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Dobloug S, Kjellström U, Anderson G, Gardner E, Mole SE, Sheth J, Puschmann A. Maculopathy and adult-onset ataxia in patients with biallelic MFSD8 variants. Mol Genet Genomic Med 2024; 12:e2505. [PMID: 39108195 PMCID: PMC11303817 DOI: 10.1002/mgg3.2505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2024] [Revised: 07/17/2024] [Accepted: 07/24/2024] [Indexed: 08/10/2024] Open
Abstract
BACKGROUND Biallelic variants in the major facilitator superfamily domain containing 8 gene (MFSD8) are associated with distinct clinical presentations that range from typical late-infantile neuronal ceroid lipofuscinosis type 7 (CLN7 disease) to isolated adult-onset retinal dystrophy. Classic late-infantile CLN7 disease is a severe, rare neurological disorder with an age of onset typically between 2 and 6 years, presenting with seizures and/or cognitive regression. Its clinical course is progressive, leading to premature death, and often includes visual loss due to severe retinal dystrophy. In rare cases, pathogenic variants in MFSD8 can be associated with isolated non-syndromic macular dystrophy with variable age at onset, in which the disease process predominantly or exclusively affects the cones of the macula and where there are no neurological or neuropsychiatric manifestations. METHODS Here we present longitudinal studies on four adult-onset patients who were biallelic for four MFSD8 variants. RESULTS Two unrelated patients who presented with adult-onset ataxia and had macular dystrophy on examination were homozygous for a novel variant in MFSD8 NM_152778.4: c.935T>C p.(Ile312Thr). Two other patients presented in adulthood with visual symptoms, and one of these developed mild to moderate cerebellar ataxia years after the onset of visual symptoms. CONCLUSIONS Our observations expand the knowledge on biallelic pathogenic MFSD8 variants and confirm that these are associated with a spectrum of more heterogeneous clinical phenotypes. In MFSD8-related disease, adult-onset recessive ataxia can be the presenting manifestation or may occur in combination with retinal dystrophy.
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Affiliation(s)
- Sigurd Dobloug
- Department of NeurologyHelsingborg General HospitalHelsingborgSweden
- Department for Clinical Sciences, Lund, NeurologyLund UniversityLundSweden
| | | | - Glenn Anderson
- Department of HistopathologyGreat Ormond Street HospitalLondonUK
| | - Emily Gardner
- Great Ormond Street Institute of Child HealthUniversity College LondonLondonUK
| | - Sara E. Mole
- Great Ormond Street Institute of Child HealthUniversity College LondonLondonUK
| | - Jayesh Sheth
- Foundation for Research in Genetics and EndocrinologyInstitute of Human GeneticsAhmedabadIndia
| | - Andreas Puschmann
- Lund University, Skåne University Hospital, NeurologyLundSweden
- SciLifeLabLund UniversityLundSweden
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Kayani S, Edgar VB, Lowden A, Nettesheim ER, Dahshi H, Messahel S, Minassian BA, Greenberg BM. Neuronal Ceroid Lipofuscinoses Type 7 (CLN7)- A Case Series Reporting Cross Sectional and Retrospective Clinical Data to Evaluate Validity of Standardized Tools to Assess Disease Progression, Quality of Life, and Adaptive Skills. RESEARCH SQUARE 2024:rs.3.rs-3983366. [PMID: 38978590 PMCID: PMC11230482 DOI: 10.21203/rs.3.rs-3983366/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Background This study evaluated the clinical characteristics of neuronal ceroid lipofuscinosis type 7 or CLN7 disease spectrum to characterize the clinical, electrophysiologic and neuroimaging phenotypes. Methods We performed a single-center cross sectional data collection along with retrospective medical chart review in patients with a genetic diagnosis of CLN7. This study received ethical approval by the University of Texas Southwestern Medical Center Institutional Review Board. A total of 8 patients were included between the ages of 4 to 6 years. All patients had a genetic diagnosis of CLN7 with homozygous or compound heterozygous mutations in the MFSD8 gene. The information collected includes patient demographics, developmental history, neurological events including seizures and neurodevelopmental regression along with further evaluation of brain magnetic resonance imaging and electrophysiological findings. The clinical phenotype is described through cross sectional and retrospective data collection and standardized tools assessing quality of life and functional skills. Conclusions Our findings in this cohort of CLN7 patients indicated that development is initially normal with onset of clinical symptoms as early as two years of age. Language problems were noted prior to or at the onset of seizures in all cases. Gait problems were noted prior to seizure onset in 3 of 8 patients, and at or within 6 months after the onset of seizures in 5 of 8 patients. All patients followed a progressive course of language, motor, and neurocognitive deterioration. Congruent with the medical history, our patients had significantly low scores on adaptive abilities. Natural history data such as this can be used to support future clinical trial designs.
