Recurrent "outsider" intronic variation in the SLC5A6 gene causes severe mixed axonal and demyelinating neuropathy, cyclic vomiting and optic atrophy in 3 families from Maghreb

Sodium dependent multivitamin transporter (SMVT) deficiency is a very rare autosomal recessive disorder characterized by multisystemic clinical manifestations due to combined biotin, panthotenic acid and lipoic acid deficiency. About 10 families have been described so far. Accurate diagnosis is crucial because of the possibility of a supplementation treatment with proven efficacy. Here we describe 4 new patients (3 additional families) originating from the same world region (Algeria, Maghreb). All patients, born form consanguineous parents, were homozygous carriers of the same intronic variation, outside of canonical sites, in the SLC5A6 gene encoding SMVT. RNA study in one family allowed confirming the pathogenic effect of the variation and re-classifying this variant of uncertain significance as pathogenic, opening the possibility of genetic counseling and treatment. The identification of the same variation in three distinct and apparently unrelated families is suggestive of a founder effect. The phenotype of all patients was very similar, with systematic optic atrophy (initially considered as a very rare sign), severe cyclic vomiting, and rapidly progressive mixed axonal and demyelinating sensory motor neuropathy.

Spliceosome malfunction causes neurodevelopmental disorders with overlapping features

Pre-mRNA splicing is a highly coordinated process. While its dysregulation has been linked to neurological deficits, our understanding of the underlying molecular and cellular mechanisms remains limited. We implicated pathogenic variants in U2AF2 and PRPF19, encoding spliceosome subunits in neurodevelopmental disorders (NDDs), by identifying 46 unrelated individuals with 23 de novo U2AF2 missense variants (including 7 recurrent variants in 30 individuals) and 6 individuals with de novo PRPF19 variants. Eight U2AF2 variants dysregulated splicing of a model substrate. Neuritogenesis was reduced in human neurons differentiated from human pluripotent stem cells carrying two U2AF2 hyper-recurrent variants. Neural loss of function (LoF) of the Drosophila orthologs U2af50 and Prp19 led to lethality, abnormal mushroom body (MB) patterning, and social deficits, which were differentially rescued by wild-type and mutant U2AF2 or PRPF19. Transcriptome profiling revealed splicing substrates or effectors (including Rbfox1, a third splicing factor), which rescued MB defects in U2af50-deficient flies. Upon reanalysis of negative clinical exomes followed by data sharing, we further identified 6 patients with NDD who carried RBFOX1 missense variants which, by in vitro testing, showed LoF. Our study implicates 3 splicing factors as NDD-causative genes and establishes a genetic network with hierarchy underlying human brain development and function.

Comparison of cardiac involvement, extracardiac manifestations and outcomes between homozygote and heterozygote transthyretin p.Val142Ile (V122I) variant in patients with hereditary transthyretin amyloidosis: a cohort study

BACKGROUND

Hereditary transthyretin (ATTRv) p.Val142Ile (V122I) mutation is the most common inherited cause of cardiac amyloidosis and little is known about the phenotype and outcome of the rare homozygotic genotype. This study aimed to compare phenotypic characteristics and outcomes between heterozygous and homozygous patients with ATTRv V122I amyloidosis.

MATERIAL AND METHODS

This monocentric, observational, retrospective study conducted at the French National Referral Centre for Cardiac Amyloidosis (Henri Mondor Hospital, Créteil), described clinical, electrocardiographic, cardiac imaging features and prognostic data for patients with ATTRv V122I amyloidosis.

RESULTS

Among 185 ATTRv V122I patients identified, 161 were heterozygous and 24 were homozygous. The homozygous frequency was 13%. Onset occured significantly earlier in the homozygotes compared to heterozygotes with earlier median age at diagnosis (67[63-71] years vs 76[70-79] years, p < .001), age at first cardiac symptom (66[61-71] years vs 74[68-78] years, p < .001) and age at first extracardiac symptom (59[52-70] years vs 69[62-75] years, p = .003). Homozygous ATTRv V122I was also associated with greater disease burden with earlier events (death, transplant or hospitalisation for acute heart failure) compared with heterozygotes (71[67-74] vs 78[76-79] years, p = .018).

CONCLUSION

This rare, homozygous V122I cohort confirmed the earlier age of onset, death and cardiac events in this population.

