Affected female carriers of MTM1 mutations display a wide spectrum of clinical and pathological involvement: delineating diagnostic clues.

X-linked myotubular myopathy (XLMTM), a severe congenital myopathy, is caused by mutations in the MTM1 gene located on the X chromosome. A majority of affected males die in the early postnatal period, whereas female carriers are believed to be usually asymptomatic. Nevertheless, several affected females have been reported. To assess the phenotypic and pathological spectra of carrier females and to delineate diagnostic clues, we characterized 17 new unrelated affected females and performed a detailed comparison with previously reported cases at the clinical, muscle imaging, histological, ultrastructural and molecular levels. Taken together, the analysis of this large cohort of 43 cases highlights a wide spectrum of clinical severity ranging from severe neonatal and generalized weakness, similar to XLMTM male, to milder adult forms. Several females show a decline in respiratory function. Asymmetric weakness is a noteworthy frequent specific feature potentially correlated to an increased prevalence of highly skewed X inactivation. Asymmetry of growth was also noted. Other diagnostic clues include facial weakness, ptosis and ophthalmoplegia, skeletal and joint abnormalities, and histopathological signs that are hallmarks of centronuclear myopathy such as centralized nuclei and necklace fibers. The histopathological findings also demonstrate a general disorganization of muscle structure in addition to these specific hallmarks. Thus, MTM1 mutations in carrier females define a specific myopathy, which may be independent of the presence of an XLMTM male in the family. As several of the reported affected females carry large heterozygous MTM1 deletions not detectable by Sanger sequencing, and as milder phenotypes present as adult-onset limb-girdle myopathy, the prevalence of this myopathy is likely to be greatly underestimated. This report should aid diagnosis and thus the clinical management and genetic counseling of MTM1 carrier females. Furthermore, the clinical and pathological history of this cohort may be useful for therapeutic projects in males with XLMTM, as it illustrates the spectrum of possible evolution of the disease in patients surviving long term.

Type I interferon potentiates T-cell receptor mediated induction of IL-10-producing CD4⁺ T cells.

Type I interferons (IFNs) have the dual ability to promote the development of the immune response and exert an anti-inflammatory activity. We analyzed the integrated effect of IFN-α, TCR signal strength, and CD28 costimulation on human CD4⁺ T-cell differentiation into cell subsets producing the anti- and proinflammatory cytokines IL-10 and IFN-γ. We show that IFN-α boosted TCR-induced IL-10 expression in activated peripheral CD45RA⁺CD4⁺ T cells and in whole blood cultures. The functional cooperation between TCR and IFN-α efficiently occurred at low engagement of receptors. Moreover, IFN-α rapidly cooperated with anti-CD3 stimulation alone. IFN-α, but not IL-10, drove the early development of type I regulatory T cells that were mostly IL-10⁺ Foxp3⁻ IFN-γ⁻ and favored IL-10 expression in a fraction of Foxp3⁺ T cells. Our data support a model in which IFN-α costimulates TCR toward the production of IL-10 whose level can be amplified via an autocrine feedback loop.

Palmo-Plantar hyperkeratosis, intellectual disability, and spastic paraplegia in two maternal half brothers: further evidence for an X-linked inheritance.

In 1983, Fitzsimmons et al. reported four brothers with an unrecognized disorder characterized by intellectual disability, spastic paraplegia, and palmo-plantar hyperkeratosis (OMIM 309500). In this report, we describe a family in which two males, maternal half-brothers, had learning disabilities. Both patients also showed spasticity in the lower limbs and palmo-plantar hyperkeratosis. The mother of the affected boys had learning difficulties but did not show any dermatological symptoms. This report confirms that the association of features reported by Fitzsimmons et al. is a distinct entity and further suggests an X-linked mode of inheritance.

Infection-triggered familial or recurrent cases of acute necrotizing encephalopathy caused by mutations in a component of the nuclear pore, RANBP2.

