Exploring the utility of whole‐exome sequencing as a diagnostic tool in a child with atypical episodic muscle weakness

The advent of whole‐exome next‐generation sequencing (WES) has been pivotal for the molecular characterization of Mendelian disease; however, the clinical applicability of WES has remained relatively unexplored. We describe our exploration of WES as a diagnostic tool in a 3½‐year old female patient with a 2‐year history of episodic muscle weakness and paroxysmal dystonia who presented following a previous extensive but unrevealing diagnostic work‐up. WES was performed on the proband and her two parents. Parental exome data was used to filter potential de novo genomic events in the proband and suspected variants were confirmed using di‐deoxy sequencing. WES revealed a de novo non‐synonymous mutation in exon 21 of the calcium channel gene CACNA1S that has been previously reported in a single patient as a rare cause of atypical hypokalemic periodic paralysis. This was unexpected, as the proband's original differential diagnosis had included hypokalemic periodic paralysis, but clinical and laboratory features were equivocal, and standard clinical molecular testing for hypokalemic periodic paralysis and related disorders was negative. This report highlights the potential diagnostic utility of WES in clinical practice, with implications for the approach to similar diagnostic dilemmas in the future.     

Transfer of patients with acute myocardial infarction for primary or acute angioplasty from hospitals without the facilities to perform angioplasty. Results from the pooled data of the Maximal Individual Therapy in Acute Myocardial Infarction (MITRA) Registry and the Myocardial Infarction Registry (MIR)

In patients with acute myocardial infarction (AMI) admitted at hospitals without angioplasty facilities there are some subgroups of patients which seem to profit from a transfer to primary or acute angioplasty. However, current clinical practice at such hospitals is unknown. We analyzed the pooled data of the German acute myocardial infarction registries MITRA and the MIR. Angioplasty was not available at 221/271 hospitals (81.5%). Out of 14,487 patients with acute myocardial infarction admitted to these hospitals, 50.1% (7,259/14,487) received thrombolysis at the initial hospital and 3.6% (523/14,487) were transferred. Out of the transferred patients, 55.3% (289/523) were treated with primary angioplasty and 44.7% (234/523) received a combination of thrombolysis and angioplasty. The proportion of transferred patients increased from 1.1% in 1994 to 5.5% in 1998 (p for trend = 0.001). One hundred and four hospitals (47.1%) never transferred patients. Patients transferred for primary angioplasty (289 patients) were compared to patients treated with thrombolysis at the initial hospitals (7,259 patients). Multivariate analysis showed the following independent predictors for transfer of patients for primary angioplasty: contraindications for thrombolysis (OR = 17.9), a non-diagnostic first ECG (OR = 4.0), pre-hospital delay > 6 hours (OR = 2.5), unknown symptom onset of the acute myocardial infarction (OR = 2.0) and anterior wall acute myocardial infarction (OR = 1.6). Heart failure at admission was the only independent predictor not to transfer patients (OR = 0.40). In Germany only 47.1% of hospitals without angioplasty facilities transfer patients with acute myocardial infarction to primary or acute angioplasty. The proportion of transferred patients increased from 1.1% in 1994 to 5.5% in 1998. Contraindications for thrombolysis were the strongest predictor to transfer patients to primary angioplasty.     

Primary angioplasty versus no reperfusion therapy in patients with acute myocardial infarction and a pre-hospital delay of > 12-24 hours: results from the pooled data of the maximal individual therapy in acute myocardial infarction (MITRA) registry and the myocardial infarction registry (MIR)

