Compound heterozygous pathogenic variants in the GALC gene cause infant-onset Krabbe disease

Krabbe disease (KD) is an infantile neurodegenerative disorder resulting from pathogenic variants in the GALC gene which causes accumulation of the toxic sphingolipid psychosine. GALC variants are associated with increased risk of Lewy body diseases (LBD), an umbrella term for age-associated neurodegenerative diseases in which the protein α-synuclein aggregates into Lewy bodies. To explore whether α-synuclein in KD has pathological similarities to that in LBD, we compared post-mortem KD tissue to that of infant control cases and identified alterations to α-synuclein localisation and expression of modifications associated with LBD. To determine whether α-synuclein in KD displayed pathogenic properties associated with LBD we evaluated its seeding capacity using the real-time quaking-induced conversion assay. Strikingly, seeded aggregation of α-synuclein resulted in the formation of fibrillar aggregates similar to those observed in LBD, confirming the prion-like capacity of KD-derived α-synuclein. These observations constitute the first report of prion-like α-synuclein in the brain tissue of infants and challenge the putative view that α-synuclein pathology is merely an age-associated phenomenon, instead suggesting it can result from alterations to biological processes such as sphingolipid homeostasis. Our findings have important implications for understanding the mechanisms underlying Lewy body formation in LBD.

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Molecular diagnostics of the Krabbe disease in Russian children

L.O. Badalyan Neurological Journal ◽

10.17816/2686-8997-2020-1-01-21-28 ◽

2020 ◽

Vol 1 (1) ◽

pp. 21-28

Author(s):

Alexander A. Pushkov ◽

Nataliya N. Mazanova ◽

Lyudmila M. Kuzenkova ◽

Nataliya V. Zhurkova ◽

Oksana V. Globa ◽

...

Keyword(s):

Enzyme Activity ◽

Molecular Diagnostics ◽

High Efficiency ◽

Molecular Genetic ◽

Krabbe Disease ◽

Control Group ◽

Laboratory Diagnostics ◽

Lysosomal Storage ◽

Pathogenic Variants ◽

Galc Gene

Introduction. Krabbe disease (KD) is the lysosomal storage disease developed due to the decline of the galactocerebrosidase activity associated with mutations in the GALC gene. It leads to the development of oligodendrocytes and lemmocytes (Schwann cells) myelin-forming dysfunction. Nowadays the only possible treatment of KD is hemopoietic cell transplantation which should be performed before the manifestation of any signs of disease. That is why laboratory diagnostics has special significance. The aim of the study. To elaborate the algorithm of a molecular diagnostics of the Krabbe disease (KD) in Russian children. Material and methods. 190 patients were diagnosed for the exclusion of KD during the period from 2012 to 2019. In all cases, there was measured a galactocerebrosidase activity in dry blood spots. In cases with the declined enzyme activity, there was performed a further search of pathogenic variants in the GALC gene. The concentration of glycosyl sphingosine (Lyso-GL1) biomarker was measured in 90 patients included in the study since 2016. Results. The enzyme activity was decreased in all patients in comparison with the control group (0.330.05; 2.950.24 mol/l/h, (p0.001; CI: 95%) in 9 patients. Also, we revealed an increased concentration of Lyso-GL1 biomarker in matched controls (12.501.57 ng/ml; 1.80.33 ng/ml, (p0.005; CI: 95%) in 5 patients. During molecular genetic testing of KD, three novel pathogenic variants of the GALC gene were revealed in 3 out of 9 patients: c.265-2AG, c.1036del and c.2037_2040del. Conclusion. The Lyso-GL1 concentration measurement can be used as an additional diagnostics method of KD. The high efficiency of the presented algorithm for the KD diagnostics in Russian children is presented.

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Advances in the Diagnosis and Treatment of Krabbe Disease

International Journal of Neonatal Screening ◽

10.3390/ijns7030057 ◽

2021 ◽

Vol 7 (3) ◽

pp. 57

Author(s):

David A Wenger ◽

Paola Luzi ◽

Mohammad A. Rafi

Keyword(s):

