Minimally disseminated disease and outcome in overt orbital retinoblastoma

In this retrospective study of patients with overt orbital retinoblastoma, we evaluated minimally disseminated disease (MDD) in bone marrow and cerebrospinal fluid (CSF) using CRX and/or GD2 synthase as markers. Ten patients were evaluated-five (50%) at diagnosis and five upon relapse. MDD was detected in four cases (one in the bone marrow, two in the CSF, and in one case in both sites). All patients received chemotherapy and four received orbital radiotherapy. Seven patients relapsed or progressed and all of them died. Three patients remain in complete remission. There was no apparent correlation between MDD and the outcome.

Mitochondrial stress triggers a pro-survival response through epigenetic modifications of nuclear DNA

Mitochondrial dysfunction represents an important cellular stressor and when intense and persistent cells must unleash an adaptive response to prevent their extinction. Furthermore, mitochondria can induce nuclear transcriptional changes and DNA methylation can modulate cellular responses to stress. We hypothesized that mitochondrial dysfunction could trigger an epigenetically mediated adaptive response through a distinct DNA methylation patterning. We studied cellular stress responses (i.e., apoptosis and autophagy) in mitochondrial dysfunction models. In addition, we explored nuclear DNA methylation in response to this stressor and its relevance in cell survival. Experiments in cultured human myoblasts revealed that intense mitochondrial dysfunction triggered a methylation-dependent pro-survival response. Assays done on mitochondrial disease patient tissues showed increased autophagy and enhanced DNA methylation of tumor suppressor genes and pathways involved in cell survival regulation. In conclusion, mitochondrial dysfunction leads to a "pro-survival" adaptive state that seems to be triggered by the differential methylation of nuclear genes.

'Dusty core disease' (DuCD): expanding morphological spectrum of RYR1 recessive myopathies

Several morphological phenotypes have been associated to RYR1-recessive myopathies. We recharacterized the RYR1-recessive morphological spectrum by a large monocentric study performed on 54 muscle biopsies from a large cohort of 48 genetically confirmed patients, using histoenzymology, immunohistochemistry, and ultrastructural studies. We also analysed the level of RyR1 expression in patients’ muscle biopsies. We defined “dusty cores” the irregular areas of myofibrillar disorganisation characterised by a reddish-purple granular material deposition with uneven oxidative stain and devoid of ATPase activity, which represent the characteristic lesion in muscle biopsy in 54% of patients. We named Dusty Core Disease (DuCD) the corresponding entity of congenital myopathy. Dusty cores had peculiar histological and ultrastructural characteristics compared to the other core diseases. DuCD muscle biopsies also showed nuclear centralization and type1 fibre predominance. Dusty cores were not observed in other core myopathies and centronuclear myopathies. The other morphological groups in our cohort of patients were: Central Core (CCD: 21%), Core-Rod (C&R:15%) and Type1 predominance “plus” (T1P+:10%). DuCD group was associated to an earlier disease onset, a more severe clinical phenotype and a lowest level of RyR1 expression in muscle, compared to the other groups. Variants located in the bridge solenoid and the pore domains were more frequent in DuCD patients. In conclusion, DuCD is the most frequent histopathological presentation of RYR1-recessive myopathies. Dusty cores represent the unifying morphological lesion among the DuCD pathology spectrum and are the morphological hallmark for the recessive form of disease.

Sarcomeric disorganization and nemaline bodies in muscle biopsies of patients with EXOSC3-related type 1 pontocerebellar hypoplasia

INTRODUCTION

Mutations in the EXOSC3 gene are responsible for type 1 pontocerebellar hypoplasia, an autosomal recessive congenital disorder characterized by cerebellar atrophy, developmental delay, and anterior horn motor neuron degeneration. Muscle biopsies of these patients often show characteristics resembling classic spinal muscle atrophy, but to date, no distinct features have been identified.

METHODS

Clinical data and muscle biopsy findings of 3 unrelated patients with EXOSC3 mutations are described.

RESULTS

All patients presented as a severe congenital cognitive and neuromuscular phenotype with short survival, harboring the same point mutation (c.92G>C; p.Gly31Ala). Muscle biopsies consistently showed variable degrees of sarcomeric disorganization with myofibrillar remnants, Z-line thickening, and small nemaline bodies.