OBJECTIVE: In patients with acute myocardial infarction (AMI), treatment with thrombolysis is superior to no reperfusion therapy only up to 12 hours after the onset of symptoms. There are no data addressing whether this time limit is also justified for treatment with primary angioplasty. DESIGN: The pooled data of two German ST-segment elevation AMI registries, the Maximal Individual Therapy in Acute Myocardial Infarction (MITRA) study and the Myocardial Infarction Registry (MIR), were analyzed. PATIENTS: Out of 22,749 patients, eight hundred and forty-eight with a pre-hospital delay of > 12 hours and < or = 24 hours were treated with either primary angioplasty (94/848; 11.1%) or no reperfusion therapy (754/848; 88.9%). RESULTS: Patients treated with primary angioplasty were 10 years younger (59 years versus 69 years; p = 0.001), more often male [72.3% versus 59.9%; odds ratio (OR) = 0.57; 95% confidence interval (CI) = 0.36-0.92] and less likely to be diabetics (17% versus 27.2%; OR = 0.55; 95% CI = 0.31-0.97). Hospital mortality was 8.5% in patients treated with primary angioplasty compared to 17.1% in patients with no reperfusion therapy (OR = 0.45; 95% CI = 0.21-0.95; p = 0.033) and the combined endpoint (death, reinfarction or stroke) occurred significantly less often (11.7% versus 20.3%; OR = 0.52; 95% CI =0.27-1; p = 0.045). However, multiple logistic regression showed only a non-significant trend for lower mortality (OR = 0.54; 95% CI =0.20-1.23) and the combined endpoint (OR = 0.65; 95% CI = 0.29-1.31) in patients treated with primary angioplasty. CONCLUSIONS: These data show the possibility of a benefit of primary angioplasty over conservative treatment in patients with pre-hospital delays of > 12 up to 24 hours, although multiple logistic regression analysis failed to find significant differences between treatments. This might be due to inadequate study power or a selection bias. These findings encourage further investigation of this subject.     

From the Cover: A new tubulin-binding site and pharmacophore for microtubule-destabilizing anticancer drugs

The recent success of antibody–drug conjugates (ADCs) in the treatment of cancer has led to a revived interest in microtubule-destabilizing agents. Here, we determined the high-resolution crystal structure of the complex between tubulin and maytansine, which is part of an ADC that is approved by the US Food and Drug Administration (FDA) for the treatment of advanced breast cancer. We found that the drug binds to a site on β-tubulin that is distinct from the vinca domain and that blocks the formation of longitudinal tubulin interactions in microtubules. We also solved crystal structures of tubulin in complex with both a variant of rhizoxin and the phase 1 drug PM060184. Consistent with biochemical and mutagenesis data, we found that the two compounds bound to the same site as maytansine and that the structures revealed a common pharmacophore for the three ligands. Our results delineate a distinct molecular mechanism of action for the inhibition of microtubule assembly by clinically relevant agents. They further provide a structural basis for the rational design of potent microtubule-destabilizing agents, thus opening opportunities for the development of next-generation ADCs for the treatment of cancer.Microtubule-targeting agents such as the taxanes and the vinca alkaloids represent a successful class of anticancer drugs (1). Vinblastine, for example, is a microtubule-destabilizing agent (MDA) that is widely used in combination therapy for the treatment of childhood and adult malignancies (2). The broad clinical application of MDAs, however, is hampered by their severe adverse effects (3). This problem has been very recently addressed by the use of antibody–drug conjugate (ADC) approaches, which have revived interest in the development of highly potent MDAs for therapeutic use (4–6).For several important MDAs, the molecular mechanism of action on tubulin and microtubules has so far remained elusive. Rhizoxin, for example, is a potent MDA that has been investigated in phase 2 clinical trials, but for reasons poorly understood, it has demonstrated only very limited clinical efficacy (7). At the molecular level, it is well established that rhizoxin interferes with the binding of vinblastine to tubulin; however, the exact location of its binding site has been a matter of debate (8–10). Interestingly, biochemical and mutagenesis data suggest that the structurally unrelated MDA maytansine (9, 11), which is part of an ADC that was recently approved by the FDA for the treatment of advanced breast cancer (11, 12), and the phase 1 drug PM060184 (13, 14) (Fig. 1A) share a common tubulin-binding site with rhizoxin (9, 13, 14). These two latter drugs have also been reported to interfere with the binding of vinblastine; however, as for rhizoxin, the exact binding sites and modes of action of maytansine and PM060184 have not been elucidated (9, 14–16).Open in a separate windowFig. 1.Structure of the tubulin–rhizoxin F complex. (A) Chemical structures of rhizoxin F, maytansine, and PM060184. (B) Overall view of the T₂R-TTL–rhizoxin F complex. Tubulin (gray), RB3 (light green), and TTL (violet) are shown in ribbon representation; the MDA rhizoxin F (orange) and GDP (cyan) are depicted in spheres representation. As a reference, the vinblastine structure (yellow, PDB ID no. 1Z2B) is superimposed onto the T₂R complex. (C) Overall view of the tubulin–rhizoxin F interaction in two different orientations. The tubulin dimer with bound ligand (α-tubulin-2 and β-tubulin-2 of the T₂R-TTL–rhizoxin F complex) is shown in surface representation. The vinblastine structure is superimposed onto the β-tubulin chain to highlight the distinct binding site of rhizoxin F. All ligands are in sphere representation and are colored in orange (rhizoxin F), cyan (GDP), and yellow (vinblastine). (D) Close-up view of the interaction observed between rhizoxin F (orange sticks) and β-tubulin (gray ribbon). Interacting residues of β-tubulin are shown in stick representation and are labeled.To establish the exact tubulin-binding site of rhizoxin, maytansine, and PM060184 and to clarify their specific interactions with the protein, we have investigated the structures of the corresponding ligand–tubulin complexes by X-ray crystallography. Our data reveal a new tubulin-binding site and pharmacophore for small molecules, and binding to this site is associated with a distinct molecular mechanism for the inhibition of microtubule formation.     