[18F]FDG Positron emission tomography with whole body magnetic resonance imaging ([18F]FDG-PET/MRI) as a diagnosis tool in Schwannomatosis

Schwannomatosis is a rare autosomal dominant genetic syndrome characterized by the presence of multiple schwannomas. The main symptom is neurogenic pain. The diagnosis requires the presence of several schwannomas and whole-body ^[18F]FDG-PET/MRI might help detect extra schwannomas in patients when the diagnosis is uncertain. Among the 25 patients treated for Schwannomatosis in our tertiary center, three men and two women had had a ^[18F]FDG-PET/MRI performed, and the number of schwannomas detected by ^[18F]FDG-PET/MRI outnumbered the number of schwannomas suspected during the clinical examination. The majority of schwannomas exhibited a radiolabeling (median of 66.7%, range 28-93%). Our findings show that ^[18F]FDG-PET/MRI could prove useful when suspecting schwannomatosis to accelerate diagnosis and offer optimal care to patients.

Exome sequencing for diagnosis of congenital hemolytic anemia

Background

Congenital hemolytic anemia constitutes a heterogeneous group of rare genetic disorders of red blood cells. Diagnosis is based on clinical data, family history and phenotypic testing, genetic analyses being usually performed as a late step. In this study, we explored 40 patients with congenital hemolytic anemia by whole exome sequencing: 20 patients with hereditary spherocytosis and 20 patients with unexplained hemolysis.

Results

A probable genetic cause of disease was identified in 82.5% of the patients (33/40): 100% of those with suspected hereditary spherocytosis (20/20) and 65% of those with unexplained hemolysis (13/20). We found that several patients carried genetic variations in more than one gene (3/20 in the hereditary spherocytosis group, 6/13 fully elucidated patients in the unexplained hemolysis group), giving a more accurate picture of the genetic complexity of congenital hemolytic anemia. In addition, whole exome sequencing allowed us to identify genetic variants in non-congenital hemolytic anemia genes that explained part of the phenotype in 3 patients.

Conclusion

The rapid development of next generation sequencing has rendered the genetic study of these diseases much easier and cheaper. Whole exome sequencing in congenital hemolytic anemia could provide a more precise and quicker diagnosis, improve patients’ healthcare and probably has to be democratized notably for complex cases.

Central nervous system complications in adult cystinosis patients

Little is known about the long-term progression of adult nephropathic cystinosis patients. Our objective was to study central nervous system complications in cystinosis patients in the era of early cysteamine treatment, using advanced neuroimaging techniques. Neurological examination and multimodal brain 3 Tesla MRI were performed in 21 adult cystinosis patients, including 18 infantile cystinosis patients, 20 controls matched for age and renal function, and 12 healthy controls. Differences in gray matter volume and rest cerebral blood flow (CBF) using arterial spin labeling sequence were investigated using whole-brain voxel-based approach. Median age was 33.8 years (18.7-65.8). Seven patients (38.9%) presented with at least one central nervous system clinical abnormality: two (11.1%) with seizures, three (16.7%) with memory defects, five (27.8%) with cognitive defect, and one (5.5%) with stroke-like episode. These patients had a worse compliance to treatment (compliance score 2 vs 1, P = .03) and received a lower median cysteamine dose (0.9 g/day vs 2.1 g/day, P = .02). Among patients with infantile cystinosis, 13 (72.2%) showed cortical atrophy, which was absent in controls, but it was not correlated with symptoms. Cystinosis patients showed a significant gray matter decrease in the middle frontal gyrus compared with healthy controls and a significant negative correlation between the cystine blood level and rest CBF was observed in the right superior frontal gyrus, a region associated with executive function. Compliance to cysteamine treatment is a major concern in these adult patients and could have an impact on the development of neurological and cognitive complications.

Mutations in Complex I Assembly Factor TMEM126B Result in Muscle Weakness and Isolated Complex I Deficiency

Mitochondrial complex I deficiency results in a plethora of often severe clinical phenotypes manifesting in early childhood. Here, we report on three complex-I-deficient adult subjects with relatively mild clinical symptoms, including isolated, progressive exercise-induced myalgia and exercise intolerance but with normal later development. Exome sequencing and targeted exome sequencing revealed compound-heterozygous mutations in TMEM126B, encoding a complex I assembly factor. Further biochemical analysis of subject fibroblasts revealed a severe complex I deficiency caused by defective assembly. Lentiviral complementation with the wild-type cDNA restored the complex I deficiency, demonstrating the pathogenic nature of these mutations. Further complexome analysis of one subject indicated that the complex I assembly defect occurred during assembly of its membrane module. Our results show that TMEM126B defects can lead to complex I deficiencies and, interestingly, that symptoms can occur only after exercise.

