Molecular genetics of the POMT1-related muscular dystrophy-dystroglycanopathies

Identification of glycosyltransferase genes for diagnosis of T-cell mediated rejection and prediction of graft loss in kidney transplantation

BACKGROUND

Glycosylation is a complex and fundamental metabolic biosynthetic process orchestrated by multiple glycosyltransferases (GT) and glycosidases enzymes. Functions of GT have been extensively examined in multiple human diseases. Our study investigated the potential role of GT genes in T-cell mediated rejection (TCMR) and possible prediction of graft loss of kidney transplantation.

METHODS

We downloaded the microarray datasets and GT genes from the GEO and the HUGO Gene Nomenclature Committee (HGNC) databases, respectively. Differentially expressed GT genes (DE-GTGs) were obtained by differential expression and Venn analysis. A TCMR diagnostic model was developed based on the hub DE-GTGs using LASSO regression and XGboost machine learning algorithms. In addition, a predictive model for graft survival was constructed by univariate Cox and LASSO Cox regression analysis.

RESULTS

We have obtained 15 DE-GTGs. Both GO and KEGG analyses showed that the DE-GTGs were mainly involved in the glycoprotein biosynthetic process. The TCMR diagnostic model exhibited high diagnostic potential with generally highly correlated accuracies [aera under the curve (AUC) of 0.83]. The immune characteristics analysis revealed that higher levels of immune cell infiltration and immune responses were observed in the high-risk group than in the low-risk group. In particular, the Kaplan-Meier survival analysis revealed that renal grafts in the high-risk group have poor prognostic outcomes than the low-risk group. The predictive AUC values of 1-, 2- and 3-year graft survival were 0.76, 0.81, and 0.70, respectively.

CONCLUSION

Our results indicated that GT genes could be used for diagnosis of TCMR and prediction of graft loss in kidney transplantation. These results provide new perspectives and tools for diagnosing, treating and predicting kidney transplant-related diseases.

Broad spectrum of phenotype and genotype in Korean alpha dystroglycan related muscular dystrophy presenting to a tertiary pediatric neuromuscular center

α-Dystroglycanopathies are a clinically and genetically heterogeneous group of muscular dystrophies associated with the defective glycosylation of α-dystroglycan (α-DG). Eighteen genes associated with α-dystroglycanopathies have been identified, and the relative prevalence of genetic subtypes varies with ethnicity. Here, we investigated the clinical and genetic characteristics of α-DG-related muscular dystrophy in the Korean pediatric population. We analyzed the clinical characteristics and variant profiles of 42 patients with α-DG-related muscular dystrophies diagnosed by either reduced glycosylation of α-DG and/or genetic confirmation. Genotype-phenotype correlations were explored by a retrospective medical record review. The muscle-eye-brain disease/Fukuyama congenital muscular dystrophy was the most common phenotype (28/42, 66.7%). Homozygous or compound heterozygous variants were detected in 37 patients belonging to 34 unrelated families (37/42; 88.1%). Pathogenic variants were identified in FKTN (n = 24), POMGNT1 (n = 4), GMPPB (n = 4), FKRP (n = 2), POMT1 (n = 2), and ISPD (n = 1). Compound heterozygous retrotransposal insertions and deep-intronic variants in FKTN were the most common genotypes and were associated with severe phenotypes. This study suggests that α-DG-related muscular dystrophy has a wide range of genotypes and phenotypes according to ethnicity. A stratified genetic test according to ethnicity should be considered to diagnose α-DG-related muscular dystrophy.

Pediatric Brain Maturation and Migration Disorders

Neurodevelopmental disorders, including neuronal migration disorders, are best understood in the context of altered normal development. Neurons normally migrate from their site of origin to their (usually cortical) destination using a wide range of molecular and cellular signaling as a guide. In the case of abnormal migration neurons: (1) do not migrate and remain at their site of origin; (2) incompletely migrate and remain within the white matter; (3) migrate to the cortex but fail to organize correctly; or (4) over-migrate, beyond the cortex. In this review, we discuss normal brain development, along with the malformations that result from these different migration abnormalities.

CAR T-Cell Therapy for Relapsed/Refractory Diffuse Large B-Cell Lymphoma with Progressive Muscular Dystrophy: A Case Report

Muscular dystrophies are a heterogeneous group of genetically inherited degenerative disorders defined by dystrophic features on pathological assessment of muscle biopsy specimens. Muscular dystrophies and lymphoma are not common concomitant diseases. Chimeric antigen receptor (CAR) T-cell immunotherapy for lymphoma patients with inherited degenerative diseases, such as muscular dystrophies, has not been previously reported. We report a relapsed/refractory diffuse large B-cell lymphoma (DLBCL) patient with progressive muscular dystrophy (PMD) characterized by progressive muscle weakness that affected the limb, axial and facial muscles. He was identified to be a germline DYSF p.R204* homozygous mutation carrier. The patient received a murine monoclonal anti-CD19 and anti-CD22 CAR T-cell “cocktail” and suffered from a mild case of grade 1 cytokine release syndrome (CRS). One month after the CAR T-cell infusion, he achieved complete remission of his lymphoma without minimal residual disease (MRD), as assessed by radiography. One year after the infusion, the Deauville score was stable at 1. Currently, patient has been in remission for over three years after receiving anti-CD19 and anti-CD22 CAR T-cell therapy. This case provides evidence for the use of CAR T-cell therapy in lymphoma patients with inherited degenerative disorders. Achieving remission of the lymphoma and subsequent administration of γ-globulin as well as zoledronic acid reduced the muscular dystrophy symptoms.

