Mutation spectrum of α-Galactosidase gene in Japanese patients with Fabry disease

Pilot study of newborn screening for six lysosomal diseases in Brazil

BACKGROUND

Lysosomal diseases (LDs) are progressive life-threatening disorders that are usually asymptomatic at birth. Specific treatments are available for several LDs, and early intervention improves patient's outcomes. Thus, these diseases benefit from newborn screening (NBS). We have performed a pilot study for six LDs in Brazil by tandem mass spectrometry.

METHODS

Dried blood spot (DBS) samples of unselected newborns were analyzed by the Neo-LSD™ kit (Perkin-Elmer) by MS/MS. Samples with low enzyme activity were submitted to the evaluation of specific biomarkers by ultra-performance liquid chromatography tandem-mass spectrometry as the second-tier, and were analyzed by a next-generation sequencing (NGS) multi-gene panel as the third-tier. All tests were performed in the same DBS sample.

RESULTS

In 20,066 newborns analyzed, 15 samples showed activity of one enzyme below the cutoff. Two newborns had biochemical and molecular results compatible with Fabry disease, and five newborns had biochemical results and pathogenic variants or variants of unknown significance (VUS) in GAA.

CONCLUSIONS

This study indicates that the use of enzyme assay as the first-tier test gives an acceptably low number of positive results that requires second/third tier testing. The possibility to run all tests in a DBS sample makes this protocol applicable to large-scale NBS programs.

The Interplay of Glycosaminoglycans and Cysteine Cathepsins in Mucopolysaccharidosis

Mucopolysaccharidosis (MPS) consists of a group of inherited lysosomal storage disorders that are caused by a defect of certain enzymes that participate in the metabolism of glycosaminoglycans (GAGs). The abnormal accumulation of GAGs leads to progressive dysfunctions in various tissues and organs during childhood, contributing to premature death. As the current therapies are limited and inefficient, exploring the molecular mechanisms of the pathology is thus required to address the unmet needs of MPS patients to improve their quality of life. Lysosomal cysteine cathepsins are a family of proteases that play key roles in numerous physiological processes. Dysregulation of cysteine cathepsins expression and activity can be frequently observed in many human diseases, including MPS. This review summarizes the basic knowledge on MPS disorders and their current management and focuses on GAGs and cysteine cathepsins expression in MPS, as well their interplay, which may lead to the development of MPS-associated disorders.

In Vivo Delivery of Therapeutic Molecules by Transplantation of Genome-Edited Induced Pluripotent Stem Cells

Human induced pluripotent stem cells (iPSCs) have already been used in transplantation therapies. Currently, cells from healthy people are transplanted into patients with diseases. With the rapid evolution of genome editing technology, genetic modification could be applied to enhance the therapeutic effects of iPSCs, such as the introduction of secreted molecules to make the cells a drug delivery system. Here, we addressed this possibility by utilizing a Fabry disease mouse model, as a proof of concept. Fabry disease is caused by the lack of α-galactosidase A (GLA). We previously developed an immunotolerant therapeutic molecule, modified α-N-acetylgalactosaminidase (mNAGA). We confirmed that secreted mNAGA from genome-edited iPSCs compensated for the GLA activity in GLA-deficient cells using an in vitro co-culture system. Moreover, iPSCs transplanted into Fabry model mice secreted mNAGA and supplied GLA activity to the liver. This study demonstrates the great potential of genome-edited iPSCs secreting therapeutic molecules.

Cardiac involvement in Fabry disease - A non-invasive assessment and the role of specific therapies

Fabry disease is an X-linked inherited metabolic disorder due to the pathogenic mutation of the GLA gene, which codes lysosomal enzyme alpha-galactosidase A. The resultant accumulation of glycosphingolipids causes various systemic symptoms in childhood and adolescence, and major organ damage in adulthood. Cardiac involvement is important as the most frequent cause of death in Fabry disease patients. Progressive left ventricular hypertrophy with varying degrees of contractile dysfunction as well as conduction abnormalities and arrhythmias are typical cardiac features, and these findings can be evaluated in detail via non-invasive modalities, such as an electrocardiogram, echocardiography and cardiac magnetic resonance. In addition, specific therapies of enzyme replacement therapy and pharmacological chaperone therapy are available, and their beneficial effects on cardiac involvement have been reported. This minireview highlights recent evidence concerning non-invasive modalities for assessing cardiac involvement in Fabry disease and the effects of enzyme replacement therapy and pharmacological chaperone therapy on the findings of those modalities.