Newborn Screening ◽

Autosomal Recessive ◽

Cultured Cells ◽

Krabbe Disease ◽

Hematopoietic Stem ◽

Pathogenic Variants ◽

Second Tier ◽

Galc Gene ◽

Hydrolysis Of

Krabbe disease is an autosomal recessive leukodystrophy caused by pathogenic variants in the galactocerebrosidase (GALC) gene. GALC activity is needed for the lysosomal hydrolysis of galactosylceramide, an important component of myelin. While most patients are infants, older patients are also diagnosed. Starting in 1970, a diagnosis could be made by measuring GALC activity in leukocytes and cultured cells. After the purification of GALC in 1993, the cDNA and genes were cloned. Over 260 disease-causing variants as well as activity lowering benign variants have been identified. While some pathogenic variants can be considered “severe,” others can be considered “mild.” The combination of alleles determines the type of Krabbe disease a person will have. To identify patients earlier, newborn screening (NBS) has been implemented in several states. Low GALC activity in this screening test may indicate a diagnosis of Krabbe disease. Second tier testing as well as neuro-diagnostic studies may be required to identify those individuals needing immediate treatment. Treatment of pre-symptomatic or mildly symptomatic patients at this time is limited to hematopoietic stem cell transplantation. Treatment studies using the mouse and dog models have shown that combining bone marrow transplantation with intra-venous gene therapy provides the best outcomes in terms of survival, behavior, and preservation of normal myelination in the central and peripheral nervous systems. With earlier diagnosis of patients through newborn screening and advances in treatment, it is hoped that more patients will have a much better quality of life.

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Bi-allelic variants in MTMR5/SBF1 cause Charcot-Marie-Tooth type 4B3 featuring mitochondrial dysfunction

BMC Medical Genomics ◽

10.1186/s12920-021-01001-1 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Beatrice Berti ◽

Giovanna Longo ◽

Francesco Mari ◽

Stefano Doccini ◽

Ilaria Piccolo ◽

...

Keyword(s):

Intellectual Disability ◽

Mitochondrial Dysfunction ◽

Early Onset ◽

Integrated Approach ◽

Compound Heterozygous ◽

Charcot Marie Tooth ◽

Charcot Marie Tooth Disease ◽

Pathogenic Variants ◽

First Case ◽

Spine Mri

Abstract Background Charcot-Marie-Tooth disease (CMT) type 4B3 (CMT4B3) is a rare form of genetic neuropathy associated with variants in the MTMR5/SBF1 gene. MTMR5/SBF1 is a pseudophosphatase predicted to regulate endo-lysosomal trafficking in tandem with other MTMRs. Although almost ubiquitously expressed, pathogenic variants primarily impact on the peripheral nervous system, corroborating the involvement of MTMR5/SBF1 and its molecular partners in Schwann cells-mediated myelinization. Case presentation We report a case of severe CMT4B3 characterized by early-onset motor and axonal polyneuropathy in an Italian child in absence of any evidence of brain and spine MRI abnormalities or intellectual disability and with a biochemical profile suggestive of mitochondrial disease. Using an integrated approach combining both NGS gene panels and WES analysis, we identified two novel compound heterozygous missense variants in MTMR5/SBF1 gene, p.R763H (c.2291G > A) and p.G1064E (c.3194G > A). Studies in muscle identified partial defects of oxidative metabolism. Conclusion We describe the first case of an early onset severe polyneuropathy with motor and axonal involvement, due to recessive variants in the MTMR5/SBF1 gene, with no evidence of brain and spine MRI abnormalities, intellectual disability, no clinical and neurophysiological evidences of distal sensory impairment, and rapid neuromuscular deterioration. This report suggests that MTMR5/SBF1 should be considered in cases of infantile-onset CMT with secondary mitochondrial dysfunction.

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MO1027EFFICACY OF CALCINEURIN INHIBITORS IN CHILDREN WITH MONOGENIC STEROID-RESISTANT NEPHROTIC SYNDROME

Nephrology Dialysis Transplantation ◽

10.1093/ndt/gfab108.0024 ◽

2021 ◽

Vol 36 (Supplement_1) ◽

Author(s):

Larisa Prikhodina ◽

Svetlana Papizh ◽

Inna Povolotskaya

Keyword(s):