New Method for Sorting Endothelial and Neural Progenitors from Human Induced Pluripotent Stem Cells by Sedimentation Field Flow Fractionation

Human induced pluripotent stem cells (hiPSc) are a very useful solution to create and observe the behavior of specific and usually inaccessible cells, such as human motor neurons. Obtained from a patient biopsy by reprograming dermal fibroblasts (DF), hiPSc present the same properties as embryonic stem cells and can generate any cell type after several weeks of differentiation. Today, there are numerus protocols which aim to control hiPSC differentiation. The principal challenge is to obtain a sufficiently enriched specific cell population to study disease pathophysiology and to provide a good model for further investigation and drug screening. The differentiation process is very costly and time-consuming, because many specific factors and different culture media must be used. In this study, we used Sedimentation Field Flow Fractionation (SdFFF) to prepare enriched populations derived from hiPSc after only 10 days of culture in a classical medium. Based on phenotypic and proteomic characterization, "hyperlayer" elution resulted in a fraction expressing markers of endothelial progenitors while another fraction expressed markers of neural progenitors. The isolation of subpopulations representing various differentiation lineages is of major interest for the production of specialized, cell-enriched fractions and in the preparation of increasingly complex models for the development of new therapeutic tools.

An exploratory randomised double-blind and placebo-controlled phase 2 study of a combination of baclofen, naltrexone and sorbitol (PXT3003) in patients with Charcot-Marie-Tooth disease type 1A

Background

Charcot-Marie-Tooth type 1A disease (CMT1A) is a rare orphan inherited neuropathy caused by an autosomal dominant duplication of a gene encoding for the structural myelin protein PMP22, which induces abnormal Schwann cell differentiation and dysmyelination, eventually leading to axonal suffering then loss and muscle wasting. We favour the idea that diseases can be more efficiently treated when targeting multiple disease-relevant pathways. In CMT1A patients, we therefore tested the potential of PXT3003, a low-dose combination of three already approved compounds (baclofen, naltrexone and sorbitol). Our study conceptually builds on preclinical experiments highlighting a pleiotropic mechanism of action that includes downregulation of PMP22. The primary objective was to assess safety and tolerability of PXT3003. The secondary objective aimed at an exploratory analysis of efficacy of PXT3003 in CMT1A, to be used for designing next clinical development stages (Phase 2b/3).

Methods

80 adult patients with mild-to-moderate CMT1A received in double-blind for 1 year Placebo or one of the three increasing doses of PXT3003 tested, in four equal groups. Safety and tolerability were assessed with the incidence of related adverse events. Efficacy was assessed using the Charcot-Marie-Tooth Neuropathy Score (CMTNS) and the Overall Neuropathy Limitations Scale (ONLS) as main endpoints, as well as various clinical and electrophysiological outcomes.

Results

This trial confirmed the safety and tolerability of PXT3003. The highest dose (HD) showed consistent evidence of improvement beyond stabilization. CMTNS and ONLS, with a significant improvement of respectively of 8% (0.4% - 16.2%) and 12.1% (2% - 23.2%) in the HD group versus the pool of all other groups, appear to be the most sensitive clinical endpoints to treatment despite their quasi-stability over one year under Placebo. Patients who did not deteriorate over one year were significantly more frequent in the HD group.

Conclusions

These results confirm that PXT3003 deserves further investigation in adults and could greatly benefit CMT1A-diagnosed children, usually less affected than adults.

Trial registration

EudraCT Number: 2010-023097-40. ClinicalTrials.gov Identifier: NCT01401257. The Committee for Orphan Medicinal Products issued in February 2014 a positive opinion on the application for orphan designation for PXT3003 (EMA/OD/193/13).

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-014-0199-0) contains supplementary material, which is available to authorized users.

Insulin-Like Growth Factor-I, Insulin-Like Growth factor Binding Protein-3 and Blood Hemoglobin Concentration in an Elderly Population

BACKGROUND

Insulin-like growth factor-I (IGF-I) serum level decreases with age, and this decrease may underlie hemoglobin (Hb) decrease. The objective of the study was to assess the relationship between IGF-I and insulin-like growth factor binding protein-3 (IGFBP-3) serum levels and Hb, after adjustment especially for major nutritional factors in an elderly population because IGF-I system depends on nutritional state, often impaired in the elderly.