CONCLUSIONS

In this uniform genetic cohort of patients with EXOSC3 mutations, sarcomeric disruption and rod structures were prominent features of muscle biopsies. In the context of neonatal hypotonia, ultrastructural studies might provide early clues for the diagnosis of EXOSC3-related pontocerebellar hypoplasia. Muscle Nerve 59:137-141, 2019.

Aberrant O-glycosylation modulates aggressiveness in neuroblastoma

Neuroblastoma (NB) is the most common pediatric malignancy diagnosed before the first birthday in which MYCN oncogene amplification is associated with poor prognosis. Although aberrant glycosylation is an important actor in cell biology, little is known about its role in pediatric cancers such as NB. In this work we characterized the glycophenotype and the enzyme expression involved in glycans biosynthesis in five established human NB cell lines and in patient-derived primary tumors with different MYCN status. Our results show a high expression of Lewis glycan family both in MYCN-amplified cell lines and patient samples. Additionally, we report that MYCN-amplified cells overexpressed Core 2-initiating glycosyltransferase C2GNT1 in association with specific ST3Gals and FUTs, and showed increased binding to E- and P- selectins. Silencing of C2GNT1 expression in NB cells diminished expression of Lewis glycans, decreased the E- and P-selectin binding, and reduced cell adhesion, migration and proliferation in vitro. Treatment of MYCN-non-amplified cells with Trichostatin A (TSA), an histone deacetylase inhibitor, increased the expression of Lewis glycans and the enzymes involved in their biosynthesis. Our results demonstrate that MYCN-amplified NB cells overexpress Lewis family glycans, which belong to the Core 2 O-glycans group. Their expression plays a key role in the malignant behaviour of the NB cells and it is modulated by epigenetic mechanisms.

The Netrin-4/Laminin γ1/Neogenin-1 complex mediates migration in SK-N-SH neuroblastoma cells

Neuroblastoma (NB) is the most common pediatric extracranial solid tumor. It arises during development of the sympathetic nervous system. Netrin-4 (NTN4), a laminin-related protein, has been proposed as a key factor to target NB metastasis, although there is controversy about its function. Here, we show that NTN4 is broadly expressed in tumor, stroma and blood vessels of NB patient samples. Furthermore, NTN4 was shown to act as a cell adhesion molecule required for the migration induced by Neogenin-1 (NEO1) in SK-N-SH neuroblastoma cells. Therefore, we propose that NTN4, by forming a ternary complex with Laminin γ1 (LMγ1) and NEO1, acts as an essential extracellular matrix component, which induces the migration of SK-N-SH cells.

[Argentine consensus on late-onset Pompe's disease]

Pompe's disease (PD) is an infrequent metabolic autosomic recessive disorder produced by the lack or deficiency of the acid alpha-glucosidase lysosomal enzyme in tissues of involved individuals. Delayed-onset PD is considered whenever symptoms onset start after one year of age. We present an update of the recommendations for the management of delayed-onset PD, taking as reference the guidelines from the Argentine Consensus for diagnosis, treatment and follow-up of PD published in 2013. The present consensus gathered several experts in PD in the areas of internal medicine, laboratory diagnosis, neuropathology, pulmonology, nutrition, neurology, metabolic and neuromuscular disorders as well as rehabilitation to perform an update of the literature of delayed-onset PD, with special attention on relevant information published within the last 4 years. The entire working group approved the final version of the consensus. Each participant provided a declaration of conflict of interest. As a result, it is an update of the previous Argentine PD Consensus with focus on the delayed-onset presentation of the disease. Being such infrequent disorder, available data were rather limited and thus, the recommendations represent expert opinions.

[Cerebral hydatid disease: report of six pediatric cases]

Hydatid disease is a parasitic infection whose etiologic agent is Echinococcus granulosus. Human is an accidental intermediate host and the most common site is the liver. The brain involvement is unusual and up to 75% of cases are described in the pediatric population. We present six children with cerebral hydatid disease admitted to the Pediatric Hospital J.P. Garrahan. All had neurological involvement on admission. The images showed single cystic lesion in the brain. They did not present involvement in other organs. Serology was negative in all cases. Medical and surgical treatment in all cases. The clinical outcome was favorable without sequelae in five of them and one had a residual paresis right faciobrachiocrural. This infection should be considered in the differential diagnosis of cystic tumor lesions of the central nervous system.