Nephrotic Syndrome ◽

Calcineurin Inhibitors ◽

Compound Heterozygous ◽

Target Level ◽

Steroid Resistant ◽

Steroid Resistant Nephrotic Syndrome ◽

Pathogenic Variants ◽

Nail Patella Syndrome

Abstract Background and Aims Monogenic causes of steroid-resistant nephrotic syndrome (SRNS) have been reported for up to one-third of children depending on age of the disease onset. Immunosuppressive treatment of genetic SRNS with calcineurin inhibitors (CNIs) is still controversial. The aim of the study was to investigate the efficacy of CNIs with focus on inducing remission and long-term kidney function in children with monogenic SRNS. Method Retrospective analysis of efficacy CNIs in five children (2M/3F) with monogenic SRNS was performed. Kidney biopsy prior CNIs revealed FSGS (n=4) and MCD (n=1). The initial cyclosporine (CsA) dose was 5 mg/kg/24h to keep a target level of 80-150 ng/ml and tacrolimus (TAC) - 0.1 mg/kg/24h to achieve a target level of 5-10 ng/ml. CsA took all 5 patients with subsequent switching to TAC in 2 children due to cosmetic side effects. The median follow-up period was 165.0 (IQR: 59.0; 185.5) months. Next generation sequencing (NGS) was used for identification of pathogenic variants in all patients. Results The median age at onset of monogenic SRNS was 33.0 (IQR: 16.5; 63.0) months. 2/5 (40%) patients presented with acute SRNS, 1/5 (20%) child with infantile NS, 1/5 (20%) - with isolated nephrotic range proteinuria with hypoalbuminemia and 1/5 (20%) - with NS and extrarenal features of Nail-Patella syndrome. NGS identified previously described pathogenic variants in all 5 children, including NPHS2 homozygous c.28dup (p.Glu87Ter) (n=1), NPHS2 compound heterozygous c.868G>A (p.Val290Met) in combination with c.686G>A (p.Arg229Gln) (n=1), LMX1B heterozygous c.788T>G (p.Val263Gly) (n=1), LMX1B heterozygous c.737G>A (p.Arg246Gln) (n=1), and COL4A3 heterozygous c.2962G>A (p.Gly988Arg) variant (n=1). The median time from diagnosis to initiation of CNIs treatment was 72.0 (IQR: 33.0; 93.0) months. CNIs induced complete remission in 2/5 (40%) patients, presented with acute SRNS, including one girl with MCD due to NPHS2 compound heterozygous variants with mutation-dependent pathogenicity of one (p.R229Q) of them and one boy with FSGS due to COL4A3 heterozygous variant (n=1). Partial remission was induced by CNIs in 2/5 (40%) girls with FSGS due to LMX1B heterozygous variants with isolated SRNS (n=1) and Nail-Patella syndrome (n=1). The median duration of CNIs treatment to obtain complete or partial remission was 13.5 (IQR: 6.8; 15.8) months. Acute CNIs-associated nephrotoxicity had 2 patients with LMX1B variants. At the last follow up full and partial responders to CNIs treatment aged of 16.5 (IQR: 11.8; 17.5) years had CKD-1 (n=3) and CKD-2 (n=1). 1/5 (20%) boy with NPHS2-associated infantile NS was CNI resistant and developed CKD-5 at the age of 6.5 years with subsequent living related kidney transplantation. Conclusion We found that 4/5 (80%) children with monogenic SRNS demonstrated partial or full response to CNIs treatment with stable long-term kidney function. We assume that CNIs might improve podocyte function by stabilization of their cytoskeleton disrupted in patients with monogenic SRNS.

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Novel Sodium/Iodide Symporter Compound Heterozygous Pathogenic Variants Causing Dyshormonogenic Congenital Hypothyroidism

Thyroid ◽

10.1089/thy.2019.0046 ◽

2019 ◽

Vol 29 (7) ◽

pp. 1023-1026 ◽

Cited By ~ 4

Author(s):

Mariano Martín ◽

Carlos Eduardo Bernal Barquero ◽

Romina Celeste Geysels ◽

Patricia Papendieck ◽

Victoria Peyret ◽

...

Keyword(s):

Congenital Hypothyroidism ◽

Sodium Iodide ◽

Compound Heterozygous ◽

Sodium Iodide Symporter ◽

Pathogenic Variants

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Can early treatment of twitcher mice with high dose AAVrh10-GALC eliminate the need for BMT?

Bioimpacts ◽

10.34172/bi.2021.21 ◽

2021 ◽

Vol 11 (2) ◽

pp. 135-146

Author(s):

Mohammad A Rafi ◽

Paola Luzi ◽

David A Wenger

Keyword(s):