METHODS

Hemoglobin concentration was tested for 672 participants evaluated during an outpatient geriatric assessment. IGF-I and IGFBP-3 serum levels were assessed by Enzyme Linked Immunosorbent Assay. The molar ratio of IGF-I/IGFBP-3 that reflects the bioavailable IGF-I was calculated. Levels of IGF-I and IGFBP-3 were plotted against quartiles of Hb. Final linear models for IGF-I, IGFBP-3 and ratio molar included factors that could modify the Hb level.

RESULTS

Mean age (SD) of the sample was 78.0 (8.5) years old and 32% were men. After adjustment for age and sex, IGF-I serum level, IGFBP-3 serum level and molar ratio significantly increased with increasing quartiles of Hb. After adjustment for age, gender, diabetes, albumin, pre-albumin, renal function, total cholesterol, angiotensin converting enzyme inhibitors and angiotensin II receptor blockers consumption, C-Reactive Protein, Hb was significantly associated and with IGF-I level (p = .002) and molar ratio (p = .02).

CONCLUSIONS

IGF-I serum level and IGF-I/IGFBP-3 molar ratio were associated with Hb in an elderly population, independently of nutritional biological parameters. Thus, the association between the IGF-I system and Hb merits further investigation to determine whether interventions that modulate circulating IGF-I or IGF-I/BP3 ratio might preserve Hb in the elderly.

A reversible functional sensory neuropathy model

Small-fiber neuropathy was induced in young adult mice by intraperitoneal injection of resiniferatoxin (RTX), a TRPV1 agonist. At day 7, RTX induced significant thermal and mechanical hypoalgesia. At day 28, mechanical and thermal nociception were restored. No nerve degeneration in skin was observed and unmyelinated nerve fiber morphology and density in sciatic nerve were unchanged. At day 7, substance P (SP) was largely depleted in dorsal root ganglia (DRG) neurons, although calcitonin gene-related peptide (CGRP) was only moderately depleted. Three weeks after, SP and CGRP expression was restored in DRG neurons. At the same time, CGRP expression remained low in intraepidermal nerve fibers (IENFs) whereas SP expression had improved. In summary, RTX induced in our model a transient neuropeptide depletion in sensory neurons without nerve degeneration. We think this model is valuable as it brings the opportunity to study functional nerve changes in the very early phase of small fiber neuropathy. Moreover, it may represent a useful tool to study the mechanisms of action of therapeutic strategies to prevent sensory neuropathy of various origins.

A leaky splicing mutation affecting SMN1 exon 7 inclusion explains an unexpected mild case of spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder resulting, in most cases, from homozygous deletions of the SMN1 gene or, in rare cases, from SMN1 intragenic mutations. Here we describe the identification and characterization of c.835-3C>T, a novel SMA-causing mutation detected in the intron 6 of the single SMN1 allele of a type IV SMA patient. We demonstrate both ex vivo and in vivo that c.835-3C>T is a deleterious splicing mutation that induces a modest but unequivocal exclusion of exon 7 from the SMN1 transcripts, its "leakiness" explaining the exceptionally mild phenotype of this patient. This mutation creates a putative high-affinity binding site for the splicing repressor protein hnRNP A1 overlapping the splice acceptor site of exon 7 (UAG|GGU). Our findings support the current therapeutic strategies aiming at correcting exon 7 splicing in SMA patients, and bring clues about the level of exon 7 inclusion required to achieve a therapeutic effect.

CMT4D (NDRG1 mutation): genotype-phenotype correlations

Charcot-Marie-Tooth (CMT) disease is a heterogeneous condition with a large number of clinical, electrophysiological and pathological phenotypes. More than 40 genes are involved. We report a child of gypsy origin with an autosomal recessive demyelinating phenotype. Clinical data, familial history, and electrophysiological studies were in favor of a CMT4 sub-type. The characteristic N-Myc downstream-regulated gene 1 (NDRG1) mutation responsible for this CMT4D phenotype was confirmed: p.R148X. The exact molecular function of the NDRG1 protein has yet to be elucidated.