On the origin of long-range correlations in texts

The complexity of human interactions with social and natural phenomena is mirrored in the way we describe our experiences through natural language. In order to retain and convey such a high dimensional information, the statistical properties of our linguistic output has to be highly correlated in time. An example are the robust observations, still largely not understood, of correlations on arbitrary long scales in literary texts. In this paper we explain how long-range correlations flow from highly structured linguistic levels down to the building blocks of a text (words, letters, etc..). By combining calculations and data analysis we show that correlations take form of a bursty sequence of events once we approach the semantically relevant topics of the text. The mechanisms we identify are fairly general and can be equally applied to other hierarchical settings.     

The functions of the orbitofrontal cortex

Parkinson's disease is commonly accompanied by cognitive issues that limit participation in activities of daily living. Unfortunately, most current treatment paradigms and pharmacotherapeutics fail to address the cognitive impairment demonstrated in this population. Mounting evidence in healthy older adults suggests that aerobic exercise may improve cognitive function. This article describes a patient with Parkinson's disease prescribed 8 weeks of aerobic exercise. Despite very high performance at baseline, the participant improved on several cognitive measures post exercise. The results of this investigation mimic the research in healthy older adults. We therefore suggest that future large scale randomized trials are warranted to evaluate the efficacy of aerobic exercise for ameliorating declines in cognitive performance in persons with PD.     

Effects of regularity on the processing of sound omission in a tone sequence in musicians and non‐musicians

Numerous studies have reported that perceptual grouping affects the pre‐attentive processing of sound omission in a sequence of tones. However, it remains unclear whether or not the perceptual grouping and musical experience affect the attentive processing of sound omission. To this end, we created a sequence of loud (L) and soft (S) tones grouped as ‘LLSLLS…’ and a random sequence of the L and S tones. The omission of the L tones was inserted pseudo‐randomly in the random sequence, and there were two positions at which it was inserted. For within‐group omission, the omission was after the first L tone within the ‘LLS’ pattern. For between‐group omission, the omission was inserted between the patterns. The brain response to the omission in musicians and non‐musicians was measured using magnetoencephalography. During the magnetoencephalography measurement, the subjects' performance in a task to detect the omission was faster in the random sequence than in the group sequence. Source analysis showed that the omission in the random sequence caused greater activity than that in the group sequence. The increase was found in the right inferior parietal lobe in musicians, whereas it was found in the left superior temporal gyrus in non‐musicians. These results suggest that the attentive processing of perceptual grouping might implicate the left superior temporal gyrus or right inferior parietal lobe, depending on musical experience.