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Affiliation(s)
- Saima Kayani
- UT Southwestern: The University of Texas Southwestern Medical Center
| | | | - Andrea Lowden
- UT Southwestern: The University of Texas Southwestern Medical Center
| | | | - Hamza Dahshi
- UT Southwestern: The University of Texas Southwestern Medical Center
| | - Souad Messahel
- UT Southwestern: The University of Texas Southwestern Medical Center
| | - Berge A Minassian
- UT Southwestern: The University of Texas Southwestern Medical Center
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Linear Diagnostic Procedure Elicited by Clinical Genetics and Validated by mRNA Analysis in Neuronal Ceroid Lipofuscinosis 7 Associated with a Novel Non-Canonical Splice Site Variant in MFSD8. Genes (Basel) 2023; 14:genes14020245. [PMID: 36833170 PMCID: PMC9956376 DOI: 10.3390/genes14020245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/08/2023] [Accepted: 01/16/2023] [Indexed: 01/19/2023] Open
Abstract
Neuronal ceroid lipofuscinoses (CNL) are lysosomal storage diseases that represent the most common cause of dementia in children. To date, 13 autosomal recessive (AR) and 1 autosomal dominant (AD) gene have been characterized. Biallelic variants in MFSD8 cause CLN7 type, with nearly 50 pathogenic variants, mainly truncating and missense, reported so far. Splice site variants require functional validation. We detected a novel homozygous non-canonical splice-site variant in MFSD8 in a 5-year-old girl who presented with progressive neurocognitive impairment and microcephaly. The diagnostic procedure was elicited by clinical genetics first, and then confirmed by cDNA sequencing and brain imaging. Inferred by the common geographic origin of the parents, an autosomal recessive inheritance was hypothesized, and SNP-array was performed as the first-line genetic test. Only three AR genes lying within the observed 24 Mb regions of homozygosity were consistent with the clinical phenotype, including EXOSC9, SPATA5 and MFSD8. The cerebral and cerebellar atrophy detected in the meantime by MRI, along with the suspicion of accumulation of ceroid lipopigment in neurons, prompted us to perform targeted MFSD8 sequencing. Following the detection of a splice site variant of uncertain significance, skipping of exon 8 was demonstrated by cDNA sequencing, and the variant was redefined as pathogenic.
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A Novel, Apparently Silent Variant in MFSD8 Causes Neuronal Ceroid Lipofuscinosis with Marked Intrafamilial Variability. Int J Mol Sci 2022; 23:ijms23042271. [PMID: 35216386 PMCID: PMC8877174 DOI: 10.3390/ijms23042271] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/09/2022] [Accepted: 02/16/2022] [Indexed: 02/06/2023] Open
Abstract
Variants in MFSD8 can cause neuronal ceroid lipofuscinoses (NCLs) as well as nonsyndromic retinopathy. The mutation spectrum includes mainly missense and stop variants, but splice sites and frameshift variants have also been reported. To date, apparently synonymous substitutions have not been shown to cause MFSD8-associated diseases. We report two closely related subjects from a consanguineous Turkish family who presented classical features of NCLs but demonstrated marked intrafamilial variability in age at the onset and severity of symptoms. In fact, the difference in the onset of first neurologic symptoms was 15 years and that of ophthalmologic symptoms was 12 years. One subject presented an intellectual disability and a considerable cerebellar ataxia syndrome, while the other subject showed no intellectual disability and only a mild atactic syndrome. The diagnostic genetic testing of both subjects based on genome sequencing prioritized a novel, apparently synonymous variant in MFSD8, which was found in homozygosity in both subjects. The variant was not located within an integral part of the splice site consensus sequences. However, the bioinformatic analyses suggested that the mutant allele is more likely to cause exon skipping due to an altered ratio of exonic splice enhancer and silencer motifs. Exon skipping was confirmed in vitro by minigene assays and in vivo by RNA analysis from patient lymphocytes. The mutant transcript is predicted to result in a frameshift and, if translated, in a truncated protein. Synonymous variants are often given a low priority in genetic diagnostics because of their expected lack of functional impact. This study highlights the importance of investigating the impact of synonymous variants on splicing.
