Cohen syndrome combined with psychiatric symptoms: a case report.

BACKGROUND: Cohen syndrome (CS) is a rare autosomal recessive inherited condition characterized by pathological changes affecting multiple systems. The extensive clinical variability associated with CS poses a significant diagnostic challenge. Additionally, there is limited documentation on the co-occurrence of CS with psychiatric symptoms. CASE REPORT: We report a case of a 30-year-old patient exhibiting characteristic physical features and psychiatric symptoms. Whole exome sequencing identified two heterozygous variants, a nonsense variation c.4336 C > T and a missense mutation c.4729G > A. Integrating clinical manifestations with genetic test results, we established the diagnosis of CS combined with psychiatric symptoms. CONCLUSIONS: This case introduces a novel missense variant as a candidate in the expanding array of VPS13B pathogenic variants. Its clinical significance remains unknown, and further investigation may broaden the spectrum of pathogenic variants associated with the VPS13B gene. Early diagnosis of CS is crucial for the prognosis of young children and holds significant importance for their families.

Cohen syndrome and early-onset epileptic encephalopathy in male triplets: two disease-causing mutations in VPS13B and NAPB.

Cohen syndrome (CS) is a rare multisystem autosomal recessive disorder associated with mutations in VPS13B (vacuolar protein sorting homolog 13B). The NAPB-related neurodevelopmental disorder is characterized mainly by early-onset epileptic encephalopathy (EOEE) and is associated with mutations in NAPB that encodes for SNAP-beta (soluble NSF attachment protein beta). Here we describe male triplets, clinically presenting with the phenotype of subtle but distinctive facial features, intellectual disability, increased body weight, neonatal EOEE, and prominently variable abnormal behaviors of autism and sexual arousal. The EEG showed multifocal epilepsy, while the brain MRI showed no abnormalities. Diagnostic exome sequencing (ES), the applied next-generation sequencing approach, revealed the interesting finding of two novel homozygous variants in two genes: VPS13B missense variant (c.8516G > A) and NAPB splice-site loss (c.354 + 2 T > G). Sanger sequencing verified the segregation of the two recessive gene variants with the phenotype in family members. The prediction algorithms support the pathogenicity of these variants. Homozygosity mapping of ES data of this consanguineous family revealed multiple chromosomal regions of homozygosity stretches with the residing of VPS13B (chr8: 100830758G > A) and NAPB (Chr20: 23,375,774 A > C) variants within the largest homozygous blocks further supporting the disease-genes causal role. Interestingly, the functions of the two proteins; VPS13B, a transmembrane protein involved in intracellular protein transport, and SNAP-beta involved in neurotransmitters release at the neuronal synaptic complexes, have been associated with Golgi-mediated vesicular trafficking. Our ES findings provide new insights into the pathologic mechanism underlying the expansion of the neurodevelopmental spectrum in CS and further highlight the importance of Golgi and Golgi-membrane-related proteins in the development of neurodevelopmental syndromes associated with early-onset non-channelopathy epilepsy. To our knowledge, this is the first report documenting multifocal EOEE in CS patients with the association of a pathogenic NAPB variant.

Characterization of Vps13b-mutant mice reveals neuroanatomical and behavioral phenotypes with females less affected.

The vacuolar protein sorting-associated protein 13B (VPS13B) is a large and highly conserved protein. Disruption of VPS13B causes the autosomal recessive Cohen syndrome, a rare disorder characterized by microcephaly and intellectual disability among other features, including developmental delay, hypotonia, and friendly-personality. However, the underlying mechanisms by which VPS13B disruption leads to brain dysfunction still remain unexplained. To gain insights into the neuropathogenesis of Cohen syndrome, we systematically characterized brain changes in Vps13b-mutant mice and compared murine findings to 235 previously published and 17 new patients diagnosed with VPS13B-related Cohen syndrome. We showed that Vps13b is differentially expressed across brain regions with the highest expression in the cerebellum, the hippocampus and the cortex with postnatal peak. Half of the Vps13b-/- mice die during the first week of life. The remaining mice have a normal lifespan and display the core phenotypes of the human disease, including microcephaly, growth delay, hypotonia, altered memory, and enhanced sociability. Systematic 2D and 3D brain histo-morphological analyses reveal specific structural changes in the brain starting after birth. The dentate gyrus is the brain region with the most prominent reduction in size, while the motor cortex is specifically thinner in layer VI. The fornix, the fasciculus retroflexus, and the cingulate cortex remain unaffected. Interestingly, these neuroanatomical changes implicate an increase of neuronal death during infantile stages with no progression in adulthood suggesting that VPS13B promotes neuronal survival early in life. Importantly, whilst both sexes were affected, some neuroanatomical and behavioral phenotypes were less pronounced or even absent in females. We evaluate sex differences in Cohen patients and conclude that females are less affected both in mice and patients. Our findings provide new insights about the neurobiology of VPS13B and highlight previously unreported brain phenotypes while defining Cohen syndrome as a likely new entity of non-progressive infantile neurodegeneration.