Characterization of Endoneurial Fibroblast-like Cells from Human and Rat Peripheral Nerves

Endoneurial fibroblast-like cells (EFLCs) are one of the cell populations present in the peripheral nervous system. The role and immunophenotypic characteristics of EFLCs are not well known and led us to perform a histological and cytological study of EFLCs in normal human and rat peripheral nerves. We found that all EFLCs express CD34, neural/glial antigen 2 (NG2), and prolyl-4-hydrolase-beta. In addition, half of the EFLCs in normal peripheral nerves express platelet-derived growth factor receptor-β (PDGFR-β) and some also express the intermediate filament nestin in vivo (at a lower level than Schwann cells, which express high levels of nestin). Using cell cultures of purified EFLCs, we characterized subpopulations of EFLCs expressing PDGFR-β alone or PDGFR-β and nestin. Experimental nerve lesions in rat resulted in an increase in nestin-positive EFLCs, which returned to normal levels after 8 days. This suggests that some EFLCs could have a different proliferative and/or regenerative potential than others, and these EFLCs may play a role in the initial phase of nerve repair. These "activated" EFLCs share some immunophenotypic similarities with pericytes and Interstitial cells of Cajal, which have progenitor cell potentials. This raises the questions as to whether a proportion of EFLCs have a possible role as endoneurial progenitor cells.

Insulin-like growth factor I, insulin-like growth factor binding protein 3, and atrial fibrillation in the elderly

BACKGROUND

Insulin-like growth factor I (IGF-I) and insulin-like growth factor binding protein 3 (IGFBP-3) are involved in oxidative stress and atherosclerosis; however, the relationship between the IGF-I system and atrial fibrillation (AF) is not known. The objective of this analysis was to assess, the relationship between IGF-I and IGFBP-3 serum levels and AF among elderly participants.

METHODS

In this cross-sectional study, 719 participants (mean age [SD] years: 78.2 [6.8]; 31.8% men) were evaluated during an outpatient geriatric assessment. AF was determined by electrocardiogram or medical record. Participants were classified into two groups: Participants with AF (n = 91) or without AF (n = 628). IGF-I and IGFBP-3 serum levels were determined by enzyme linked immunosorbent assay.

RESULTS

After adjusting for age and sex, the mean IGF-I and IGFBP-3 serum levels were significantly lower among AF participants than among non-AF participants (mean IGF-I ng/mL [SD] = 133.8 [66.6] vs 157.9 [80.0], p = .02; mean IGFBP-3 ng/mL [SD] = 3,653 [1,393] vs 4,151 [1,583], p = .03, respectively). After adjusting for confounding factors (age, gender, beta blocker medication, heart rate, hypertension, stroke, and chronic heart failure), low IGF-I serum level (OR [95% CI] = 0.66 [0.49-0.87]) and low IGFBP-3 serum level (0.71 [0.54-0.93]) remained independent determinants of AF.

CONCLUSIONS

Low IGF-I and low IGFBP-3 serum levels were independently associated with AF in this elderly population. This result should be confirmed in a longitudinal study to evaluate whether IGF-I and/or IGFBP-3 serum levels are predictive of incident AF.

Two novel mutations of the calcium-sensing receptor gene affecting the same amino acid position lead to opposite phenotypes and reveal the importance of p.N802 on receptor activity

OBJECTIVE

Gain-of-function mutations of the calcium-sensing receptor (CASR) gene have been identified in patients with sporadic or familial autosomal dominant hypocalcemia (ADH). Inactivating mutations of the CASR gene cause familial hypocalciuric hypercalcemia (FHH). Here, we report two novel CASR mutations affecting the same amino acid (p.N802); one causes ADH and the other atypical FHH.

PATIENTS AND METHODS

The first patient, an 11-year-old girl suffering from hypocalcemia, developed nephrocalcinosis when she was only 5 years old. The second patient is a 30-year-old woman who presented with mild hypercalcemia. PCR amplification of CASR coding exons and direct sequencing of PCR products were used to identify mutations. Site-directed mutagenesis was used to generate mutated CASR cDNAs in an expression plasmid. Using the MAPK assay system and transient transfection of Cos-7 cells with wild-type (WT) and mutated CASR, we studied the responses of these mutated receptors to extracellular Ca(2+) and to the negative allosteric CASR modulator, NPS2143.

