Neurofibromatosis type 1 (NF1) with an unusually severe phenotype due to digeny for NF1 and ryanodine receptor 1 associated myopathy

We describe a 5-year-old girl with marked hypotonia, poor feeding and reduced facial expression since birth. Congenital myopathy was suspected; muscle biopsy showed unspecific type 1 fibre predominance. The possibility of a ryanodine receptor 1 gene (RYR1)-associated myopathy was considered, but not further investigated. At the age of 2years, she presented with exophthalmos. Brain MRI revealed optic pathway glioma. On clinical examination, she had six café-au-lait spots, thus fulfilling the diagnostic criteria for neurofibromatosis type 1 (NF1). The hypotonia was then attributed to NF1. At the age of 3years, she developed scoliosis and had an unusually severe motor delay for NF1, as she was not able to walk independently. Dual pathology was suspected, and muscle MRI showed the typical pattern for RYR1-related myopathy. This was genetically confirmed with the discovery of two heterozygous mutations. Conclusion: NF1 is one of the most frequent genetic diseases in children. RYR1-related myopathy is one of the most frequent causes of congenital myopathy. The combination of these two pathologies has not yet been described. In cases of unusual presentations or clinical course, the possibility of genetic "double trouble” should be considered

Loss of NOTCH2 Positively Predicts Survival in Subgroups of Human Glial Brain Tumors

The structural complexity of chromosome 1p centromeric region has been an obstacle for fine mapping of tumor suppressor genes in this area. Loss of heterozygosity (LOH) on chromosome 1p is associated with the longer survival of oligodendroglioma (OD) patients. To test the clinical relevance of 1p loss in glioblastomas (GBM) patients and identifiy the underlying tumor suppressor locus, we constructed a somatic deletion map on chromosome 1p in 26 OG and 118 GBM. Deletion hotspots at 4 microsatellite markers located at 1p36.3, 1p36.1, 1p22 and 1p11 defined 10 distinct haplotypes that were related to patient survival. We found that loss of 1p centromeric marker D1S2696 within NOTCH2 intron 12 was associated with favorable prognosis in OD (P = 0.0007) as well as in GBM (P = 0.0175), while 19q loss, concomitant with 1p LOH in OD, had no influence on GBM survival (P = 0.918). Assessment of the intra-chromosomal ratio between NOTCH2 and its 1q21 pericentric duplication N2N (N2/N2N-test) allowed delineation of a consistent centromeric breakpoint in OD that also contained a minimally lost area in GBM. OD and GBM showed distinct deletion patterns that converged to the NOTCH2 gene in both glioma subtypes. Moreover, the N2/N2N-test disclosed homozygous deletions of NOTCH2 in primary OD. The N2/N2N test distinguished OD from GBM with a specificity of 100% and a sensitivity of 97%. Combined assessment of NOTCH2 genetic markers D1S2696 and N2/N2N predicted 24-month survival with an accuracy (0.925) that is equivalent to histological classification combined with the D1S2696 status (0.954) and higher than current genetic evaluation by 1p/19q LOH (0.762). Our data propose NOTCH2 as a powerful new molecular test to detect prognostically favorable gliomas

SARS-CoV-2 B.1.617.2 Delta variant replication and immune evasion

Abstract: The B.1.617.2 (Delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first identified in the state of Maharashtra in late 2020 and spread throughout India, outcompeting pre-existing lineages including B.1.617.1 (Kappa) and B.1.1.7 (Alpha)1. In vitro, B.1.617.2 is sixfold less sensitive to serum neutralizing antibodies from recovered individuals, and eightfold less sensitive to vaccine-elicited antibodies, compared with wild-type Wuhan-1 bearing D614G. Serum neutralizing titres against B.1.617.2 were lower in ChAdOx1 vaccinees than in BNT162b2 vaccinees. B.1.617.2 spike pseudotyped viruses exhibited compromised sensitivity to monoclonal antibodies to the receptor-binding domain and the amino-terminal domain. B.1.617.2 demonstrated higher replication efficiency than B.1.1.7 in both airway organoid and human airway epithelial systems, associated with B.1.617.2 spike being in a predominantly cleaved state compared with B.1.1.7 spike. The B.1.617.2 spike protein was able to mediate highly efficient syncytium formation that was less sensitive to inhibition by neutralizing antibody, compared with that of wild-type spike. We also observed that B.1.617.2 had higher replication and spike-mediated entry than B.1.617.1, potentially explaining the B.1.617.2 dominance. In an analysis of more than 130 SARS-CoV-2-infected health care workers across three centres in India during a period of mixed lineage circulation, we observed reduced ChAdOx1 vaccine effectiveness against B.1.617.2 relative to non-B.1.617.2, with the caveat of possible residual confounding. Compromised vaccine efficacy against the highly fit and immune-evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era

Prion pathogenesis is unaltered in the absence of SIRPα-mediated "don't-eat-me" signaling

Prion diseases are neurodegenerative conditions caused by misfolding of the prion protein, leading to conspicuous neuronal loss and intense microgliosis. Recent experimental evidence point towards a protective role of microglia against prion-induced neurodegeneration, possibly through elimination of prion-containing apoptotic bodies. The molecular mechanisms by which microglia recognize and eliminate apoptotic cells in the context of prion diseases are poorly defined. Here we investigated the possible involvement of signal regulatory protein α (SIRPα), a key modulator of host cell phagocytosis; SIRPα is encoded by the Sirpa gene that is genetically linked to the prion gene Prnp. We found that Sirpa transcripts are highly enriched in microglia cells within the brain. However, Sirpa mRNA levels were essentially unaltered during the course of experimental prion disease despite upregulation of other microglia-enriched transcripts. To study the involvement of SIRPα in prion pathogenesis in vivo, mice expressing a truncated SIRPα protein unable to inhibit phagocytosis were inoculated with rodent-adapted scrapie prions of the 22L strain. Homozygous and heterozygous Sirpa mutants and wild-type mice experienced similar incubation times after inoculation with either of two doses of 22L prions. Moreover, the extent of neuronal loss, microgliosis and abnormal prion protein accumulation was not significantly affected by Sirpa genotypes. Collectively, these data indicate that SIRPα-mediated phagocytosis is not a major determinant in prion disease pathogenesis. It will be important to search for additional candidates mediating prion phagocytosis, as this mechanism may represent an important target of antiprion therapies

Muscle magnetic resonance imaging of the lower limbs: Valuable diagnostic tool in the investigation of childhood neuromuscular disorders

Children presenting with neuromuscular symptoms are subject to exhaustive investigations. As it is noninvasive, muscle magnetic resonance imaging (MRI) is an important diagnostic tool in children, yet its impact has so far been mainly studied in small groups of genetically defined diseases, where specific MRI patterns are known. To assess the contribution of muscle MRI of the lower limbs in a diverse cohort of patients, we reviewed the diagnostic findings in 39 patients with a suspected neuromuscular disorder that underwent muscle MRI (28/39), biopsy (26/39), or both (18/39). MRI was performed without sedation in 26 of 28 patients at a mean age of 10 years (range, 1-27 years). In 10 of 28 cases (35%), MRI significantly contributed to the final diagnosis, and in 7 of 28 cases (25%), muscle MRI directly instructed genetic testing. These cases included Bethlem myopathy, laminopathy, calpainopathy, and RYR1-related myopathies. Muscle MRI serves as a valuable additional tool to guide diagnosis in suspected neuromuscular disorders in children, especially in cases with nonspecific biopsy findings