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Novel MFSD8 Variants in a Chinese Family with Nonsyndromic Macular Dystrophy. J Ophthalmol 2021; 2021:6684045. [PMID: 34457359 PMCID: PMC8387190 DOI: 10.1155/2021/6684045] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 07/04/2021] [Accepted: 07/05/2021] [Indexed: 11/25/2022] Open
Abstract
Purpose To identify the molecular etiology of a Chinese family with nonsyndromic macular dystrophy. Methods Ophthalmic examinations were performed, and genomic DNA was extracted from available family members. Whole exome sequencing of two members (the proband and her unaffected mother) and Sanger sequencing in available family members were performed to screen potential pathogenic variants. Results Novel compound heterozygous variants, c.1066C>T (p.Pro356Ser) and c.1102+2T>C, in the major facilitator superfamily domain containing 8 gene (MFSD8) were suspected to be involved in this family's macular dystrophy phenotype. The novel c.1066C>T variant in the MFSD8 gene probably resulted in substitution of serine for proline at the 356th residue and was predicted to be “uncertain significance” through in silico analyses. The novel c.1102+2T>C variant in the MFSD8 gene was likely to affect the splicing form and predicted to be “pathogenic.” Conclusion The novel compound heterozygous variants, c.1066C>T (p.Pro356Ser) and c.1102+2T>C, in the MFSD8 gene are likely responsible for the isolated macular dystrophy phenotype in this family. This study enlarged the MFSD8 gene mutant spectrum and might provide more accurate genetic counseling for this family.
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Schizophrenic Psychosis Symptoms in a Background of Mild-To-Moderate Carnitine Palmitoyltransferase II Deficiency: A Case Report. REPORTS 2020. [DOI: 10.3390/reports3040031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Schizophrenia is a multifaceted mental illness characterized by cognitive and neurobehavioral abnormalities. Carnitine palmitoyltransferase II (CPT II) deficiency is a metabolic disorder resulting in impaired transport of long-chain fatty acids from the cytosol to the mitochondrial inner membrane, where fatty acid β-oxidation takes place. Here, we present an interesting clinical case of an adolescent male that presented with psychosis and a history of mild-to-moderate CPT II deficiency. To identify germline genetic variation that may contribute to the phenotypes observed, we performed whole-exome sequencing on DNA from the proband, unaffected fraternal twin, and biological parents. The proband was identified to be homozygous for the p.Val368Ile and heterozygous for the p.Met647Val variant in CPT2. Each of these variants are benign on their own; however, their combined effect is unclear. Further, variation was identified in the dopamine β-hydroxylase (DBH) gene (c.339+2T>C), which may contribute to decreased activity of DBH; however, based on the patient’s presentation, severe DBH deficiency is unlikely. In conclusion, the variants identified in this study do not clearly explain the observed patient phenotypes, indicating that the complex phenotypes are likely caused by an interplay of genetic and environmental factors that warrant further investigation.
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Binaafar S, Razmara E, Mahdieh N, Sahebjame H, Tavasoli AR, Garshasbi M. A novel missense variant in GPT2 causes non-syndromic autosomal recessive intellectual disability in a consanguineous Iranian family. Eur J Med Genet 2020; 63:103853. [PMID: 31978613 DOI: 10.1016/j.ejmg.2020.103853] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Revised: 12/15/2019] [Accepted: 01/17/2020] [Indexed: 12/28/2022]
Abstract
Intellectual disability (ID) affects 1-3% of the general population worldwide. Genetic factors play an undeniable role in the etiology of Non-Syndromic Intellectual disability (NS-ID). Nowadays, whole-exome sequencing (WES) technique is used frequently to identify the causative genes in such heterogeneous diseases. Herein, we subjected four patients with initial diagnostics of NS-ID in a consanguineous Iranian family. To find the possible genetic cause(s), Trio-WES was performed on the proband and his both healthy parents. Sanger sequencing was performed to confirm the identified variant by WES and also investigate whether it co-segregates with the patients' phenotype in the family. Using several online in-silico predictors, the probable impacts of the variant on structure and function of GPT2 protein were predicted. A novel variant, c.266A>G; p.(Glu89Gly), in exon 3 of GPT2 (NM_133443.3) was identified using Trio-WES. The candidate variant was also verified by Sanger sequencing. All affected members showed the common clinical features suffering from a non-progressive mild-to-severe ID. Also, different clinical observations compared to previously reported cases such as no facial features, no obvious structural malformations, ability to speak but with difficulty, and lack of any morphological defects were noted for the first time in this family. The c.266A>G; p.(Glu89Gly) variant reported here is the sixth variant identified up to now in the GPT2 gene, to be associated with NS-ID. Our data support the potential malfunction of the substituted GPT2 protein resulted from the novel variant, however, we strongly suggest confirming this finding more by doing functional analysis.