Screening for Fabry disease among male patients on hemodialysis in Awaji Island

BACKGROUND

Fabry disease (FD) manifests decreased α-galactosidase A (α-Gal A) activity and multiorgan damage. There are some undiagnosed cases of the condition among patients on dialysis. The prevalence of FD may also vary with the region.

METHODS

Among 227 male patients undergoing maintenance hemodialysis in Awaji Island, a remote island in Japan, 201 (88.5%) were included in this study. Patients with α-Gal A activity <5.0 pmol/hr/disk proceeded to secondary screening. Patients with positive secondary screening underwent further genetic analysis.

RESULTS

The number of patients with a family history of cardiac, cerebrovascular, and kidney diseases was 31 (15.4%), 23 (11.4%), and 31 (15.4%) patients, respectively. Although three patients (1.5%) had low α-Gal A activity, none of them was positive in the secondary screening.

CONCLUSION

We could not identify any male hemodialysis patient with FD in Awaji Island, even though some patients had a family history of kidney and cardiovascular diseases. This article is protected by copyright. All rights reserved.

Novel α-galactosidase A gene mutation in a Chinese Fabry disease family: A case report

BACKGROUND

Fabry disease (FD) is a rare X-linked lysosomal storage disease caused by a deficiency of the enzyme α-galactosidase A.

CASE SUMMARY

Herein, we analyzed a four-generation Chinese family. The proband is a 57-year-old woman who was diagnosed with left ventricular hypertrophy and atrial fibrillation 7 years ago. Echocardiography showed an end-diastolic diameter of the interventricular septum of 19.9 mm, left ventricular end-diastolic diameter of 63.1 mm, and moderate-to-severe mitral regurgitation. Cardiac magnetic resonance indicated an enlarged left heart and right atrium, decreased left ventricular systolic and diastolic function, a left ventricular ejection fraction of 20%, and thickening of the left ventricular septum. In March 2019, gene and enzyme activity tests confirmed the diagnosis of FD. Her son was diagnosed with FD after gene and enzyme activity assay, and was prescribed agalsidase-β for enzyme replacement therapy in July 2020. Two sisters of the proband were also diagnosed with FD by genetic testing. Both of them had a history of atrial fibrillation.

CONCLUSION

A novel mutation was identified in a Chinese family with FD, in which the male patient had a low level of enzyme activity, early-onset, and severe organ involvement. Comprehensive analysis of clinical phenotype genetic testing and enzyme activity testing helped in the diagnosis and treatment of this FD family.

Fabry disease screening in high-risk populations in Japan: a nationwide study

Background

Fabry disease (FD) is a X-linked inherited disorder caused by mutations in the GLA gene, which results in the deficiency of α-galactosidase A (α-Gal A). This leads to the progressive accumulation of metabolites, which can cause multisystemic dysfunction. A recent screening study among neonates reported an increase in the incidence of FD, and numerous FD patients remain undiagnosed or even misdiagnosed. Therefore, this study aimed to identify patients with FD by performing high-risk screening in 18,135 individuals, enrolled from October 2006 to March 2019, with renal, cardiac, or neurological manifestations from all prefectures in Japan. A total of 601 hospitals participated in this study.

Results

Low α-Gal A activity was detected in 846 individuals, with 224 of them diagnosed with FD by GLA sequencing. Cases with a family history of FD (n = 64) were also subjected to sequencing, without α-Gal A assay, as per individual request, and 12 of them were diagnosed with a variant of FD. A total of 236 patients with FD (97 males and 139 females) were identified from among 18,199 participants. A total of 101 GLA variants, including 26 novel variants, were detected in the 236 patients with FD from 143 families, with 39 amenable variants (39%) and 79 of the 236 patients (33%) suitable for migalastat treatment.

Conclusions

From among 18,199 participants, 101 GLA variants, including 26 novel variants, were identified in the 236 patients with FD from 143 families. Migalastat was identified as a suitable treatment option in 33% of the patients with FD and 39% of the GLA variants were detected as amenable. Therefore, the simple screening protocol using dried blood spots that was performed in this study could be useful for early diagnosis and selection of appropriate treatments for FD in high-risk and underdiagnosed patients with various renal, cardiac, or neurological manifestations.