RESULTS

Two heterozygous missense mutations (p.N802I and p.N802S) affecting a residue in the sixth transmembrane domain of CASR were identified. In functional tests, the response of the p.N802S mutant to calcium was typical of an inactivating mutation. However, the p.N802I mutant had 70% of the maximally stimulated WT receptor activity even in the absence of extracellular calcium. This constitutive activity was only partially inhibited by the inhibitor, NPS2143.

CONCLUSIONS

The asparagine at amino acid position 802 appears to be essential for the activity of the CASR protein and is implicated in the mechanism of CASR signaling.

Insulin-like growth factor-I and insulin-like growth factor binding protein-3 in Alzheimer's disease

CONTEXT

Few large studies have been conducted to assess the relationship between circulating IGF and late-life cognition.

OBJECTIVE

The aim of the study was to assess the relationship between IGF-I and IGF binding protein-3 (IGFBP-3) serum levels and cognitive impairment, including Alzheimer's disease (AD).

METHODS

In this multicentric cross-sectional study, 694 elderly subjects (218 men, 476 women; 78.6 ± 6.7 yr old) were included; 481 had memory complaints and were diagnosed, after comprehensive cognitive assessment, with AD (n = 224) or mild cognitive impairment (MCI) (n = 257). The control group was comprised of 213 subjects without memory complaint and with normal cognition (recruited among patients' caregivers). IGF-I and IGFBP-3 serum levels were determined by ELISA.

RESULTS

IGF-I and IGFBP-3 serum levels were significantly associated with cognitive status in men (IGF-I, 137 ± 69 ng/ml for AD vs. 178 ± 88 ng/ml for MCI and 172 ± 91 ng/ml for controls, P = 0.01; IGFBP-3, 3675 ± 1542 ng/ml for AD vs. 4143 ± 1828 ng/ml for MCI and 4488 ± 1893 ng/ml for controls, P = 0.04). In women, IGFBP-3 was significantly associated with cognitive status (3781 ± 1351 ng/ml for AD vs. 4190 ± 1408 ng/ml for MCI and 4390 ± 1552 ng/ml for controls; P < 0.001), but no significant differences between groups for IGF-I occurred. After adjustment for confounding variables (age, educational level, body mass index, diabetes, apolipoprotein E ε4 status), logistic regression indicated that IGF-I [odds ratio (95% confidence interval) = 0.48 (0.26-0.88)] and IGFBP-3 [odds ratio (95% confidence interval) = 0.71 (0.52-0.97)] serum levels were independently associated with AD in men, but not in women.

CONCLUSIONS

We report a significant association between low IGF-I and IGFBP-3 serum levels and AD in men, but not in women.

[Familial amyloidotic polyneuropathies]

Transthyretin familial amyloid polyneuropathy (TTRFAP) is an autosomal dominant neuropathy that is fatal within about 10 years after symptom onset. TTRFAP is observed worldwide, albeit with a higher frequency of the most common variant, Val30met, in Portugal, Sweden and Japan. Various phenotypic differences are observed. TTRFAP should be considered in patients with a progressive axonal polyneuropathy of unknown origin, especially when associated with autonomic nervous system dysfunction. A positive family history is found in most cases when onset begins around 30 years of age, while late-onset FAP is often sporadic and may be confused with chronic inflammatory demyelinating polyneuropathy. Nerve biopsy is often used to confirm the presence of extracellular amyloid deposits in interstitial tissue of the endoneurial space, although amyloid can also befound in muscle, salivary gland and abdominal fat. It is important to stress that biopsy negativity does not rule out amyloidosis. Genetic testing for TTR gene mutations should be performed in case of progressive length-dependent axonal polyneuropathy predominantly involving small nerve fibers.

FLNA genomic rearrangements cause periventricular nodular heterotopia

OBJECTIVE

To identify copy number variant (CNV) causes of periventricular nodular heterotopia (PNH) in patients for whom FLNA sequencing is negative.

METHODS

Screening of 35 patients from 33 pedigrees on an Affymetrix 6.0 microarray led to the identification of one individual bearing a CNV that disrupted FLNA. FLNA-disrupting CNVs were also isolated in 2 other individuals by multiplex ligation probe amplification. These 3 cases were further characterized by high-resolution oligo array comparative genomic hybridization (CGH), and the precise junctional breakpoints of the rearrangements were identified by PCR amplification and sequencing.