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Affiliation(s)
- Sima Binaafar
- Cardiogenetic Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Ehsan Razmara
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC, 3800, Australia
| | - Nejat Mahdieh
- Cardiogenetic Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Hamidreza Sahebjame
- Department of Biology, Faculty of Basic Science, Gonbad Kavous University, Gonbad Kavous, Golestan, Iran
| | - Ali Reza Tavasoli
- Myelin Disorders Clinic, Pediatric Neurology Division, Children's Medical Center, Pediatrics Center of Excellence, Tehran University of Medical Sciences, Tehran, Iran
| | - Masoud Garshasbi
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
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Zare-Abdollahi D, Bushehri A, Alavi A, Dehghani A, Mousavi-Mirkala M, Effati J, Miratashi SAM, Dehani M, Jamali P, Khorram Khorshid HR. MFSD8 gene mutations; evidence for phenotypic heterogeneity. Ophthalmic Genet 2019; 40:141-145. [PMID: 31006324 DOI: 10.1080/13816810.2019.1592200] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Cone-rod dystrophies are a group of genetically and phenotypically heterogeneous inherited degenerative retinal diseases primarily affecting macular and cone system function. MFSD8 loss-of-function variants are mainly related to the variant late-infantile neuronal ceroid lipofuscinoses which present with progressive motor and mental regression in combination with seizures, ataxia, and visual impairment. MATERIAL AND METHODS Clinical examination and genomic DNA extraction were collected from two unrelated Iranian families presenting with autosomal recessive cone-rod dystrophy. The candidate disease-causing variant was screened with whole-exome sequencing and bioinformatics analyses. Sanger sequencing was used for validation and co-segregation analysis. RESULTS Two previously reported variants (c.1361T>C; p.M454T and c.1235C>T; p.P412L) and in a compound heterozygous pattern in one family and a homozygous variant (c.1361T>C; p.M454T) identical to one of the variants in the first family in MFSD8 gene were identified. Both confirmed by Sanger sequencing and co-segregated with disease status. CONCLUSIONS Here and for the first time, we reported on two previously variant late-infantile neuronal ceroid lipofuscinoses-associated variants in MFSD8 but in association with a form of cone-rod dystrophy known as non-syndromic macular dystrophy with central cone involvement. Our results support this concept that variant late-infantile neuronal ceroid lipofuscinoses and non-syndromic macular dystrophy with central cone involvement are not different disease entities, but rather allelic diseases and phenotypic variants of the same mutation. Consideration of the milder MFSD8 phenotypes is important against the potentially severe consequences of life-threatening conditions associated with MFSD8 mutations in order to prevent the danger of misdiagnosis as well as the accuracy of genetic counseling.
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Affiliation(s)
- Davood Zare-Abdollahi
- a Genetics Research Center , University of Social Welfare and Rehabilitation Sciences , Tehran , Iran
| | - Ata Bushehri
- a Genetics Research Center , University of Social Welfare and Rehabilitation Sciences , Tehran , Iran
| | - Afagh Alavi
- a Genetics Research Center , University of Social Welfare and Rehabilitation Sciences , Tehran , Iran
| | - Alireza Dehghani
- b Department of Ophthalmology , Eye Research Center, Isfahan University of Medical Sciences , Isfahan , Iran
| | | | - Jalil Effati
- d Meybod Genetic Research Center, State Welfare Organization of Yazd , Yazd , Iran
| | | | - Mohammad Dehani
- a Genetics Research Center , University of Social Welfare and Rehabilitation Sciences , Tehran , Iran
| | - Payman Jamali
- f Shahrood Genetic Counseling Center , Welfare Office , Semnan , Iran
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