Gene Therapy ◽

Stem Cell ◽

Stem Cell Transplantation ◽

Cell Transplantation ◽

Viral Vector ◽

Krabbe Disease ◽

High Dose ◽

Restriction Enzyme Digestion ◽

Hematopoietic Stem ◽

Galc Gene

Introduction: Krabbe disease (KD) is an autosomal recessive disorder caused by mutations in the galactocerebrosidase (GALC) gene resulting in neuro-inflammation and defective myelination in the central and peripheral nervous systems. Most infantile patients present with clinical features before six months of age and die before two years of age. The only treatment available for pre-symptomatic or mildly affected individuals is hematopoietic stem cell transplantation (HSCT). In the animal models, combining bone marrow transplantation (BMT) with gene therapy has shown the best results in disease outcome. In this study, we examine the outcome of gene therapy alone. Methods: Twitcher (twi) mice used in the study, have a W339X mutation in the GALC gene. Genotype identification of the mice was performed shortly after birth or post-natal day 1 (PND1), using polymerase chain reaction on the toe clips followed by restriction enzyme digestion and electrophoresis. Eight or nine-day-old affected mice were used for gene therapy treatment alone or combined with BMT. While iv injection of 4 × 1013 gc/kg of body weight of viral vector was used originally, different viral titers were also used without BMT to evaluate their outcomes. Results: When the standard viral dose was increased four- and ten-fold (4X and 10X) without BMT, the lifespans were increased significantly. Without BMT the affected mice were fertile, had the same weight and appearance as wild type mice and had normal strength and gait. The brains showed no staining for CD68, a marker for activated microglia/macrophages, and less astrogliosis than untreated twi mice. Conclusion: Our results demonstrate that, it may be possible to treat human KD patients with high dose AAVrh10 without blood stem cell transplantation which would eliminate the side effects of HSCT.

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Pitt Hopkins-Like Syndrome 1 with Novel CNTNAP2 Mutation in Siblings

Child Neurology Open ◽

10.1177/2329048x211055330 ◽

2021 ◽

Vol 8 ◽

pp. 2329048X2110553

Author(s):

Rea Mittal ◽

Ashutosh Kumar ◽

Roger Ladda ◽

Gayatra Mainali ◽

Ermal Aliu

Keyword(s):

Developmental Delay ◽

Focal Epilepsy ◽

Autism Spectrum ◽

Compound Heterozygous ◽

Sequencing Analysis ◽

Gait Abnormality ◽

Pathogenic Variants ◽

Obstructive Sleep ◽

Management Guidance ◽

Intragenic Deletions

Pitt Hopkins-like syndrome 1 (PTHLS1, OMIM # 610042) is an ultra-rare autosomal recessive condition with a prevalence of <1/1,000,000. Intragenic deletions of CNTNAP2 has been implicated in PTHLS1, however to our knowledge a compound heterozygous deletion of exon 4 and a c.1977_1989del13; p.V660Ffsx9 frameshift variant have not been published previously. In this case report, the proband is a seven year old female with PTHLS1, developmental delay, autism spectrum disorder, focal epilepsy, hypotonia, refractory errors, strabismus, and obstructive sleep apnea. Whole exome sequencing analysis revealed biallelic pathogenic variants of the CNTNAP2 gene. Proband has a three year old sister who has who has a similar phenotype including, developmental delay, epilepsy, gait abnormality, refractory errors, strabismus. Family variants were tested and she shared the same CNTNAP2 variants as her sister. The sisters described highlight two novel variants leading to PTHLS1. Genetic workup is essential in identification and management guidance in these populations.

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Novel compound heterozygous EYS variants may be associated with arRP in a large Chinese pedigree

Bioscience Reports ◽

10.1042/bsr20193443 ◽

2020 ◽

Vol 40 (6) ◽

Cited By ~ 1

Author(s):

Chunli Wei ◽

Ting Xiao ◽

Jingliang Cheng ◽

Jiewen Fu ◽

Qi Zhou ◽

...

Keyword(s):

Novel Mutation ◽

Gene Mutations ◽

Chinese Family ◽

Compound Heterozygous ◽

Missense Mutations ◽

The Novel ◽

Pathogenic Variants ◽

Pathogenic Genes ◽

Compound Heterozygous Variants ◽

Normal Controls

Abstract As a genetically heterogeneous ocular dystrophy, gene mutations with autosomal recessive retinitis pigmentosa (arRP) in patients have not been well described. We aimed to detect the disease-causing genes and variants in a Chinese arRP family. In the present study, a large Chinese pedigree consisting of 31 members including a proband and another two patients was recruited; clinical examinations were conducted; next-generation sequencing using a gene panel was used for identifying pathogenic genes, and Sanger sequencing was performed for verification of mutations. Novel compound heterozygous variants c.G2504A (p.C835Y) and c.G6557A (p.G2186E) for the EYS gene were identified, which co-segregated with the clinical RP phenotypes. Sequencing of 100 ethnically matched normal controls didn’t found these mutations in EYS. Therefore, our study identified pathogenic variants in EYS that may cause arRP in this Chinese family. This is the first study to reveal the novel mutation in the EYS gene (c.G2504A, p.C835Y), extending its mutation spectrum. Thus, the EYS c.G2504A (p.C835Y) and c.G6557A (p.G2186E) variants may be the disease-causing missense mutations for RP in this large arRP family. These findings should be helpful for molecular diagnosis, genetic counseling and clinical management of arRP disease.

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