Enhanced influenza A H1N1 T cell epitope recognition and cross-reactivity to protein-O-mannosyltransferase 1 in Pandemrix-associated narcolepsy type 1

Narcolepsy type 1 (NT1) is a chronic neurological disorder having a strong association with HLA-DQB1*0602, thereby suggesting an immunological origin. Increased risk of NT1 has been reported among children or adolescents vaccinated with AS03 adjuvant-supplemented pandemic H1N1 influenza A vaccine, Pandemrix. Here we show that pediatric Pandemrix-associated NT1 patients have enhanced T-cell immunity against the viral epitopes, neuraminidase 175-189 (NA175-189) and nucleoprotein 214-228 (NP214-228), but also respond to a NA175-189-mimic, brain self-epitope, protein-O-mannosyltransferase 1 (POMT1675-689). A pathogenic role of influenza virus-specific T-cells and T-cell cross-reactivity in NT1 are supported by the up-regulation of IFN-γ, perforin 1 and granzyme B, and by the converging selection of T-cell receptor TRAV10/TRAJ17 and TRAV10/TRAJ24 clonotypes, in response to stimulation either with peptide NA175-189 or POMT1675-689. Moreover, anti-POMT1 serum autoantibodies are increased in Pandemrix-vaccinated children or adolescents. These results thus identify POMT1 as a potential autoantigen recognized by T- and B-cells in NT1.

Genetic variations and clinical spectrum of dystroglycanopathy in a large cohort of Chinese patients

Dystroglycanopathy is a group of muscular dystrophies with deficient glycosylation of alpha-dystroglycan (α-DG). We recruited patients from 36 tertiary academic hospitals in China. In total, 143 patients with genetically diagnosed dystroglycanopathy were enrolled. Of these, limb girdle muscular dystrophy was the most common initial diagnosis (83 patients) and Walker-Warburg syndrome was the least common (1 patient). In 143 patients, mutations in FKRP gene were the most prevalent (62 patients), followed by POMT2, POMT1 (16), POMGNT1, ISPD (14), FKTN, GMPPB, B3GALNT2, DPM3, and DAG1. Several frequent mutations were identified in FKRP, POMT1, POMGNT1, ISPD, and FKTN genes. Many of these were founder mutations. Patients with FKRP mutations tended to have milder phenotypes, while those with mutations in POMGNT1 genes had more severe phenotypes. Mental retardation was a clinical feature associated with mutations of POMT1 gene. Detailed clinical data of 83 patients followed up in Peking University First Hospital were further analyzed. Our clinical and genetic analysis of a large cohort of Chinese patients with dystroglycanopathy expanded the genotype variation and clinical spectrum of congenital muscular dystrophies.

Congenital Disorders of Glycosylation: What Clinicians Need to Know?

Congenital disorders of glycosylation (CDG) are a group of clinically heterogeneous disorders characterized by defects in the synthesis of glycans and their attachment to proteins and lipids. This manuscript aims to provide a classification of the clinical presentation, diagnostic methods, and treatment of CDG based on the literature review and our own experience (referral center in Poland). A diagnostic algorithm for CDG was also proposed. Isoelectric focusing (IEF) of serum transferrin (Tf) is still the method of choice for diagnosing N-glycosylation disorders associated with sialic acid deficiency. Nowadays, high-performance liquid chromatography, capillary zone electrophoresis, and mass spectrometry techniques are used, although they are not routinely available. Since next-generation sequencing became more widely available, an improvement in diagnostics has been observed, with more patients and novel CDG subtypes being reported. Early and accurate diagnosis of CDG is crucial for timely implementation of appropriate therapies and improving clinical outcomes. However, causative treatment is available only for few CDG types.

Structure of the eukaryotic protein O-mannosyltransferase Pmt1-Pmt2 complex

In eukaryotes, a nascent peptide entering the endoplasmic reticulum (ER) is scanned by two Sec61-translocon-associated large membrane machines for protein N-glycosylation and protein O-mannosylation, respectively. While the structure of the eight-protein oligosaccharyltransferase complex has been determined recently, the structures of mannosyltransferases of the PMT family, which are an integral part of ER protein homeostasis, are still unknown. Here we report cryo-EM structures of the S. cerevisiae Pmt1–Pmt2 complex bound to a donor and an acceptor peptide at 3.2-Å resolution, showing that each subunit contains 11 transmembrane helices and a lumenal β-trefoil fold termed the MIR domain. The structures reveal the substrate recognition model and confirm an inverting mannosyl-transferring reaction mechanism by the enzyme complex. Furthermore, we found that the transmembrane domains of Pmt1 and Pmt2 share a structural fold with the catalytic subunits of oligosaccharyltransferases, confirming a previously proposed evolutionary relationship between protein O-mannosylation and protein N-glycosylation.