Acute necrotizing encephalopathy (ANE) is a rapidly progressive encephalopathy that can occur in otherwise healthy children after common viral infections such as influenza and parainfluenza. Most ANE is sporadic and nonrecurrent (isolated ANE). However, we identified a 7 Mb interval containing a susceptibility locus (ANE1) in a family segregating recurrent ANE as an incompletely penetrant, autosomal-dominant trait. We now report that all affected individuals and obligate carriers in this family are heterozygous for a missense mutation (c.1880C-->T, p.Thr585Met) in the gene encoding the nuclear pore protein Ran Binding Protein 2 (RANBP2). To determine whether this mutation is the susceptibility allele, we screened controls and other patients with ANE who are unrelated to the index family. Patients from 9 of 15 additional kindreds with familial or recurrent ANE had the identical mutation. It arose de novo in two families and independently in several other families. Two other patients with familial ANE had different RANBP2 missense mutations that altered conserved residues. None of the three RANBP2 missense mutations were found in 19 patients with isolated ANE or in unaffected controls. We conclude that missense mutations in RANBP2 are susceptibility alleles for familial and recurrent cases of ANE.

Ring 14 chromosome presenting as early-onset isolated partial epilepsy.

We report four infants (two males, two females) with ring 14 chromosome presenting with early-onset partial epilepsy. The first seizure occurred between 3 and 6 months (3, 3, 4, and 6mo respectively). In all four cases, diagnosis was based on early focal seizures, rather than on psychomotor retardation or morphological features, which were not prominent at seizure onset. Moreover, despite the young age of the patients and the high frequency of seizures, neither epileptic spasms nor progression to 'epileptic encephalopathy', such as hypsarrhythmia, were observed. Epilepsy remained partial in these patients. At the most recent follow-up, all four children had slight or mild psychomotor delay, and two of them had moderate non-specific dysmorphic traits. Data from the literature about epilepsy in ring 14 chromosome syndrome were also reviewed. Ring 14 chromosome syndrome may be revealed by isolated, early-onset focal epilepsy suggestive of focal lesions with only mild mental retardation and morphological features at the time of diagnosis. The characteristics of these observations differ from classic ring 14 syndrome, and may enlarge this clinical spectrum. Many unanswered questions remain concerning phenotype-genotype correlation and identification of the potential genes and molecular mechanisms responsible for epilepsy in patients with ring 14 syndrome.

Identification of an in vivo orally active dual-binding protein-protein interaction inhibitor targeting TNFα through combined in silico/in vitro/in vivo screening.

TNFα is a homotrimeric pro-inflammatory cytokine, whose direct targeting by protein biotherapies has been an undeniable success for the treatment of chronic inflammatory diseases. Despite many efforts, no orally active drug targeting TNFα has been identified so far. In the present work, we identified through combined in silico/in vitro/in vivo approaches a TNFα direct inhibitor, compound 1, displaying nanomolar and micromolar range bindings to TNFα. Compound 1 inhibits the binding of TNFα with both its receptors TNFRI and TNFRII. Compound 1 inhibits the TNFα induced apoptosis on L929 cells and the TNFα induced NF-κB activation in HEK cells. In vivo, oral administration of compound 1 displays a significant protection in a murine TNFα-dependent hepatic shock model. This work illustrates the ability of low-cost combined in silico/in vitro/in vivo screening approaches to identify orally available small-molecules targeting challenging protein-protein interactions such as homotrimeric TNFα.

Clinical and electrophysiological features in a French family presenting with seipinopathy.

Seipinopathies are a group of inherited diseases affecting upper and lower motor neurons due to mutations in the Berardinelli-Seip congenital lipodystrophy 2 gene (BSCL2). We report a French family carrying the N88S mutation in the BSCL2 gene. A 12-yr-old girl complained of bilateral asymmetrical pes cavus with right hand motor deficit and amyotrophy, asymmetrical leg amyotrophy and pyramidal signs. Electrophysiological examination showed axonal asymmetrical motor neuropathy with distal predominance. Her father complained of right hand rest tremor with bilateral hand weakness. Physical examination revealed left leg, hand and forearm amyotrophy, akinesia and right arm rigidity, brisk reflexes in the lower limbs and bilateral Babinski sign. Nerve conduction studies showed distal asymmetrical axonal neuropathy with slight sensitive impairment with moderate decrease of nerve conduction velocity in some nerves. DNA sequencing revealed the presence of the known N88S mutation in the BSCL2 gene (dideoxy-nucleotide method on a 3730 DNA Analyzer, Life Technologies). BSCL2 gene mutations are associated with a wide spectrum of clinical and electrophysiological phenotypes and should be suspected in cases of distal hereditary motor neuropathy with pyramidal signs or early hand involvement. There may also be associated mild demyelination which may vary in severity within the same family. Clinical diagnosis was more difficult in this particular case due to the association with Parkinson symptoms.