Early Diagnostic Signs and the Natural History of Typical Findings in Cohen Syndrome.

OBJECTIVE: To describe the clinical presentation and long-term clinical features of a molecularly confirmed cohort with Cohen syndrome. STUDY DESIGN: Twelve patients with Cohen syndrome aged 0.2-13.9 years from 8 families with a median follow-up of 7 years were enrolled to the study. Genetic analyses were made by VPS13B and whole-exome sequencing analyses. RESULTS: Biallelic VPS13B variants, including 3 nonsense, 1 frameshift, and 1 splice-site variant, and a multiexon deletion were detected. Prader-Willi syndrome-like features such as hypotonia, small hands, round face with full cheeks, almond-shaped eyes, and micrognathia were observed in all infantile patients. Beginning from age 4 years, it was noticed that the face gradually elongated and became oval. The typical facial features of Cohen syndrome such as a long face, beak-shaped nose, and open-mouth appearance with prominent upper central incisors became evident at age 9. Other Cohen syndrome features including retinopathy (11/11), neutropenia (11/12), truncal obesity (5/12), and myopia (5/11) were detected at the median ages of 7.8, 7, 7.5, and 5 years, respectively. Eleven patients aged older than 5 years at their last examination had severe speech delay. CONCLUSIONS: A differential diagnosis of Cohen syndrome in the infancy should be made with Prader-Willi syndrome, and that the typical facial features for Cohen syndrome is prominent at age 9 years, when retinopathy, neutropenia, and truncal obesity become evident. Moreover, adding the severe speech delay to the diagnostic criteria should be considered.

The Vps13 Family of Lipid Transporters and Its Role at Membrane Contact Sites.

The conserved VPS13 proteins constitute a new family of lipid transporters at membrane contact sites. These large proteins are suspected to bridge membranes and form a direct channel for lipid transport between organelles. Mutations in the 4 human homologs (VPS13A-D) are associated with a number of neurological disorders, but little is known about their precise functions or the relevant contact sites affected in disease. In contrast, yeast has a single Vps13 protein which is recruited to multiple organelles and contact sites. The yeast model system has proved useful for studying the function of Vps13 at different organelles and identifying the localization determinants responsible for its membrane targeting. In this review we describe recent advances in our understanding of VPS13 proteins with a focus on yeast research.

A novel VPS13B mutation in Cohen syndrome: a case report and review of literature.

BACKGROUND: Cohen syndrome, an autosomal recessive syndrome, is a rare syndrome with diverse clinical manifestations including failure to thrive, hypotonia, hypermobile joints, microcephaly, intellectual disabilities, craniofacial and limb anomalies, neutropenia and a friendly character. It is associated with mutations of the vacuolar protein sorting 13 homolog B (VPS13B) gene, which is involved in the development of the ocular, hematological and central nervous systems. This gene encodes a transmembrane protein playing a crucial role in preserving the integrity of the Golgi complex. To date, more than 150 mutations of VPS13B have been reported in over 200 Cohen syndrome patients. Missense or nonsense mutations are the most common mutations. CASE PRESENTATION: A 4-year-old girl, born to consanguineous parents, was referred to the pediatric clinical immunology outpatient clinic for investigation of recurrent neutropenia with a history of recurrent infections in the past year. On physical examination, she had the characteristic facial features of Cohen syndrome, developmental delay and speech disorder. She had a cheerful disposition, and her mother gave a history of feeding difficulties in her first months of life. She did not present any ophthalmologic or cardiac abnormalities. Her lab results revealed moderate neutropenia. Serum IgG, IgM, IgA and IgE levels were normal. She fulfilled the clinical diagnostic criteria for Cohen syndrome. WES revealed a novel homozygous frameshift variant in VPS13B (LRG_351t1: c.7095del; p.Ser2366AlafsTer49). Currently, she is not experiencing any severe problem, and she undergoes irregular medical treatment once her neutrophil count decreases under the normal limit. Her verbal and motor abilities have improved as a result of speech and occupational therapies. CONCLUSION: We reported a novel homozygous frameshift variant in VPS13B (LRG_351t1: c.7095del; p.Ser2366AlafsTer49) in a 4-year-old girl with Cohen syndrome. Cohen syndrome should be considered in differential diagnosis of any child with intellectual disability and neutropenia.

