Impact of restricted access to, and low awareness of, mexiletine on people with myotonia: a real-world European survey

Although mexiletine effectively treats myotonia, supply disruptions affected Europe between 2008-2018. MyoPath was a mixed-methods, cross-sectional, market research survey conducted January-June 2018 to evaluate consequences of limited access to/awareness of mexiletine in people with myotonia. Part A: qualitative structured interviews (clinicians; advocates for adult patients); Part B: quantitative online questionnaire completed by people with self-reported history of myotonia. Part A: Interviews (clinicians, n=12; patient advocates, n=5; 12 countries) indicated poor mexiletine awareness among general neurologists. Patients chose between living with myotonia (other treatments were generally unsatisfactory) or importing mexiletine. Part B: Questionnaire respondents, myotonic dystrophy (DM)1, n=213; DM2, n=128; non-dystrophic myotonia (NDM), n=41; other n=8; (11 countries). Of the respondents, 76/390 (20%) people with awareness of/access to mexiletine described profound improvements in myotonia and health-related quality of life following treatment. Respondents with NDM had greatest mexiletine experience (n=28/41). Mexiletine was associated with fewer falls, less muscle stiffness, increased mobility. Treatment interruptions worsened myotonia and were associated with fatigue, pain, dysphagia, breathing difficulty, impaired digestion, poor sleep. However, 36/54 (67%) of currently treated people expressed anxiety about mexiletine's availability: this finding was expected (MyoPath was undertaken before mexiletine's approval in NDM). MyoPath provides the largest European exploration of patients' views regarding impact of mexiletine on myotonia. Anticipated effects of mexiletine differ between people with different myotonic disorders: myotonia is the main symptom in NDM but one of many potential symptoms affecting those with DM. Nevertheless, findings indicate substantial harm caused to people with myotonia when mexiletine awareness/access is limited.

Heterogeneity of resting-state EEG features in juvenile myoclonic epilepsy and controls

Abnormal EEG features are a hallmark of epilepsy, and abnormal frequency and network features are apparent in EEGs from people with idiopathic generalized epilepsy in both ictal and interictal states. Here, we characterize differences in the resting-state EEG of individuals with juvenile myoclonic epilepsy and assess factors influencing the heterogeneity of EEG features. We collected EEG data from 147 participants with juvenile myoclonic epilepsy through the Biology of Juvenile Myoclonic Epilepsy study. Ninety-five control EEGs were acquired from two independent studies [Chowdhury et al. (2014) and EU-AIMS Longitudinal European Autism Project]. We extracted frequency and functional network-based features from 10 to 20 s epochs of resting-state EEG, including relative power spectral density, peak alpha frequency, network topology measures and brain network ictogenicity: a computational measure of the propensity of networks to generate seizure dynamics. We tested for differences between epilepsy and control EEGs using univariate, multivariable and receiver operating curve analysis. In addition, we explored the heterogeneity of EEG features within and between cohorts by testing for associations with potentially influential factors such as age, sex, epoch length and time, as well as testing for associations with clinical phenotypes including anti-seizure medication, and seizure characteristics in the epilepsy cohort. P-values were corrected for multiple comparisons. Univariate analysis showed significant differences in power spectral density in delta (2-5 Hz) (P = 0.0007, hedges' g = 0.55) and low-alpha (6-9 Hz) (P = 2.9 × 10-8, g = 0.80) frequency bands, peak alpha frequency (P = 0.000007, g = 0.66), functional network mean degree (P = 0.0006, g = 0.48) and brain network ictogenicity (P = 0.00006, g = 0.56) between epilepsy and controls. Since age (P = 0.009) and epoch length (P = 1.7 × 10-8) differed between the two groups and were potential confounders, we controlled for these covariates in multivariable analysis where disparities in EEG features between epilepsy and controls remained. Receiver operating curve analysis showed low-alpha power spectral density was optimal at distinguishing epilepsy from controls, with an area under the curve of 0.72. Lower average normalized clustering coefficient and shorter average normalized path length were associated with poorer seizure control in epilepsy patients. To conclude, individuals with juvenile myoclonic epilepsy have increased power of neural oscillatory activity at low-alpha frequencies, and increased brain network ictogenicity compared with controls, supporting evidence from studies in other epilepsies with considerable external validity. In addition, the impact of confounders on different frequency-based and network-based EEG features observed in this study highlights the need for careful consideration and control of these factors in future EEG research in idiopathic generalized epilepsy particularly for their use as biomarkers.

