Prevalent ALMS1 Pathogenic Variants in Spanish Alstrom Patients.
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SUBMITTER: Bea-Mascato B
PROVIDER: S-EPMC7920446 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:PurposeAlström syndrome (AS) is a rare monogenic autosomal recessively inherited disorder characterized by cone rod dystrophy and multiple organ dysfunction. Mutations in the Alström syndrome 1 (ALMS1) gene have been found to be causative for AS. The purpose of this study was to identify ALMS1 mutations and to assess the clinical features of Chinese patients with AS.MethodsDetailed ocular and laboratory examinations were performed. Peripheral blood samples were collected from patients and their parents. Genomic DNA was extracted with a Qiagen kit. Exons and exon/intron junctions of ALMS1 were amplified with polymerase chain reaction (PCR) and screened for mutations with Sanger sequencing. The results were compared with the ALMS1 transcript to exclude polymorphisms and confirm pathogenic mutations.ResultsSeven patients from five unrelated non-consanguineous families were diagnosed with AS. All patients had cone rod dystrophy with impaired visual acuity, photophobia, and nystagmus. Other clinical features, including sensorineural hearing loss, truncal obesity, insulin resistance, type 2 diabetes mellitus, renal and hepatic dysfunction, hyperlipidemia, hypothyroidism, mental retardation, acanthosis nigricans, and scoliosis, were present. Sequencing revealed two novel mutations, p.N3150Kfs2X and p.V3154Xfs, in patient 1; one novel mutation, p.N3672Ifs11X, and one previously reported nonsense mutation, p.R3703X, in patient 2; novel mutations p.S2479X and p.R3611Efs7X in patient 3; one novel homozygous mutation, p.S695X, in patients 4 and 5; and two novel mutations, p.H688HfsX and p.Q3147Qfs2X, in patients 6 and 7. These mutations were not present in 100 unrelated healthy Chinese control subjects. The patients' parents were heterozygous carriers of the mutant allele.ConclusionsSeven Chinese patients with AS showed typical ophthalmic features and multiple organ dysfunction. Novel loss of function mutations in the ALMS1 gene are the underlying genetic defects.
| S-EPMC3774572 | biostudies-literature
Project description:The Alstrom syndrome gene (ALMS1) is one of the largest disease associated genes identified today in the human genome and is implicated in cell cycle control, ciliogenesis, endosome recycling and intracellular transport mechanisms. ALMS1 mutations cause Alstrom syndrome, a rare genetic disorder. However, its function is not completely understood. DNA microarray analysis suggested that ALMS1 might be differentially expressed between Hodgkin lymphoma (HL) cells and normal tissues. By using reverse transcription-polymerase chain reaction (RT-PCR) we detected low but variable expression of ALMS1 in HL cell lines with highest expression in KM-H2 cells. Immunofluorescence indicated centrosomal accumulation of ALMS1 protein in HL cells. Knock-down of ALMS1 in KM-H2 cells had no impact on viability or cytotoxic drug sensitivity of these cells. Sequencing of RT-PCR products from HL cell lines identified three variable regions in ALMS1 transcripts that affect exons 2, 13, and 23. One of these variants was characterized by splicing out of exon 13. The other variants are characterized by two alternative 5 prime ends or alternative 3 prime ends. Structure prediction of the corresponding RNAs and proteins suggest that the different transcript variants might affect posttranscriptional regulation and ligand binding.
| S-EPMC5279758 | biostudies-literature
Project description:Alström Syndrome (ALMS), a recessive, monogenic ciliopathy caused by mutations in ALMS1, is typically characterized by multisystem involvement including early cone-rod retinal dystrophy and blindness, hearing loss, childhood obesity, type 2 diabetes mellitus, cardiomyopathy, fibrosis, and multiple organ failure. The precise function of ALMS1 remains elusive, but roles in endosomal and ciliary transport and cell cycle regulation have been shown. The aim of our study was to further define the spectrum of ALMS1 mutations in patients with clinical features of ALMS. Mutational analysis in a world-wide cohort of 204 families identified 109 novel mutations, extending the number of known ALMS1 mutations to 239 and highlighting the allelic heterogeneity of this disorder. This study represents the most comprehensive mutation analysis in patients with ALMS, identifying the largest number of novel mutations in a single study worldwide. Here, we also provide an overview of all ALMS1 mutations identified to date.