A novel homozygous nonsense mutation of VPS13B associated with previously unreported features of Cohen syndrome.

Cohen syndrome (CS) is a rare autosomal recessive disorder associated with mutations in the vacuolar protein sorting 13 homolog B (VPS13B; formerly COH1) gene. The core clinical phenotype comprises a characteristic facial gestalt, marked developmental delay, and myopia. Additional, nonobligatory features include obesity, microcephaly, short stature, muscular hypotonia, scoliosis, narrow hands and feet, progressive retinopathy, as well as neutropenia. Here we report a novel homozygous nonsense mutation in the VPS13B gene and previously undescribed clinical features in a 19-year-old woman with developmental delay, intellectual disability, and a particular facial appearance. The patient showed several features consistent with CS. In addition, the parents observed congenital alacrima and anhidrosis persisting until onset of puberty. The diagnosis was not established based on the clinical phenotype. We performed whole-genome sequencing and identified a novel homozygous nonsense mutation c.62T>G (NM_152564.4), p.(Leu21*) in the VPS13B gene. Our findings extended the previously reported phenotype of CS. We conclude that transient, prepubertal alacrima and anhidrosis are part of the phenotypic spectrum of CS associated with a novel homozygous nonsense mutation in the VPS13B gene.

Yeast and other lower eukaryotic organisms for studies of Vps13 proteins in health and disease.

Human Vps13 proteins are associated with several diseases, including the neurodegenerative disorder Chorea-acanthocytosis (ChAc), yet the biology of these proteins is still poorly understood. Studies in Saccharomyces cerevisiae, Dictyostelium discoideum, Tetrahymena thermophila and Drosophila melanogaster point to the involvement of Vps13 in cytoskeleton organization, vesicular trafficking, autophagy, phagocytosis, endocytosis, proteostasis, sporulation and mitochondrial functioning. Recent findings show that yeast Vps13 binds to phosphatidylinositol lipids via 4 different regions and functions at membrane contact sites, enlarging the list of Vps13 functions. This review describes the great potential of simple eukaryotes to decipher disease mechanisms in higher organisms and highlights novel insights into the pathological role of Vps13 towards ChAc.

Case report: two novel VPS13B mutations in a Chinese family with Cohen syndrome and hyperlinear palms.

BACKGROUND: Cohen syndrome (CS) is an uncommon developmental disease with evident clinical heterogeneity. VPS13B is the only gene responsible for CS. Only few sporadic cases of CS have been reported in China. CASE PRESENTATION: A Chinese family with two offspring-patients affected by developmental delay and intellectual disability was investigated in this study. Exome sequencing was performed, and compound heterozygous mutations in VPS13B were segregated for family members with autosomal recessive disorder. Splicing mutation c.3666 + 1G > T (exon 24) and nonsense mutation c. 9844 A > T:p.K3282X (exon 54) were novel. We revisited the family and learned that both patients are affected by microcephaly, developmental delay, neutropenia, and myopia and have a friendly disposition, all of which are consistent with CS phenotypes. We also found that both patients have hyperlinear palms, which their parents do not have. VPS13B mutations reported among the Chinese population were reviewed accordingly. CONCLUSIONS: This study presents two novel VPS13B mutations in CS. The identification of hyperlinear palms in a family affected by CS expands the phenotype spectrum of CS.

First case report of Cohen syndrome in the Tunisian population caused by VPS13B mutations.