Application of synthetic photostable retinoids induces novel limb and facial phenotypes during chick embryogenesis in vivo

We have recently developed a range of synthetic retinoid analogues which include the compounds EC23 and EC19. They are stable on exposure to light and are predicted to be resistant to the normal metabolic processes involved in the inactivation of retinoids in vivo. Based on the position of the terminal carboxylic acid groups in the compounds we suggest that EC23 is a structural analogue of all-trans retinoic acid (ATRA), and EC19 is an analogue of 13-cis retinoic acid. Their effects on the differentiation of pluripotent stem cells has been previously described in vitro and are consistent with this hypothesis. We present herein the first description of the effects of these molecules in vivo. Retinoids were applied to the anterior limb buds of chicken embryos in ovo via ion-exchange beads. We found that retinoid EC23 produces effects on the wing digits similar to ATRA, but does so at two orders of magnitude lower concentration. When larger quantities of EC23 are applied, a novel phenotype is obtained involving production of multiple digit 1s on the anterior limb. This corresponds to differential effects of ATRA and EC23 on sonic hedgehog (shh) expression in the developing limb bud. With EC23 application we also find digit 1 phenotypes similar to thumb duplications described in the clinical literature. EC23 and ATRA are shown to have effects on the entire proximal–distal axis of the limb, including hitherto undescribed effects on the scapula. This includes suppression of expression of the scapula marker Pax1. EC23 also produces effects similar to those of ATRA on the developing face, producing reductions of the upper beak at concentrations two orders of magnitude lower than ATRA. In contrast, EC19, which is structurally very similar to EC23, has novel, less severe effects on the face and rarely alters limb development. EC19 and ATRA are effective at similar concentrations. These results further demonstrate the ability of retinoids to influence embryonic development. Moreover, EC23 represents a useful new tool to investigate developmental processes and probe the mechanisms underlying congenital abnormalities in vertebrates including man.

Lack of association between beta 2-adrenergic receptor polymorphisms and juvenile idiopathic arthritis

OBJECTIVE

Juvenile idiopathic arthritis (JIA) is a chronic autoimmune arthropathy. Beta 2-adrenergic receptors are a link between the sympathetic nervous system and the immune system. Associations between variants in the gene encoding the beta 2-adrenergic receptor (ADRB2) and autoimmune disorders such as rheumatoid arthritis (RA) have been demonstrated. We aimed to investigate ADRB2 variants for association with JIA.

METHODS

Genotypes and haplotypes of two ADRB2 variants (G16R and Q27E) were determined in 348 children with JIA and 448 healthy controls by direct molecular haplotyping using melting-curve analysis of a fluorescently labelled loci-spanning probe. Case-control analysis was performed to investigate whether ADRB2 variants were associated with JIA.

RESULTS

No association was found between JIA and alleles, genotypes, or haplotypes of ADRB2. Specifically, the haplotype that demonstrated a strong association with RA (R16/Q27) was not associated with JIA. None of the variants demonstrated association after stratification by JIA subtypes or gender.

CONCLUSIONS

Our results indicate that ADRB2 variants are not associated with JIA or any of the major JIA subtypes. These observations suggest that, although they share several clinical and pathological features, JIA and RA have unique genetic associations.