Expanding the clinical spectrum of hereditary fibrosing poikiloderma with tendon contractures, myopathy and pulmonary fibrosis due to FAM111B mutations.

BACKGROUND: Hereditary Fibrosing Poikiloderma (HFP) with tendon contractures, myopathy and pulmonary fibrosis (POIKTMP [MIM 615704]) is a very recently described entity of syndromic inherited poikiloderma. Previously by using whole exome sequencing in five families, we identified the causative gene, FAM111B (NM_198947.3), the function of which is still unknown. Our objective in this study was to better define the specific features of POIKTMP through a larger series of patients. METHODS: Clinical and molecular data of two families and eight independent sporadic cases, including six new cases, were collected. RESULTS: Key features consist of: (i) early-onset poikiloderma, hypotrichosis and hypohidrosis; (ii) multiple contractures, in particular triceps surae muscle contractures; (iii) diffuse progressive muscular weakness; (iv) pulmonary fibrosis in adulthood and (v) other features including exocrine pancreatic insufficiency, liver impairment and growth retardation. Muscle magnetic resonance imaging was informative and showed muscle atrophy and fatty infiltration. Histological examination of skeletal muscle revealed extensive fibroadipose tissue infiltration. Microscopy of the skin showed a scleroderma-like aspect with fibrosis and alterations of the elastic network. FAM111B gene analysis identified five different missense variants (two recurrent mutations were found respectively in three and four independent families). All the mutations were predicted to localize in the trypsin-like cysteine/serine peptidase domain of the protein. We suggest gain-of-function or dominant-negative mutations resulting in FAM111B enzymatic activity changes. CONCLUSIONS: HFP with tendon contractures, myopathy and pulmonary fibrosis, is a multisystemic disorder due to autosomal dominant FAM111B mutations. Future functional studies will help in understanding the specific pathological process of this fibrosing disorder.

Similar early characteristics but variable neurological outcome of patients with a de novo mutation of KCNQ2.

BACKGROUND: Early onset epileptic encephalopathies (EOEEs) are dramatic heterogeneous conditions in which aetiology, seizures and/or interictal EEG have a negative impact on neurological development. Several genes have been associated with EOEE and a molecular diagnosis workup is challenging since similar phenotypes are associated with mutations in different genes and since mutations in one given gene can be associated with very different phenotypes. Recently, de novo mutations in KCNQ2, have been found in about 10% of EOEE patients. Our objective was to confirm that KCNQ2 was an important gene to include in the diagnosis workup of EOEEs and to fully describe the clinical and EEG features of mutated patients. METHODS: We have screened KCNQ2 in a cohort of 71 patients with an EOEE, without any brain structural abnormality. To be included in the cohort, patient's epilepsy should begin before three months of age and be associated with abnormal interictal EEG and neurological impairment. Brain MRI should not show any structural abnormality that could account for the epilepsy. RESULTS: Out of those 71 patients, 16 had a de novo mutation in KCNQ2 (23%). Interestingly, in the majority of the cases, the initial epileptic features of these patients were comparable to those previously described in the case of benign familial neonatal epilepsy (BFNE) also caused by KCNQ2 mutations. However, in contrast to BFNE, the interictal background EEG was altered and displayed multifocal spikes or a suppression-burst pattern. The ongoing epilepsy and development were highly variable but overall severe: 15/16 had obvious cognitive impairment, half of the patients became seizure-free, 5/16 could walk before the age of 3 and only 2/16 patient acquired the ability to speak. CONCLUSION: This study confirms that KCNQ2 is frequently mutated de novo in neonatal onset epileptic encephalopathy. We show here that despite a relatively stereotyped beginning of the condition, the neurological and epileptic evolution is variable.