BACKGROUND: Cohen syndrome is a rare autosomal recessive developmental disorder that comprises variable clinical features counting developmental delay, pigmentary retinopathy, myopia, acquired microcephaly, truncal obesity, joint hypermobility, friendly disposition and intermittent neutropenia. VPS13B (vacuolar protein sorting 13, yeast, homologue of B) gene is the only gene responsible for Cohen Syndrome, causative mutations include nonsense, missense, indel and splice-site variants. The integrity of the Golgi apparatus requires the presence of the peripheral membrane protein VPS13B that have an essential function in intracellular protein transport and vesicle-mediated sorting. CASE PRESENTATION: In this study, we performed whole exome sequencing (WES) in a Tunisian family with two young cases having developmental delay, hypotonia, autism spectrum disorder, ptosis and thick hair and eyebrows. The proposita presented also pigmentory retinopathy. Compound heterozygous mutation in VPS13B gene was detected by WES. This mutation inherited from healthy heterozygous parents, supports an unpredictable clinical diagnosis of Cohen Syndrome. The proband's phenotype is explained by the presence of compound heterozygous mutations in the VPS13B gene. This finding refined the understanding of genotype-phenotype correlation. CONCLUSIONS: This is the first report of a Tunisian family with Cohen syndrome mutated in the VPS13B gene.

The importance of phase analysis in multiexon copy number variation detected by aCGH in autosomal recessive disorder loci.

Cohen Syndrome (CS) is a rare autosomal recessive disorder caused by homozygous or compound heterozygous pathogenic variants in VPS13B, also known as COH1. Over 100 pathogenic variants in VSP13B, primarily truncations, and copy number variants, have been found in patients with CS. Here, we present an 11-month-old girl with CS caused by two multi-exonic small deletions in VSP13B in trans. Array comparative genomic hybridization has revolutionized the field of genome copy number analysis down to the exonic level, however it has its limitations. It cannot detect balanced structural variation nor determine the phase of copy number variants. Heterozygous multi-exonic copy number variation in autosomal recessive genes should be interpreted in the context of a clinical phenotype, and, if warranted, phase analysis should be performed before sequence analysis for that gene is pursued. This patient emphasizes the need of obtaining clinical information and determining the phase in multi-exonic copy number variants for accurate diagnosis and risk counseling.

Cohen syndrome-associated protein COH1 physically and functionally interacts with the small GTPase RAB6 at the Golgi complex and directs neurite outgrowth.

Postnatal microcephaly, intellectual disability, and progressive retinal dystrophy are major features of autosomal recessive Cohen syndrome, which is caused by mutations in the gene COH1 (VPS13B). We have recently identified COH1 as a Golgi-enriched scaffold protein that contributes to the structural maintenance and function of the Golgi complex. Here, we show that association of COH1 with the Golgi complex depends on the small GTPase RAB6. RNAi-mediated knockdown of RAB6A/A' prevents the localization of COH1 to the Golgi complex. Expression of the constitutively inactive RAB6_T27N mutant led to an increased solubilization of COH1 from lipid membrane preparations. Co-IP experiments confirmed the physical interaction of COH1 with RAB6 that preferentially occurred with the constitutively active RAB6_Q72L mutants. Depletion of COH1 in primary neurons negatively interfered with neurite outgrowth, indicating a causal link between the integrity of the Golgi complex and axonal outgrowth. We conclude that COH1 is a RAB6 effector protein and that reduced brain size in Cohen syndrome patients likely results from impaired COH1 function at the Golgi complex, causing decreased neuritogenesis.

Exome sequencing identifies pathogenic variants of VPS13B in a patient with familial 16p11.2 duplication.

BACKGROUND: The recurrent microduplication of 16p11.2 (dup16p11.2) is associated with a broad spectrum of neurodevelopmental disorders (NDD) confounded by incomplete penetrance and variable expressivity. This inter- and intra-familial clinical variability highlights the importance of personalized genetic counselling in individuals at-risk. CASE PRESENTATION: In this study, we performed whole exome sequencing (WES) to look for other genomic alterations that could explain the clinical variability in a family with a boy presenting with NDD who inherited the dup16p11.2 from his apparently healthy mother. We identified novel splicing variants of VPS13B (8q22.2) in the proband with compound heterozygous inheritance. Two VPS13B mutations abolished the canonical splice sites resulting in low RNA expression in transformed lymphoblasts of the proband. VPS13B mutation causes Cohen syndrome (CS) consistent with the proband's phenotype (intellectual disability (ID), microcephaly, facial gestalt, retinal dystrophy, joint hypermobility and neutropenia). The new diagnosis of CS has important health implication for the proband, provides the opportunity for more meaningful and accurate genetic counselling for the family; and underscores the importance of longitudinally following patients for evolving phenotypic features. CONCLUSIONS: This is the first report of a co-occurrence of pathogenic variants with familial dup16p11.2. Our finding suggests that the variable expressivity among carriers of rare putatively pathogenic CNVs such as dup16p11.2 warrants further study by WES and individualized genetic counselling of families with such CNVs.