Association of two functional polymorphisms in the CCR5 gene with juvenile rheumatoid arthritis

Juvenile rheumatoid arthritis (JRA) is mediated by Th1-immune responses. In children with JRA, synovial T cells express high levels of the Th1-chemokine receptor CC chemokine receptor 5 (CCR5), which has been implicated in susceptibility to rheumatoid arthritis. To test the hypothesis that genetic variation in CCR5 is associated with susceptibility to JRA, we analyzed patterns of variation in the 5'cis-regulatory region of CCR5 in 124 multiplex families from a JRA-affected sibpair registry. After sequencing the upstream region of CCR5, variants were tested for association with JRA by transmission disequilibrium testing. A single nucleotide polymorphism, C-1835T, was significantly undertransmitted to children with early-onset JRA (P<0.01). C-1835T was genotyped in 424 additional simplex and multiplex families. CCR5-1835T allele was undertransmitted in the cohort of all probands with JRA (P<0.02), as well as in those with early-onset (P<0.01) or pauciarticular JRA (P<0.05). Another variant, a 32-bp deletion in the open reading frame of CCR5 (CCR5-Delta32) was also tested in approximately 700 simplex and multiplex families. CCR5-Delta32 was also significantly undertransmitted to probands with early-onset JRA (P<0.05). Both variants are in regions under natural selection, and result in functional consequences. Our results suggest these CCR5 variants are protective against early-onset JRA.

C-Myc-independent restoration of multiple phenotypes by two C-Myc target genes with overlapping functions

C-MYC, a transforming oncogene that is frequently overexpressed in many human cancers, regulates a variety of normal functions including cell cycle progression, apoptosis, and maintenance of cell size, morphology, and genomic integrity. Many target genes are modulated by c-Myc, and some can recapitulate a limited number of the above functions. Because most of these have been assessed in cells which also express endogenous c-Myc, however, it is not clear to what extent its proper regulation is also required. We show here that, in c-Myc nullizygous cells, two direct target genes, MT-MC1 and HMG-I, could each recapitulate multiple c-Myc phenotypes. Although these differ somewhat for the two genes, substantial overlap and cooperativity exist. The enforced expression of these two genes was also associated with the differential deregulation of some previously described c-Myc target genes, indicating the presence of a complex molecular circuitry. These observations argue that, despite the great diversity of gene regulation by c-Myc, many, although not all, of its functions can be phenocopied by a small subset of key downstream target genes. The approach described here should permit the identification of other target genes capable of further c-Myc-independent complementation.

The validity of the inter- and/or intrahemispheric deficit hypothesis as an explanation of the co-occurrence of motor and language impairments

From an initial cohort of 15 children, between the ages of 5 and 10 years, who had expressive oral language problems, 4 were shown in an earlier study to be both motor and language impaired. Two explanatory hypotheses were proposed to account for this communality: (a) cerebellar deficit; (b) inter- and/or intrahemispheric deficit. In order to explore the validity of the latter explanation, the same group of children, together with a matched control group, were required to carry out two sensory matching tests designed to tap inter- and intrahemispheric information processing abilities: hand-hand and foot-hand. The results, discussed in the light of Liederman's shielding model, provided more support for the hypothesis of an interhemispheric information processing problem from left to right rather than an intrahemispheric problem.

Direct evidence for a ruthenium(IV) oxo complex-mediated oxidation of a hydroxamic acid in the presence of phosphine oxide donors

Ruthenium(II) complexes can be used to oxidise N-Boc hydroxylamine the the presence of tert-butylhydroperoxide to the corresponding nitroso dienophile, which is trapped using cyclohexa-1,3-diene as the hetero-Diels-Alder adduct; direct evidence has been obtained for the intervention of a triphenylphosphine oxide-stabilised ruthenium(IV) oxocomplex as the catalytically active species.

Speed discrimination of stereoscopic (cyclopean) motion

This study investigated the degree to which speed of stereoscopic translational motion (i.e. moving binocular disparity information) can be discriminated in a display that minimizes position information. Observers viewed dynamic random-element stereograms depicting arrays of randomly positioned stereoscopic dots that moved bidirectionally. Two tasks were performed: a speed discrimination task and a displacement discrimination task. Across a range of conditions, speed could be discriminated under conditions in which displacement could not. Thus, speed of stereoscopic motion can be discriminated when position information is minimal. This result indicates that stereoscopic motion is sensed in a way that cannot be explained by feature tracking or by inferring the motion from memory of position and time.