A case of latent heterozygous Fabry disease in a female living kidney donor candidate

A 52-year-old woman had been found to have hematuria at her annual checkup 5 years in a row. She hoped to donate her kidney to her husband, so we performed a percutaneous kidney biopsy at our department. It was difficult for us to detect apparent abnormalities under a light microscopic examination, and she was determined to meet the eligibility criteria for living kidney transplantation. However, the sample for electron microscopy was not evaluated before kidney donation. She subsequently underwent living kidney transplantation as a donor. A 1-h biopsy revealed swelling and obvious vacuolation of the glomerular podocytes, which were characteristic of Fabry disease. Her medical history and examinations were reviewed. No findings or episodes were observed. Pre-donation electronmicroscopy revealed numerous zebra bodies in the podocytes. A definite diagnosis of heterozygous Fabry disease was made based on the GLA gene mutation despite the normal range of leukocyte α-Gal A activity. Based on the pathological deposition of GL-3, chaperone therapy was initiated to suppress the progression of organ damage. In this case, we could not confirm a diagnosis of Fabry disease despite performing a renal biopsy prior to kidney donation. Kidney donor candidates may sometimes have factors that cannot be assumed based on medical or family history. Thus, it is important to perform a renal biopsy before kidney donation when necessary, and to always conduct a detailed evaluation including electron microscopy.

Newborn screening for Fabry disease in the western region of Japan

Newborn screening (NBS) for Fabry disease (FD) is the best way to detect FD early prior to presentation of symptoms and is currently implemented in Taiwan and several states such as Illinois, Missouri, and Tennessee in the United States of America. In this report, we provide data from the first large-scale NBS program for FD in Japan. From August 2006 to December 2018, 599,711 newborns were screened; 26 variants, including 15 pathogenic variants and 11 variants of uncertain significance (VOUS; including eight novel variants), were detected in 57 newborns. Twenty-six male and 11 female newborns with pathogenic variants were diagnosed as hemizygous and heterozygous patients, respectively. Thirteen male and seven female newborns with VOUS were diagnosed as potential hemizygous and potential heterozygous patients, respectively. At the most recent follow up, three of 26 hemizygous patients had manifested symptoms and were receiving enzyme replacement therapy. The other patients were being followed up by clinicians. The frequency of FD (pathogenic variants + VOUS) in this study was estimated to be 1:7683, whereas that of patients with pathogenic variants was 1:11,854. In the future, the NBS system for FD may contribute to the detection of newborns not presenting manifestations related to FD and adults who have or have not developed manifestations related to FD.

Future clinical and biochemical predictions of Fabry disease in females by methylation studies of the GLA gene

Fabry disease is an X-linked lysosomal storage disorder caused by a deficiency of α-galactosidase A (α-gal A). The clinical variability of the phenotypes of Fabry disease in females is still poorly understood. The degree of aberrant methylation of non-mutated alleles is thought to have significant effects on X-chromosome inactivation (XCI). We previously reported that one heterozygous Fabry female showing classical phenotypes had complete methylation of the non-mutated allele of the GLA gene. In this report, we summarized 36 heterozygous females with a clinical severity score based on the FAbry STabilization indEX (FASTEX). We measured their α-gal A activity and plasma/ serum globotriaosylsphingosine (lyso-Gb3) accumulation and performed electron microscopy of skin biopsies. We analyzed the methylation-sensitive restriction enzyme sites throughout the GLA gene, including the 5’UTR, and found a single SacII site and multiple HhaI and HpaII sites aggregated in exon 1 and the 5’UTR. One HpaII sequence in exon 7 was also detected as a methylation-sensitive site. With methylation-sensitive restriction enzymes, methylated and non-methylated alleles could be separated, and the ratio of the methylation was quantified. We found a clear correlation between the severity of the phenotype and lyso-Gb3 accumulation for heterozygous Fabry disease in females. Methylation of the non-mutated allele was also proportionately correlated to the clinical severity score measured by FASTEX.

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We summarized 36 heterozygous Japanese Fabry females with their clinical severity score.

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We had detected methylation-sensitive restriction enzyme sites in exon 7 along with exon 1 and 5`UTR.

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A clear correlation of patients’ FASTEX scores, sphingolipids accumulations and dysmethylation of the GLA gene was detected.