Selective screening and molecular characteristics of Russian patients with Pompe disease

Introduction. Pompe disease (PD) or type II glycogenosis is a rare multisystem hereditary accumulation disease caused by a deficiency of the enzyme acid maltase (acid alpha-1,4-glucosidase), which leads to reduced activity to the accumulation of glycogen in various organs and tissues of the body. The aim of the study is to develop a high-performance method of early biochemical diagnosis of PD and optimization of its molecular genetic diagnosis. Materials and methods. The characteristics of the relative frequencies and spectrum of the detected mutations were studied using a sample of 7670 patients with suspected Pompe disease admitted to the National Medical Research Center of Children’s Health of the Ministry of Health of Russia as part of the selective screening, as well as eight patients with PD, whose laboratory diagnosis was made outside the framework of this selective screening. Results. As a result of selective screening of PD in Russian patients from high-risk groups, the detectability was 0.47%. PD’s clinical and age characteristics in both children and adults are described. The relative frequencies are calculated, and the spectrum of 47 pathogenic variants of the GAA gene responsible for the occurrence and development of Pompe disease in 44 patients is characterized. Seventeen new mutations of the GAA gene, unknown previously, have been identified and described, adding 2.7% to the HGMD database. Conclusion. Optimization of the algorithm of molecular diagnosis of Pompe disease in Russian patients is proposed.

Late Onset Pompe Disease with Novel Mutations and Atypical Phenotypes

Background: Late onset Pompe disease (LOPD) is rare and generally manifests predominantly as progressive limb girdle muscle weakness. It is linked to the pathogenic mutations in GAA gene, which leads to glycogen accumulation in various tissues. Materials and methods: We describe the unusual clinical, biochemical, histopathological and genetic characteristics of 5 cases of LOPD. Results: The first case had progressive anterior horn cell like disease (AHCD) that evolved later to classical limb girdle syndrome and respiratory failure, the second patient had rigid spine syndrome with gastrointestinal manifestations, the third had limb girdle weakness superimposed with episodic prolonged worsening and respiratory failure, the fourth had large fibre sensory neuropathy without primary muscle involvement and the fifth presented with classical limb girdle muscle weakness. Two homozygous missense mutations c.1461C > A (p.Phe487Leu) and c.1082C > T (p.Pro361Leu) in the GAA gene were identified in case 1 and 2 respectively. Case 3 was compound heterozygous with inframe c.1935_1940del (p.Val646_Cys647del) and an intronic splice effecting variant c.-32-13T > G. Compound heterozygous missense variants c.971C > T (p.Pro324Leu) and c.794G > A (p.Ser265Asn) were identified in case 4. Case 5 had a frameshift insertion c.1396dupG (p.Val466GlyfsTer40) and a synonymous splice affecting variant c.546G > T(p.Thr182=). Conclusion: We are describing for the first time from India on LOPD with unusual phenotypes identified. A high degree of clinical suspicion and diagnosing rare phenotypes of Pompe disease is imperative to consider early initiation of Enzyme Replacement Therapy (ERT).

Pharmacological Chaperone Therapy for Pompe Disease

Pompe disease (PD), a lysosomal storage disease, is caused by mutations of the GAA gene, inducing deficiency in the acid alpha-glucosidase (GAA). This enzymatic impairment causes glycogen burden in lysosomes and triggers cell malfunctions, especially in cardiac, smooth and skeletal muscle cells and motor neurons. To date, the only approved treatment available for PD is enzyme replacement therapy (ERT) consisting of intravenous administration of rhGAA. The limitations of ERT have motivated the investigation of new therapies. Pharmacological chaperone (PC) therapy aims at restoring enzymatic activity through protein stabilization by ligand binding. PCs are divided into two classes: active site-specific chaperones (ASSCs) and the non-inhibitory PCs. In this review, we summarize the different pharmacological chaperones reported against PD by specifying their PC class and activity. An emphasis is placed on the recent use of these chaperones in combination with ERT.

Molecular study of Pompe disease in Egyptian infants

Background Pompe disease (PD) is a serious genetic disorder caused by deficiency of acid α-glucosidase (GAA) and subsequent glycogen accumulation inside lysosomes. This study included a cohort of 5 Egyptian infants (1–8 months old) with far lower than average normal GAA activity and clinical signs of PD in 4 of the 5 cases. The fifth case was discovered by newborn screening (NBS). Molecular analysis of the GAA gene was performed to confirm the diagnosis and identify the underlying mutation. Results The study identified the causative mutations [c.1193T > C (p.Leu398Pro), c.1134C > G (p.Tyr378*) & c.1431del (p.Ile477Metfs*43)] in 4 cases. However, molecular analysis reversed the expected pathologic state in the fifth infant, where his reduced enzymatic activity was related to the presence of pseudodeficiency allele c.868A > G (p.Asn290Asp) in addition to heterozygous disease-causing mutation c.2238G > C (p.Trp746Cys). Conclusion This study presents the first molecular analysis of GAA gene in Egypt and has thrown some light on the importance of PD molecular diagnosis to provide precise diagnosis and enable therapeutic commencement in affected subjects.