Role of the site of protonation in the low-energy decompositions of gas-phase peptide ions

The dissociation of singly or multiply protonated peptide ions by using low-energy collisional activation (CA) is highly dependent on the sites of protonation. The presence of strongly basic amino acid residues in the peptide primary structure dictates the sites of protonation, which generates a precursor ion population that is largely homogeneous with respect to charge sites. Attempts to dissociate this type of precursor ion population by low-energy CA result in poor fragmentation via few pathways. The work described here represents a systematic investigation of the effects of charge heterogeneity in the precursor ion population of a series of model peptides in low-energy CA experiments. Incorporation of acidic residues in the peptide RLC*IFSC*FR (where C* indicates a cysteic acid residue), for example, balances the charge on the basic arginine residues, which enables the ionizing protons to reside on a number of less basic sites along the peptide backbone. This results in a precursor ion population that is heterogeneous with respect to charge site. Low-energy CA of these ions results in diverse and efficient fragmentation. Molecular modeling has been utilized to demonstrate that energetically preferred conformations incorporate an intraionic interaction between arginine and cysteic acid residues.

A regular pattern of two types of 100-residue motif in the sequence of titin

Titin is the largest polypeptide yet described (relative molecular mass approximately 3 x 10(6); refs 1, 2) and an abundant protein of striated muscle. Its molecules are string-like and in vivo span from the M to Z-lines. I-band regions of titin are thought to make elastic connections between the thick filament and the Z-line, thereby forming a third type of sarcomere filament. These would centre the A-band in the sarcomere and provide structural continuity in relaxed myofibrils. The A-band region of titin seems to be bound to the thick filament, where it has been proposed to act as a 'molecular ruler' regulating filament length and assembly. Here, we show that partial titin complementary DNAs encode a regular pattern of two types of 100-residue motif, each of which probably folds into a separate domain type. Such motifs are present in several evolutionarily divergent muscle proteins, all of which are likely to interact with myosin. One or both of the domain types is therefore likely to bind to myosin.

Does titin regulate the length of muscle thick filaments?

The protein titin has been localized by electron microscopy of myofibrils labelled with monoclonal antibodies. The data are consistent with individual titin molecules extending from near the M-line to beyond the ends of thick filaments, a distance of approximately 1 micron. In the A-band, titin appears to be bound to thick filaments, probably to the outside of the filament shaft. Molecules of titin in this configuration provided an obvious mechanism by which the length of thick filaments could be regulated accurately.

Purification and properties of native titin

A procedure has been developed for the extraction and purification of the massive myofibrillar protein titin without exposing it to denaturing conditions. The form of the molecule that has been isolated is soluble at high ionic strength and alkaline pH, but precipitates in low salt or at pH values below 7. Sedimentation velocity experiments indicate that titin is a highly asymmetric molecule with a sedimentation coefficient of 13.4 S. This asymmetry is confirmed by electron microscopy of rotary-shadowed specimens, which shows string-like structures of diameter 40 A and lengths up to 8000 A. Significant differences were observed depending on whether the electron microscope specimens were prepared by spraying or by layering of the titin onto a mica substrate; we tentatively attribute these differences to elasticity in the titin, revealed by the high shearing forces that accompany spraying. In accord with this, the circular dichroism spectrum of titin indicates that its secondary structure is largely random coil, a conformation characteristic of elastic proteins such as elastin. Negative staining of titin again shows long string-like structures, but these can now be seen to have an appearance similar to a string of beads, where the spacing between successive beads is about 40 A. Very similar beaded strings have been observed also associated with negatively stained separated native thick filaments; these are found running alongside the cross-bridge regions and in coils near the filament ends. Since the periodicity of the strings is similar to that of end-filaments, recently identified structures at the tips of thick filaments, it is likely that end-filaments are formed from titin. Titin comprises approximately 9% of the myofibrillar mass, which means that it is the third most abundant protein in muscle. The possible role of titin in forming elastic filaments within myofibrils is discussed.