Whole Exome Sequencing detects PYGM variants in two adults with McArdle disease

McArdle disease is a progressive and debilitating glycogen storage disease with typical onset in late childhood. Here we describe a former competitive athlete with early adult onset McArdle disease and a septuagenarian with a history of exercise-intolerance since adolescence who was evaluated for proximal muscle weakness. Exome sequencing identified bi-allelic variants in PYGM gene for both cases. The former athlete has the common, well-known pathogenic variant p.(Arg50Ter) in trans with a novel missense variant, p.(Asp694Glu). The second individual has a previously described homozygous missense variant, p.(Arg771Gln). Here, we describe the clinical course, enzyme-testing results using muscle tissue and molecular findings for the individuals, and add to the knowledge of the genotypic spectrum of this disorder.

Reprogramming the spleen into a functioning ‘liver’ in vivo

ObjectiveLiver regeneration remains one of the biggest clinical challenges. Here, we aim to transform the spleen into a liver-like organ via directly reprogramming the splenic fibroblasts into hepatocytes in vivo.DesignIn the mouse spleen, the number of fibroblasts was through silica particles (SiO2) stimulation, the expanded fibroblasts were converted to hepatocytes (iHeps) by lentiviral transfection of three key transcriptional factors (Foxa3, Gata4 and Hnf1a), and the iHeps were further expanded with tumour necrosis factor-α (TNF-α) and lentivirus-mediated expression of epidermal growth factor (EGF) and hepatocyte growth factor (HGF).ResultsSiO2 stimulation tripled the number of activated fibroblasts. Foxa3, Gata4 and Hnf1a converted SiO2-remodelled spleen fibroblasts into 2×106 functional iHeps in one spleen. TNF-α protein and lentivirus-mediated expression of EGF and HGF further enabled the total hepatocytes to expand to 8×106 per spleen. iHeps possessed hepatic functions—such as glycogen storage, lipid accumulation and drug metabolism—and performed fundamental liver functions to improve the survival rate of mice with 90% hepatectomy.ConclusionDirect conversion of the spleen into a liver-like organ, without cell or tissue transplantation, establishes fundamental hepatic functions in mice, suggesting its potential value for the treatment of end-stage liver diseases.

Clinical, pathological and molecular spectrum of patients with glycogen storage diseases in Pakistan

Objectives Evaluation of clinical, biochemical and molecular analysis of Pakistani patients with hepatic GSDs. Methods Medical charts, biochemical, histopathological and molecular results of patients with hepatic GSD were reviewed. Results Out of 55 GSD patients, 41 (74.5%) were males and 14 (25.5%) were females with consanguinity in 50 (91%) patients. The median age of initial symptoms, clinic diagnosis and molecular diagnosis were 450 (IQR: 270–960), 1,095 (IQR: 510–1,825) and 1717 (IQR: 796–3,011) days, respectively. Molecular analysis and enzyme activity was available for 33 (60%) and two patients, respectively. GSD III (n=9) was most prevalent followed by GSD Ib (n=7), GSD IXc (n=6), GSD VI (n=4), GSD Ia (n=3), GSD XI (n=3), GSD IXb (n=2) and GSD IXa (n=1). In patients (n=33) who underwent molecular analysis; 19 different variants in eight genes associated with GSD were identified. We also report five novel variants, two in SLC37A4, one in AGL and two in PYGL contributing to the diagnosis of GSD Ib, GSD III and GSD VI, respectively. Conclusions Fifty-five patients of GSDs in 26 families from a single care provider indicate a relatively high frequency of GSD in Pakistan, with multiple unrelated families harboring identical disease-causing variants, on molecular analysis, including two known pathogenic variants in SLC37A4 and PHKG2, and a novel variant in AGL.

Exosomal MicroRNAs as Potential Biomarkers of Hepatic Injury and Kidney Disease in Glycogen Storage Disease Type Ia Patients

Glycogen storage disease type Ia (GSDIa) is an inherited metabolic disorder caused by mutations in the enzyme glucose-6-phosphatase-α (G6Pase-α). Affected individuals develop renal and liver complications, including the development of hepatocellular adenoma/carcinoma and kidney failure. The purpose of this study was to identify potential biomarkers of the evolution of the disease in GSDIa patients. To this end, we analyzed the expression of exosomal microRNAs (Exo-miRs) in the plasma exosomes of 45 patients aged 6 to 63 years. Plasma from age-matched normal individuals were used as controls. We found that the altered expression of several Exo-miRs correlates with the pathologic state of the patients and might help to monitor the progression of the disease and the development of late GSDIa-associated complications.

Evaluation of Glycogen Storage Patients: Report of Twelve Novel Variants and New Clinical Findings in a Turkish Population

Glycogen storage diseases (GSDs) are clinically and genetically heterogeneous disorders that disturb glycogen synthesis or utilization. Although it is one of the oldest inherited metabolic disorders, new genetic methods and long-time patient follow-ups provide us with unique insight into the genotype–phenotype correlations. The aim of this study was to share the phenotypic features and molecular diagnostic results that include new pathogenic variants in our GSD cases. Twenty-six GSD patients were evaluated retrospectively. Demographic data, initial laboratory and imaging features, and current findings of the patients were recorded. Molecular analysis results were classified as novel or previously defined variants. Novel variants were analyzed with pathogenicity prediction tools according to American College of Medical Genetics and Genomics (ACGM) criteria. Twelve novel and rare variants in six different genes were associated with the disease. Hearing impairment in two patients with GSD I, early peripheral neuropathy after liver transplantation in one patient with GSD IV, epilepsy and neuromotor retardation in three patients with GSD IXA were determined. We characterized a heterogeneous group of all diagnosed GSDs over a 5-year period in our institution, and identified novel variants and new clinical findings. It is still difficult to establish a genotype–phenotype correlation in GSDs.

N6-methyladenosine modification governs liver glycogenesis by stabilizing the glycogen synthase 2 mRNA

Hepatic glycogen is the main source of blood glucose and controls the intervals between meals in mammals. Hepatic glycogen storage in mammalian pups is insufficient compared to their adult counterparts; however, the detailed molecular mechanism is poorly understood. Here, we showed that, similar to glycogen storage pattern, N6-methyladenosine (m6A) modification in mRNAs gradually increases during the growth of mice in liver. Strikingly, in the liver-specific Mettl3 knockout mice, loss of m6A modification disrupts liver glycogen storage. On the mechanism, we screened and identified that glycogen synthase 2 (Gys2) plays a critical role in m6A-mediated regulation of liver glycogen storage. Furthermore, IGF2BP2, as a “reader” of m6A, stabilizes the mRNA of Gys2. More importantly, reconstitution of GYS2 rescues liver glycogenesis in Mettl3-cKO mice. Collectively, a METTL3-IGF2BP2-GYS2 axis, in which METTL3 and IGF2BP2 regulate glycogenesis as “writer” and “reader” respectively, plays a critical role on maintenance of liver glycogenesis in mammals.