Value of whole exome sequencing for syndromic retinal dystrophy diagnosis in young patients.

BACKGROUND: Several retinal dystrophies are associated with syndromic features including such conditions as Bardet-Biedl and Joubert syndromes. Cohen syndrome is an autosomal recessive disorder associated with multiple clinical manifestations including developmental delay, acquired microcephaly, myopia, pigmentary retinopathy, joint hypermobility, truncal obesity, friendly disposition and intermittent neutropenia. In young patients, diagnosis is difficult, because several of the characteristic features may not be present until school age or later years and the intermittent neutropenia is not always detectable. DESIGN: This was a prospective study using whole exome sequencing in syndromic retinal dystrophy. It was undertaken in a hospital and research institute setting. PARTICIPANTS: Participants in this study were members of a consanguineous Australian family of Lebanese ethnicity with two siblings with retinal dystrophy, microcephaly and developmental delay. METHODS: Detailed clinical evaluation was undertaken. Whole exome capture and sequencing of patient genomic DNA samples was followed by sequence alignment, variant detection, comparison and prioritization. MAIN OUTCOME MEASURES: Pathogenic variant identification in the disease-causing gene in affected individuals. RESULTS: We identified a novel homozygous deletion leading to a frameshift mutation in VPS13B, c.11327del, p.(Asn3776Thrfs*102), the disease gene associated with Cohen syndrome. CONCLUSIONS: This report emphasizes the value of a broad-based whole exome sequencing approach in disease gene identification in the syndromic retinal dystrophies, where all disease characteristics may not be present in young patients to allow a clinical diagnosis. This facilitates improved prognostic and genetic information for patients and families.

Congenital neutropenia with retinopathy, a new phenotype without intellectual deficiency or obesity secondary to VPS13B mutations.

Over one hundred VPS13B mutations are reported in Cohen syndrome (CS). Most cases exhibit a homogeneous phenotype that includes intellectual deficiency (ID), microcephaly, facial dysmorphism, slender extremities, truncal obesity, progressive chorioretinal dystrophy, and neutropenia. We report on a patient carrying two VPS13B splicing mutations with an atypical phenotype that included microcephaly, retinopathy, and congenital neutropenia, but neither obesity nor ID. RNA analysis of the IVS34+2T_+3AinsT mutation did not reveal any abnormal splice fragments but mRNA quantification showed a significant decrease in VPS13B expression. RNA sequencing analysis up- and downstream from the IVS57+2T>C mutation showed abnormal splice isoforms. In contrast to patients with typical CS, who express only abnormal VPS13B mRNA and truncated protein, a dose effect of residual normal VPS13B protein possibly explains the incomplete phenotype in the patient. This observation emphasizes that VPS13B analysis should be performed in cases of congenital neutropenia associated with retinopathy, even in the absence of ID, therefore extending the VPS13B phenotype spectrum.

Pseudohypoaldosteronism Type 1B and Cohen Syndrome: Novel Mutation, Unusual Combination, and Presentation.

Pseudohypoaldosteronism type 1 (PHA1) is a rare inherited disorder of resistance to aldosterone and presents with hyponatremia, hyperkalemia, and metabolic acidosis. Cohen syndrome (CS) is another rare inherited disease. Concurrent presentation with pseudohypoaldosteronism makes it so extraordinary and implies more challenges for clinicians. We report a case of a female with Cohen syndrome (novel mutation) and systemic pseudohypoaldosteronism, as well as the challenges we have encountered in the management of this patient.

Bilateral Subluxation of Microspherophakic Lens in a Child with Cohen Syndrome.

Cohen Syndrome is a rare autosomal recessive condition characterized by facial abnormalities with or without microcephaly, non-progressive intellectual delay, hypotonia, ophthalmic abnormalities, and neutropenia. Due to its low incidence and variable presentation, much about the disorder, including ophthalmic manifestations, is not fully understood. Here, we present the first documented case of a 5-year-old Amish child with Cohen Syndrome who presented with bilateral subluxation of microspherophakic lenses - rare findings themselves, let alone coexisting in a patient with a rare genetic syndrome. The child underwent bilateral lensectomy and is being managed with aphakic spectacles.