RESULTS

We report 3 cases of PNH caused by nonrecurrent genomic rearrangements that disrupt one copy of FLNA. The first individual carried a 113-kb deletion that removes all but the first exon of FLNA. A second patient harbored a complex rearrangement including a deletion of the 3' end of FLNA accompanied by a partial duplication event. A third patient bore a 39-kb deletion encompassing all of FLNA and the neighboring gene EMD. High-resolution oligo array CGH of the FLNA locus suggests distinct molecular mechanisms for each of these rearrangements, and implicates nearby low copy repeats in their pathogenesis.

CONCLUSIONS

These results demonstrate that FLNA is prone to pathogenic rearrangements, and highlight the importance of screening for CNVs in individuals with PNH lacking FLNA point mutations.

Early onset Parkinsonism associated with an intronic SOD1 mutation

We report on a patient belonging to a large family with autosomal-dominant amyotrophic lateral sclerosis, who developed asymmetrical akineto-rigid symptoms at 33 years of age. He had no signs of lower motor neuron disease after four years of follow-up. All seven ALS patients from this family harboured a mutation located in the fourth intron of the SOD1 gene. The proband also harboured the same mutation, associated with a 40% decrease in SOD1 erythrocyte activity. This case report suggests that SOD1 mutations might be associated with marked phenotypic variability (ALS or early onset Parkinsonism in this family).

How can grafted breast cancer models be optimized?

Breast cancer is the most frequent spontaneous malignancy diagnosed in women and is characterized by a broad histological diversity. Progression of the disease has a metastasizing trend and can be resistant to hormonal and chemotherapy. Animal models have provided some understanding of these features and have allowed new treatments to be proposed. However, these models need to be revised because they have some limitations in predicting the clinical efficacy of new therapies. In this review, we discuss the biological criteria to be taken into account for a realistic animal model of breast cancer graft (tumor implantation site, animal immune status, histological diversity, modern imaging). We emphasize the need for more stringent monitoring criteria, and suggest adopting the human RECIST (Response Evaluation Criteria in Solid Tumors) criteria to evaluate treatments in animal models.

Nerve biopsy: requirements for diagnosis and clinical value

In many instances, nerve biopsy is not necessary in the diagnostic work-up of a peripheral neuropathy. However, histological examination of a tissue sample is still mandatory to show specific lesions in various conditions involving peripheral nerves. As there are fewer laboratories that examine human nerve samples, practitioners including neurologists and general pathologists may not be completely aware of the technical issues and data that are provided by nerve biopsy. Nerve biopsy is considered an invasive diagnostic method, although, its complications are by far less disabling than most of the disorders that lead to its indications. Nevertheless, the decision to perform a nerve biopsy has to be made on a case-by-case basis, and its results must be discussed between the pathologist and the clinician who is in charge of the patient's care. In this paper, we review the minimal technical requirements for proper peripheral nerve tissue analysis. Moreover, we provide data on the usefulness of nerve biopsy in various situations including abnormal deposits, cell infiltrates, link between peripheral neuropathy and monoclonal gammopathy, and numerous hereditary disorders.

Krox20 inactivation in the PNS leads to CNS/PNS boundary transgression by central glia

CNS/PNS interfaces constitute cell boundaries, since they delimit territories with different neuronal and glial contents. Despite their potential interest in regenerative medicine, the mechanisms restricting oligodendrocytes and astrocytes to the CNS, and Schwann cells to the PNS in mammals are not known. To investigate the involvement of peripheral glia and myelin in the maintenance of the CNS/PNS boundary, we have first made use of different mouse mutants. We show that inactivation of Krox20/Egr2, a master regulatory gene for myelination in Schwann cells, results in transgression of the CNS/PNS boundary by astrocytes and oligodendrocytes and in myelination of nerve root axons by oligodendrocytes. In contrast, such migration does not occur with the Trembler(J) mutation, which prevents PNS myelination without affecting Krox20 expression. Altogether these data suggest that maintenance of the CNS/PNS boundary requires a new Krox20 function separable from myelination control. Finally, we have analyzed a human patient affected by a congenital amyelinating neuropathy, associated with the absence of the KROX20 protein in Schwann cells. In this case, the nerve roots were also invaded by oligodendrocytes and astrocytes. This indicates that transgression of the CNS/PNS boundary by central glia can occur in pathological situations in humans and suggests that the underlying mechanisms are common with the mouse.