Complex Transposon Insertion as a Novel Cause of Pompe Disease

Pompe disease (OMIM#232300) is an autosomal recessive lysosomal storage disorder caused by mutations in the GAA gene. According to public mutation databases, more than 679 pathogenic variants have been described in GAA, none of which are associated with mobile genetic elements. In this article, we report a novel molecular genetic cause of Pompe disease, which could be hardly detected using routine molecular genetic analysis. Whole genome sequencing followed by comprehensive functional analysis allowed us to discover and characterize a complex mobile genetic element insertion deep in the intron 15 of the GAA gene in a patient with infantile onset Pompe disease.

Correlation of GAA Genotype and Acid-α-Glucosidase Enzyme Activity in Hungarian Patients with Pompe Disease

Pompe disease is caused by the accumulation of glycogen in the lysosomes due to a deficiency of the lysosomal acid-α-glucosidase (GAA) enzyme. Depending on residual enzyme activity, the disease manifests two distinct phenotypes. In this study, we assess an enzymatic and genetic analysis of Hungarian patients with Pompe disease. Twenty-four patients diagnosed with Pompe disease were included. Enzyme activity of acid-α-glucosidase was measured by mass spectrometry. Sanger sequencing and an MLPA of the GAA gene were performed in all patients. Twenty (83.33%) patients were classified as having late-onset Pompe disease and four (16.66%) had infantile-onset Pompe disease. Fifteen different pathogenic GAA variants were detected. The most common finding was the c.-32-13 T > G splice site alteration. Comparing the α-glucosidase enzyme activity of homozygous cases to the compound heterozygous cases of the c.-32-13 T > G disease-causing variant, the mean GAA activity in homozygous cases was significantly higher. The lowest enzyme activity was found in cases where the c.-32-13 T > G variant was not present. The localization of the identified sequence variations in regions encoding the crucial protein domains of GAA correlates with severe effects on enzyme activity. A better understanding of the impact of pathogenic gene variations may help earlier initiation of enzyme replacement therapy (ERT) if subtle symptoms occur. Further information on the effect of GAA gene variation on the efficacy of treatment and the extent of immune response to ERT would be of importance for optimal disease management and designing effective treatment plans.

In Silico Analysis of Nonsynonumus Single Nucleotide Polymorphisms(nsSNPs) in Human GAAGene

Background: Pompe disease an autosomal recessive lysosomal disorder caused by deficiency of acid alpha-glucosidase (GAA) gene, leading to a progressive accumulation of glycogen in lysosomes in skeletal, cardiac, and smooth muscles. GAA gene provides instructions for producing an enzyme called acid alpha-glucosidase. This enzyme is active in lysosomes, which are structures that serve as recycling centers within cells. Acid alpha-glucosidase normally breaks down glycogen into a simpler glucose. Glucose is the main energy source for most cells. Material and Methods: Information regarding GAA SNPs was obtained from National Center for Biological Information (NCBI) SNPs database, November 2020.The SNPs and the related ensembles proteins (ESNP) were obtained from the SNPs database and UniprotKB database. Analysis of Functional Consequences of coding nonsynonoumus single nucleotide polymorphisms (nsSNPs) by Sequence Homology Based Method wee done using SIFTS, Provean and Polyphen-2 software. Protein stability was predicted using I-Mutant and Mupro software. The pathogenicity and relation of the mutation to disease association was predicted by SNP&GO and PHD software. For the effect of the mutation on the protein structure and function, ProjectHope, Chimera and Raptor X were used. For the association, co-expression and shared domains of the gene to other genes GeneMANIA software was used. Results: GAA gene had254 SNPS WITH 179 SNPS IN CODING REGION AND 75 IN NON CODINGregion, nsSNPs were analyzed by SIFT software, and only 64 nsSNPs were predicted to be deleterious while 11 were tolerated. Using Provean software 53nsSNPs were deleterious and 11nsSNPs were neutral. These deleterious SNPs were analyzed using polyphen_2 software to predict the damaging SNPs, the damaging SNPs were 53 nsSNPs. Using I-mutant software for evaluation of the degree of stability due to mutation. The present study predicted 43 nsSNPsto decrease the stability of the protein, while only 10 SNPs had increased in the stability of the protein. For Mupro software52 nsSNPs decrease the stability of protein and only one SNP increase the stability of protein. For more confirmation for the mutation the study used PHD software in which 46nsSNPs were reported as a disease related, while 7SNPs were reported as neutral. SNP &GO software was also used, it predicted 37 SNPs as disease related, while 16 SNPs were reported as neutral. For ProjectHope the 20 damaging nsSNPs from previous software gave effect on the function and structure of the protein, Conclusion: The study concluded that there were 20 nsSNPs predicted to be damaging to the protein (rs1800307 rs18003122 rs28937909 rs61736895 rs121907937 rs121907938 rs121907945 rs139009731 rs142752477 rs144016984 rs147327209 rs148842275 rs202095215 rs369098202 rs372486238 rs372604133 rs374143224 rs374470794 rs374687883 rs377544304 ).These results may provide useful information needed to help researchers to use thesensSNPs as biomarkers for Pompe disease .