Common and variable clinical, histological, and imaging findings of recessive RYR1-related centronuclear myopathy patients

Mutations in RYR1 give rise to diverse skeletal muscle phenotypes, ranging from classical central core disease to susceptibility to malignant hyperthermia. Next-generation sequencing has recently shown that RYR1 is implicated in a wide variety of additional myopathies, including centronuclear myopathy. In this work, we established an international cohort of 21 patients from 18 families with autosomal recessive RYR1-related centronuclear myopathy, to better define the clinical, imaging, and histological spectrum of this disorder. Early onset of symptoms with hypotonia, motor developmental delay, proximal muscle weakness, and a stable course were common clinical features in the cohort. Ptosis and/or ophthalmoparesis, facial weakness, thoracic deformities, and spinal involvement were also frequent but variable. A common imaging pattern consisted of selective involvement of the vastus lateralis, adductor magnus, and biceps brachii in comparison to adjacent muscles. In addition to a variable prominence of central nuclei, muscle biopsy from 20 patients showed type 1 fiber predominance and a wide range of intermyofibrillary architecture abnormalities. All families harbored compound heterozygous mutations, most commonly a truncating mutation combined with a missense mutation. This work expands the phenotypic characterization of patients with recessive RYR1-related centronuclear myopathy by highlighting common and variable clinical, histological, and imaging findings in these patients.

Identification of ZCCHC8 as fusion partner of ROS1 in a case of congenital glioblastoma multiforme with a t(6;12)(q21;q24.3)

Congenital gliobastoma multiforme (GBM) is rare and little is known about the molecular defects underlying the initiation and progression of this tumor type. We present a case of congenital GBM analyzed by conventional cytogenetics, fluorescence in situ hybridization, array comparative genomic hybridization and next generation sequencing. On cytogenetic analysis we detected a reciprocal translocation t(6;12)(q21;q24.3). By sequencing, the translocation was shown to form a fusion between the 5' region of ZCCHC8 and the 3' region of ROS1. RT-PCR analyses confirmed the existence of an in-frame fusion transcript with ZCCHC8 exons 1-3 joined to ROS1 exons 36-43. In addition to the ZCCHC8-ROS1 fusion, we detected a deletion in the short arm of chromosome 9, including homozygous loss of the CDKN2A/2B locus in 9p21.3 and heterozygous deletion of the HAUS6 gene in 9p22.1. The latter encodes a protein involved in faithful chromosome segregation by regulating microtubule nucleation and its deletion might be associated with the marked subclonal changes of ploidy observed in the tumor. This report adds the ZCCHC8-ROS1 fusion as oncogenic driver in GBM and supports the role of ROS1 activation in the pathogenesis of a subset of GBM. © 2016 Wiley Periodicals, Inc.

Mitochondrial DNA deletions detected by Multiplex Ligation-dependent Probe Amplification

The genetic diagnosis algorithm for mitochondrial (mt) diseases starts looking for deletions and common mutations in mtDNA. MtDNA's special features, such as large and variable genome copies, heteroplasmy, polymorphisms, and its duplication in the nuclear genome as pseudogenes (NUMTs), make it vulnerable to diagnostic misleading interpretations. Multiplex Ligation-dependent Probe Amplification (MLPA) is used to detect copy number variations in nuclear genes and its application on mtDNA has not been widely spread. We report three Kearns Sayre Syndrome patients and one Chronic Progressive External Ophthalmoplegia adult, whose diagnostic mtDNA deletions were detected by MLPA using a very low amount of DNA. This managed to "dilute" the NUMT interference as well as enhance MLPA's efficiency. By this report, we conclude that when MLPA is performed upon a reduced amount of DNA, it can detect effectively mtDNA deletions. We propose MLPA as a possible first step method in the diagnosis of mt diseases.