathology findings in a fetus with MLIV.Fetal MRI was performed at 32 and 35weeks of gestation due to an older sibling with spastic quadriparesis, visual impairment and hypomyelination. Following abnormal fetal MRI results, the parents requested termination of pregnancy according to Israeli regulations. Fetal autopsy was performed after approval of the high committee for pregnancy termination. A genetic diagnosis of MLIV was established in the fetus and sibling. Sequential fetal brain MRI showed progressive curvilinear hypointensities on T2-weighted images in the frontal deep white matter and a thin corpus callosum. Fetal brain pathology exhibited a thin corpus callosum and hypercellular white matter composed of reactive astrocytes and microglia, multifocal white matter abnormalities with mineralized deposits, and numerous aggregates of microglia with focal intracellular iron accumulation most prominent in the frontal lobes. This is the first description in the literature of brain MRI and neuropathology in a fetus with MLIV. The findings demonstrate prenatal white matter involvement with significant activation of microglia and astrocytes and impaired iron metabolism.

OTUD5 Variants Associated With X-Linked Intellectual Disability and Congenital Malformation.

BackgroundX-linked intellectual disability (XLID), which occurs predominantly in males, is a relatively common and genetically heterogeneous disorder in which over 100 mutated genes have been reported. The OTUD5 gene at Xp11.23 encodes ovarian tumor deubiquitinase 5 protein, which is a deubiquitinating enzyme member of the ovarian tumor family. LINKage-specific-deubiquitylation-deficiency-induced embryonic defects (LINKED) syndrome, arising from pathogenic OTUD5 variants, was recently reported as a new XLID with additional congenital anomalies.MethodsWe investigated three affected males (49- and 47-year-old brothers [Individuals 1 and 2] and a 2-year-old boy [Individual 3]) from two families who showed developmental delay. Their common clinical features included developmental delay, hypotonia, short stature, and distinctive facial features, such as telecanthus and a depressed nasal bridge. Individuals 1 and 2 showed epilepsy and brain magnetic resonance imaging showed a thin corpus callosum and mild ventriculomegaly. Individual 3 showed congenital malformations, including tetralogy of Fallot, hypospadias, and bilateral cryptorchidism. To identify the genetic cause of these features, we performed whole-exome sequencing.ResultsA hemizygous OTUD5 missense variant, c.878A>T, p.Asn293Ile [NM_017602.4], was identified in one family with Individuals 1 and 2, and another missense variant, c.1210 C>T, p.Arg404Trp, in the other family with Individual 3, respectively. The former variant has not been registered in public databases and was predicted to be pathogenic by multiple in silico prediction tools. The latter variant p.Arg404Trp was previously reported as a pathogenic OTUD5 variant, and Individual 3 showed a typical LINKED syndrome phenotype. However, Individuals 1 and 2, with the novel variant (p.Asn293Ile), showed no cardiac or genitourinary malformations.ConclusionsUnlike previous reports of LINKED syndrome, which described early lethality with congenital cardiac anomalies, our three cases are still alive. Notably, the adult brothers with the novel missense OTUD5 variant have lived into their forties. This may be indicative of a milder phenotype as a possible genotype-phenotype correlation. These findings imply a possible long-term prognosis for individuals with this new XLID syndrome, and a wider phenotypic variation than initially thought.

Investigating ZFYVE26 mutations in a Taiwanese cohort with hereditary spastic paraplegia

Hereditary spastic paraplegia (HSP) is a heterogeneous group of inherited neurodegenerative disorders characterized by slowly progressive lower limbs spasticity and weakness. HSP type 15 (SPG15) is an autosomal recessive subtype caused by ZFYVE26 mutations. The aim of this study was to investigate the frequency and clinical and genetic features of ZFYVE26 mutations in a Taiwanese HSP cohort. Mutational analysis of the coding regions of ZFYVE26 was performed by targeted resequencing in the 195 unrelated Taiwanese patients with HSP. All of the patients were of Han Chinese ethnicity. Clinical, neuropsychological, electrophysiological evaluations and imaging studies were collected. Among the 195 patients, only one SPG15 patient was identified. The patient had a novel recessive ZFYVE26 frameshift truncating mutation, p.R1806Gfs∗36 (c.5415delC), and presented with insidious onset spastic weakness of lower-extremities and cognitive impairment. Neuropsychological assessment revealed deficits in executive function, visual naming, category verbal fluency, and manual dexterity. Brain MRI showed thin corpus callosum and the "ears of lynx" sign. SPG15 accounts for approximately 0.5% (1/195) of the Taiwanese HSP cohort. This study identified the first Taiwanese SPG15 case and delineated the clinical, genetic, neuropsychological, and neuroimaging features. These findings expand the mutational spectrum of ZFYVE26 and also broaden the knowledge of clinical and neuropsychological characteristics of SPG15.

Pathologic basis of the preferential thinning of thecorpus callosum in adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP).

BackgroundAdult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is an early onset dementia characterized by axonal loss in the cerebral white matter with swollen axons (spheroids). It had been reported that the preferential thinning and “focal lesions” of the corpus callosum were observed on T2-weighted MRI in ALSP patients. The present study aimed to reveal the pathologic basis of them in relation to brain lesion staging (I ~ IV: Oyanagi et al. 2017).MethodsSeven autopsied brains of ALSP and five controls were neuropathologically examined.ResultsEven at Stage I, corpus callosum body showed evident atrophy, and the atrophy advanced with stage progression. Spheroid size and density were maximal at Stage II in both centrum semiovale and corpus callosum body, but spheroids were larger in corpus callosum body than in centrum semiovale. Microglia in the body at Stage II had a larger cytoplasm than those in centrum semiovale. But spheroids and microglia in the “focal lesions” were identical with those of centrum semiovale.ConclusionPreferential thinning of corpus callosum was considered to be formed in relation to peculiar morphological alteration of microglia there in ALSP. Instead, “focal lesions” were formed in connection with the lesions in centrum semiovale.