Pompe Disease Screening in a Sample of Iranian Patients

The reason why the experiments were done: previous studies have shown that the incidence rates vary in different populations. Now we report the preliminary results of the screening study. Pompe disease is a rare but potentially treatable disorder caused by the deficiency of the lysosomal enzyme acid-α-glucosidase (GAA). GAA activity was measured on DBS in 65 patients with undiagnosed myopathies presenting to the hospital of the research setting in Isfahan, Iran, from 2016 to 2017 and then was confirmed by genetic analysis. Of the total of 65 patients, 29 (44.6%) were male, and 36 (55.4%) were female. The mean age of the patients was 29±12.55 years, and their mean age at the disease onset was 17±12.75. Two patients (one male and one female) were diagnosed with a low acid alpha-glucosidase activity. Only one patient (female) showed a compound heterozygotic mutation of the GAA gene (c.-32-13T>G). Early diagnosis of Pompe disease is important for improving the outcome.

Variable Genotype–Phenotype Correlation of Pompe's Disease Caused by a c.2015 G > A (p.Arg672Gln) Mutation in the GAA Gene

Pompe's disease occurs due to an autosomal recessive trait resulting from numerous distinctive mutations in the GAA gene. It manifests as a broad spectrum of clinical phenotypes with progressive weakness that impairs motor and respiratory functions being common for all its forms. Cardiac hypertrophy is a prominent feature of its classic infantile form. To date, the pathogenic variant c.2015G > A (p.Arg672Gln) in exon 14 of the GAA gene has been described in 10 children of different ethnic groups, with variable phenotypic presentations. This work describes three children from two unrelated families of Arab ethnicity who presented with infantile-onset Pompe's disease as a result of a c.2015G > A (p.Arg672Gln) mutation. The clinical course of the children we report was more severe than previous reports. This further emphasizes the lack of a strict genotype–phenotype correlation in regard to the unique c.2015G > A (p.R672Q) mutation that causes Pompe's disease. This information contributes to the knowledge of the phenotypic expression of the specific mutation c.2015G > A (p.Arg672Gln) that causes Pompe's disease.

In Silico Analysis of Nonsynonumus Single Nucleotide Polymorphisms(nsSNPs) in Human GAAGene

Background: Pompe disease an autosomal recessive lysosomal disorder caused by deficiency of acid alpha-glucosidase (GAA) gene, leading to a progressive accumulation of glycogen in lysosomes in skeletal, cardiac, and smooth muscles. GAA gene provides instructions for producing an enzyme called acid alpha-glucosidase. This enzyme is active in lysosomes, which are structures that serve as recycling centers within cells. Acid alpha-glucosidase normally breaks down glycogen into a simpler glucose. Glucose is the main energy source for most cells. Material and Methods: Information regarding GAA SNPs was obtained from National Center for Biological Information (NCBI) SNPs database, November 2020.The SNPs and the related ensembles proteins (ESNP) were obtained from the SNPs database and UniprotKB database. Analysis of Functional Consequences of coding nonsynonoumus single nucleotide polymorphisms (nsSNPs) by Sequence Homology Based Method wee done using SIFTS, Provean and Polyphen-2 software. Protein stability was predicted using I-Mutant and Mupro software. The pathogenicity and relation of the mutation to disease association was predicted by SNP&GO and PHD software. For the effect of the mutation on the protein structure and function, ProjectHope, Chimera and Raptor X were used. For the association, co-expression and shared domains of the gene to other genes GeneMANIA software was used. Results:GAA gene had254 SNPS WITH 179 SNPS IN CODING REGION AND 75 IN NON CODINGregion, nsSNPs were analyzed by SIFT software, and only 64 nsSNPs were predicted to be deleterious while 11 were tolerated. Using Provean software 53nsSNPs were deleterious and 11nsSNPs were neutral. These deleterious SNPs were analyzed using polyphen_2 software to predict the damaging SNPs, the damaging SNPs were 53 nsSNPs. Using I-mutant software for evaluation of the degree of stability due to mutation. The present study predicted 43 nsSNPsto decrease the stability of the protein, While only 10 SNPs had increased in the stability of the protein. For Mupro software52 nsSNPs decrease the stability of protein and only one SNP increase the stability of protein. For more confirmation for the mutation the study used PHD software in which 46nsSNPs were reported as a disease related, while 7SNPs were reported as neutral. SNP &GO software was also used, it predicted 37 SNPs as disease related, while 16 SNPs were reported as neutral. For ProjectHope the 20 damaging nsSNPs from previous software gave effect on the function and structure of the protein, Conclusion: The study concluded that there were 20 nsSNPs predicted to be damaging to the protein (rs1800307 rs18003122 rs28937909 rs61736895 rs121907937 rs121907938 rs121907945 rs139009731 rs142752477 rs144016984 rs147327209 rs148842275 rs202095215 rs369098202 rs372486238 rs372604133 rs374143224 rs374470794 rs374687883 rs377544304 ).These results may provide useful information needed to help researchers to use these nsSNPs as biomarkers for Pompe disease .