| S-EPMC4475486 | biostudies-literature
Project description:Alström syndrome (ALMS) is a rare autosomal recessive multi-organ syndrome considered to date as a ciliopathy and caused by variations in ALMS1. Phenotypic variability is well-documented, particularly for the systemic disease manifestations; however, early-onset progressive retinal degeneration affecting both cones and rods (cone-rod type) is universal, leading to blindness by the teenage years. Other features include cardiomyopathy, kidney dysfunction, sensorineural deafness, and childhood obesity associated with hyperinsulinemia and type 2 diabetes mellitus. Here, we present an unusual and delayed retinal dystrophy phenotype associated with ALMS in a 14-year-old female, with affected cone function and surprising complete preservation of rod function on serial electroretinograms (ERGs). High-throughput sequencing of the affected proband revealed compound heterozygosity with two novel nonsense variations in the ALMS1 gene, including one variant of de novo inheritance, an unusual finding in autosomal recessive diseases. To confirm the diagnosis in the context of an unusually mild phenotype and identification of novel variations, we demonstrated the biallelic status of the compound heterozygous variations (c.[286C > T];[1211C > G], p.[(Gln96*)];[(Ser404*)]). This unique case extends our knowledge of the phenotypic variability and the pathogenic variation spectrum in ALMS patients.
| S-EPMC7472914 | biostudies-literature
Project description:Objective Alström syndrome is an autosomal recessive genetic disease caused by a mutation in the ALMS1 gene. Alström syndrome is clinically characterized by multisystem involvement, including sensorineural deafness, cone-rod dystrophy, nystagmus, obesity, insulin resistance, type 2 diabetes and hypogonadism. The diagnosis is thus challenging for patients without this characteristic set of clinical symptoms. We explored the effectiveness of whole-exome sequencing in the diagnosis of Alström syndrome. Methods A girl with symptoms of Alström syndrome was tested and diagnosed with the disease by whole-exome sequencing. Results Whole-exome sequencing revealed two novel variants, c.6160_6161insAT: p.Lys2054Asnfs*21 (exon 8) and c.10823_10824 delAG:p.Glu 3608Alafs*9 (exon16) in the ALMS1 gene, leading to premature termination codons and the domain of ALMS1 protein. Blood sample testing of her asymptomatic parents revealed them to be heterozygous carriers of the same mutations. Assembly showed that the mutations on both alleles were located in conserved sequences. A review of the ALMS1 gene nonsense mutation status was performed. Conclusion We herein report two novel variants of the ALMS1 gene discovered in a Chinese Alström syndrome patient that expand the mutational spectrum of ALMS1 and provided new insight into the molecular mechanism underlying Alström syndrome. Our findings add to the current knowledge concerning the diagnosis and treatment of Alström syndrome.
| S-EPMC8710367 | biostudies-literature
Project description:Mutations in the human ALMS1 gene cause Alström syndrome (AS), a progressive disease characterized by neurosensory deficits and by metabolic defects including childhood obesity, hyperinsulinemia and Type 2 diabetes. Other features that are more variable in expressivity include dilated cardiomyopathy, hypertriglyceridemia, hypercholesterolemia, scoliosis, developmental delay and pulmonary and urological dysfunctions. ALMS1 encodes a ubiquitously expressed protein of unknown function. To obtain an animal model in which the etiology of the observed pathologies could be further studied, we generated a mouse model using an Alms1 gene-trapped ES cell line. Alms1-/- mice develop features similar to patients with AS, including obesity, hypogonadism, hyperinsulinemia, retinal dysfunction and late-onset hearing loss. Insulin resistance and increased body weight are apparent between 8 and 12 weeks of age, with hyperglycemia manifesting at approximately 16 weeks of age. In addition, Alms1-/- mice have normal hearing until 8 months of age, after which they display abnormal auditory brainstem responses. Diminished cone ERG b-wave response is observed early, followed by the degeneration of photoreceptor cells. Electron microscopy revealed accumulation of intracellular vesicles in the inner segments of photoreceptors, whereas immunohistochemical analysis showed mislocalization of rhodopsin to the outer nuclear layer. These findings suggest that ALMS1 has a role in intracellular trafficking.
| S-EPMC2862911 | biostudies-literature
Project description:Alström syndrome (AS, OMIM ID 203800) is a rare childhood multiorgan disorder, which is widely studied in non-Arab ethnic patients. The clinical and molecular basis of AS and the mode of disease inheritance in consanguineous Arab populations is not well investigated. Therefore, to identify the molecular basis of AS in familial forms, the present study performed whole exome sequencing of 5 AS patients belonging to 2 different Bedouin families from Saudi Arabia. The present study identified the AS causative rare biallelic mutations in ALMS gene:T376S in exon 5 and S909* in exon 8 for family A and an R2721* in exon 10 (R2721*) for family B. ALMS1 targeted genetic sequencing of healthy population controls and family members has confirmed its extremely rare frequency and autosomal recessive mode of inheritance. The truncating mutations S909* and R2721* could cause the loss of CC domains and ALMS motif on C-terminal end of the protein and creates unstable protein, which eventually undergoes intracellular degradation. The premature protein truncating mutations described in our study may eventually provide further insight into the functional domains of the ALMS1 protein and contribute to the understanding of the phenotypic spectrum of AS. Whole exome sequencing based molecular diagnosis is expected to rule out ambiguity surrounding clinical diagnosis of suspected AS cases.