Deletion as novel variants in VPS13B gene in Cohen syndrome: Case series.

Background: Cohen syndrome (OMIM No. # 216550) is a rare autosomal recessive disorder caused by homozygous mutation in the vacuolar protein sorting 13 homolog B (VPS13B) gene on chromosome 8q22.2. Clinical manifestations include hypermobile joints, microcephaly, intellectual disabilities, craniofacial and limb anomalies, and neutropenia. To date, more than 200 mutations of VPS13B have been reported in over 1,000 Cohen syndrome patients. This article reviews the clinical data of two cases of Cohen syndrome diagnosed by whole exome sequencing. Results: Both children visited for psychomotor retardation. Gene detection showed a mutation in 8q22.2, NM_017890.4 Intron38 c.6940+1G > T and heterozygotic deletion of exon 3-19 of the VPS13B gene (Case 1), and a mutation in 8q22.2, NM_017890.4 Intron38 c.6940+1G > T and 8q22, NM_017890.4 Exon56 c10334_10335del in the VPS13B gene (Case 2). The variation was predicted to be pathogenic by related software, and they have not been reported. Conclusion: Cohen syndrome should be considered in the differential diagnosis of any child with developmental retardation and neutropenia. The present study increases the mutation spectrum of the VPS13B gene and could be helpful in genetic diagnosis and genetic counseling in Cohen syndrome patients.

Cohen Syndrome: Novel VPS13B Genetic Variants in a Male Portuguese Patient with Pigmentary Retinopathy.

The purpose of this clinical report was to describe a case of Cohen syndrome with its classical ophthalmological manifestations and novel VPS13B genetic variants. A 39-year-old Caucasian male patient with severe rod-cone retinal dystrophy and no history of parental consanguinity was referred to our ophthalmology department. Ophthalmologic history included high bilateral myopia and a 3-year prior bilateral cataract surgery. Systemic history included facial dysmorphism, intellectual disability, transient neutropenia, microcephaly, truncal obesity, and joint hyperextensibility. The patient presented classic fundoscopic features of pigmentary retinopathy in both eyes (OU). Optical coherence tomography (OCT) revealed bilateral central and diffuse retinal pigment epithelium (RPE) and outer retinal atrophy without concomitant macular edema, while fluorescein angiography (FA) demonstrated diffuse RPE atrophy with prominent choroidal vessels. The full-field ERG (ffERG) showed no dark-adapted or light-adapted responses and the P50 wave was not identified in the pattern ERG (pERG). The genetic study revealed two novel heterozygous variants in the VPS13B gene: (1) c.5138T>C p.(Leu1713Pro) and (2) c.10179del p.(Asn3393Lysfs*37), thus confirming the diagnosis of Cohen syndrome. This case report introduces these two novel genetic variants to the literature, in a patient with classic phenotypic characteristics of Cohen syndrome, a rare genetic disease which has been increasingly reported since its first description in 1973.

Ultrastructural Abnormalities in Induced Pluripotent Stem Cell-Derived Neural Stem Cells and Neurons of Two Cohen Syndrome Patients.

Cohen syndrome is an autosomal recessive disorder caused by VPS13B (COH1) gene mutations. This syndrome is significantly underdiagnosed and is characterized by intellectual disability, microcephaly, autistic symptoms, hypotension, myopia, retinal dystrophy, neutropenia, and obesity. VPS13B regulates intracellular membrane transport and supports the Golgi apparatus structure, which is critical for neuron formation. We generated induced pluripotent stem cells from two patients with pronounced manifestations of Cohen syndrome and differentiated them into neural stem cells and neurons. Using transmission electron microscopy, we documented multiple new ultrastructural changes associated with Cohen syndrome in the neuronal cells. We discovered considerable disturbances in the structure of some organelles: Golgi apparatus fragmentation and swelling, endoplasmic reticulum structural reorganization, mitochondrial defects, and the accumulation of large autophagosomes with undigested contents. These abnormalities underline the ultrastructural similarity of Cohen syndrome to many neurodegenerative diseases. The cell models that we developed based on patient-specific induced pluripotent stem cells can serve to uncover not only neurodegenerative processes, but the causes of intellectual disability in general.