| S-EPMC6933154 | biostudies-literature
Project description:Premature truncation alleles in the ALMS1 gene are a frequent cause of human Alström syndrome. Alström syndrome is a rare disorder characterized by early obesity and sensory impairment, symptoms shared with other genetic diseases affecting proteins of the primary cilium. ALMS1 localizes to centrosomes and ciliary basal bodies, but truncation mutations in Alms1/ALMS1 do not preclude formation of cilia. Here, we show that in vitro knockdown of Alms1 in mice causes stunted cilia on kidney epithelial cells and prevents these cells from increasing calcium influx in response to mechanical stimuli. The stunted-cilium phenotype can be rescued with a 5' fragment of the Alms1 cDNA, which resembles disease-associated alleles. In a mouse model of Alström syndrome, Alms1 protein can be stably expressed from the mutant allele and is required for cilia formation in primary cells. Aged mice developed specific loss of cilia from the kidney proximal tubules, which is associated with foci of apoptosis or proliferation. As renal failure is a common cause of mortality in Alström syndrome patients, we conclude that this disease should be considered as a further example of the class of renal ciliopathies: wild-type or mutant alleles of the Alström syndrome gene can support normal kidney ciliogenesis in vitro and in vivo, but mutant alleles are associated with age-dependent loss of kidney primary cilia.
| S-EPMC1761047 | biostudies-literature
Project description:Alström syndrome (AS) is characterised by metabolic deficits, retinal dystrophy, sensorineural hearing loss, dilated cardiomyopathy and multi-organ fibrosis. Elucidating the function of the mutated gene, ALMS1, is critical for the development of specific treatments and may uncover pathways relevant to a range of other disorders including common forms of obesity and type 2 diabetes. Interest in ALMS1 is heightened by the recent discovery of its involvement in neonatal cardiomyocyte cell cycle arrest, a process with potential relevance to regenerative medicine. ALMS1 encodes a ~?0.5 megadalton protein that localises to the base of centrioles. Some studies have suggested a role for this protein in maintaining centriole-nucleated sensory organelles termed primary cilia, and AS is now considered to belong to the growing class of human genetic disorders linked to ciliary dysfunction (ciliopathies). However, mechanistic details are lacking, and recent studies have implicated ALMS1 in several processes including endosomal trafficking, actin organisation, maintenance of centrosome cohesion and transcription. In line with a more complex picture, multiple isoforms of the protein likely exist and non-centrosomal sites of localisation have been reported. This review outlines the evidence for both ciliary and extra-ciliary functions of ALMS1.
| S-EPMC6327082 | biostudies-other
Project description:Background: Alström syndrome (AS) is a very rare childhood disorder characterized by cardiomyopathy, progressive hearing loss and blindness. Inherited genetic variants of ALMS1 gene are the known molecular cause of this disease. The objective of this study was to characterize the genetic basis and understand the genotype-phenotype relationship in Saudi AS patients. Methods: Clinical phenotyping and whole-exome sequencing (WES) analysis were performed on six AS patients belonging to two unrelated consanguineous Saudi families. Sanger sequencing was performed to determine the mode of inheritance of ALMS1 variant in first-degree family relatives and also to ensure its rare prevalence in 100 healthy population controls. Results: We identified that Alström patients from both the families were sharing a very rare ALMS1, 3'-splice site acceptor (c.11873-2 A>T) variant, which skips entire exon-19 and shortens the protein by 80 amino acids. This disease variant was inherited by AS patients in autosomal recessive mode and is not yet reported in any population-specific genetic databases. AS patients carrying this mutation showed heterogeneity in clinical presentations. Computational analysis of the mutant centroid structure of ALMS1 mRNA revealed that exon-19 skipping enlarges the hairpin loop and decreases the free energy, eventually affecting its folding pattern, stability, and function. Hence, we propose c.11873-2A as an AS causative potential founder mutation in Saudi Arabia because it is found in two families lacking a common lineage. Conclusions: We conclude that WES analysis potentially helps in clinical phenotyping, early diagnosis, and better clinical management of Alström patients showing variable clinical expressivity.
| S-EPMC8107379 | biostudies-literature