Clinically relevant mouse models of Charcot-Marie-Tooth type 2S

Charcot-Marie-Tooth disease is an inherited peripheral neuropathy that is clinically and genetically heterogenous. Mutations in IGHMBP2, a ubiquitously expressed DNA/RNA helicase, have been shown to cause the infantile motor neuron disease spinal muscular atrophy with respiratory distress type 1 (SMARD1), and, more recently, juvenile-onset Charcot-Marie-Tooth disease type 2S (CMT2S). Using CRISPR-cas9 mutagenesis, we developed the first mouse models of CMT2S [p.Glu365del (E365del) and p.Tyr918Cys (Y918C)]. E365del is the first CMT2S mouse model to be discovered and Y918C is the first human CMT2S allele knock-in model. Phenotypic characterization of the homozygous models found progressive peripheral motor and sensory axonal degeneration. Neuromuscular and locomotor assays indicate that both E365del and Y918C mice have motor deficits, while neurobehavioral characterization of sensory function found that E365del mutants have mechanical allodynia. Analysis of femoral motor and sensory nerves identified axonal degeneration, which does not impact nerve conduction velocities in E365del mice, but it does so in the Y918C model. Based on these results, the E365del mutant mouse, and the human allele knock-in, Y918C, represent mouse models with the hallmark phenotypes of CMT2S, which will be critical for understanding the pathogenic mechanisms of IGHMBP2. These mice will complement existing Ighmbp2 alleles modeling SMARD1 to help understand the complex phenotypic and genotypic heterogeneity that is observed in patients with IGHMBP2 variants.

Author Correction: NEMF mutations that impair ribosome-associated quality control are associated with neuromuscular disease

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

NEMF mutations that impair ribosome-associated quality control are associated with neuromuscular disease

A hallmark of neurodegeneration is defective protein quality control. The E3 ligase Listerin (LTN1/Ltn1) acts in a specialized protein quality control pathway—Ribosome-associated Quality Control (RQC)—by mediating proteolytic targeting of incomplete polypeptides produced by ribosome stalling, and Ltn1 mutation leads to neurodegeneration in mice. Whether neurodegeneration results from defective RQC and whether defective RQC contributes to human disease have remained unknown. Here we show that three independently-generated mouse models with mutations in a different component of the RQC complex, NEMF/Rqc2, develop progressive motor neuron degeneration. Equivalent mutations in yeast Rqc2 selectively interfere with its ability to modify aberrant translation products with C-terminal tails which assist with RQC-mediated protein degradation, suggesting a pathomechanism. Finally, we identify NEMF mutations expected to interfere with function in patients from seven families presenting juvenile neuromuscular disease. These uncover NEMF’s role in translational homeostasis in the nervous system and implicate RQC dysfunction in causing neurodegeneration.

Defective protein quality control is a key feature of neurodegeneration. Here, the authors show that mutations in Nemf/NEMF, a component of the Ribosome-associated Quality Control complex, have a neurodegenerative effect in mice and may underlie neuromuscular disease in seven unrelated families.

Overlapping spectrums: The clinicogenetic commonalities between Charcot-Marie-Tooth and other neurodegenerative diseases

Charcot-Marie-Tooth (CMT) disease is a progressive and heterogeneous inherited peripheral neuropathy. A myriad of genetic factors have been identified that contribute to the degeneration of motor and sensory axons in a length-dependent manner. Emerging biological themes underlying disease include defects in axonal trafficking, dysfunction in RNA metabolism and protein homeostasis, as well deficits in the cellular stress response. Moreover, genetic contributions to CMT can have overlap with other neuropathies, motor neuron diseases (MNDs) and neurodegenerative disorders. Recent progress in understanding the molecular biology of CMT and overlapping syndromes aids in the search for necessary therapeutic targets.

Role of host-produced stimuli and learning in host selection behavior ofCotesia (=Apanteles) marginiventris (Cresson)

The study was conducted to determine how various factors, including learning, influence the host-selection behavior of the larval parasitoid Cotesia (=Apanteles)marginiventris (Cresson). Frass, silk, and feeding damage fromSpodoptera frugiperda (J.E. Smith) larvae elicited visits and antennal examinations by females of the parasitoid. Learning played a role in the effective response to these stimuli in that previous contact experience with hosts and/or chewed leaves, exuviae, frass, or hemolymph significantly enhanced the response of the parasitoid. Previous contact with host plants alone did not improve the responses. Experienced parasitoids were more active and spent less time at rest than inexperienced parasitoids. Previous experience was also found to be of significant importance in the ability of the parasitoid to discriminate between parasitized and unparasitized host larvae.

Clinical outcomes of aneurysmal subarachnoid hemorrhage patients treated with oral diltiazem and limited intensive care management

BACKGROUND

Aneurysmal subarachnoid hemorrhage (SAH) patients are frequently treated with prophylactic nimodipine and undergo invasive monitoring of blood pressure and volume status in an intensive care unit (ICU) setting to decrease the incidence of delayed ischemic neurological deficit (DIND) and improve functional outcomes. The goal of this study was to examine the incidence of DIND and poor functional outcomes in a consecutive series of SAH patients treated with a different regimen of prophylactic oral diltiazem and limited use of intensive care monitoring.

METHODS

The study involved a consecutive series of 123 aneurysmal SAH patients treated by the senior author who were admitted within 72 hours of hemorrhage and who never received nimodipine or nicardipine. Functional outcomes were graded using the Glasgow Outcome Scale (GOS).

RESULTS

Of the 123 patients identified, favorable outcomes (GOS 4 and 5) were achieved in 74.8%. The incidence of DIND was 19.5%. Hypertensive, hypervolemic, hemodilutional (HHH) therapy was used in 10 patients (8.1%) and no patients were treated for DIND by endovascular means. Seven patients (5.7%) had a poor functional outcome or death because of DIND and two of these were related to complications of HHH therapy. These results were compared to contemporary series of SAH patients managed with other treatment protocols.

CONCLUSIONS

Functional outcomes of patients treated with a regimen of oral diltiazem, limited use of ICU monitoring and HHH therapy for DIND compare favorably with other contemporary series of SAH patients.

Massachusetts Risk Management Survey (MaRMS) of teaching hospital physicians

OBJECTIVE

To assess and compare the risk management knowledge of physicians from Massachusetts teaching hospitals.

DESIGN

A survey.

SETTING

Participating Massachusetts teaching hospitals.

PARTICIPANTS

639 of some 2,000 staff physicians of participant hospitals who were sent surveys. An additional 174 postgraduate year 1 (PGY1) and PGY3 house officers also completed the survey.

MAIN OUTCOME MEASURES

Percent of questions answered correctly, and comparisons between staff physicians and house officers.

RESULTS

Staff physicians scored higher (87%) than PGY1s and PGY3s combined (81%), P<0.001. Scores among staff physicians did not differ according to field of medicine, age, proportion of time spent in clinical practice, or years in practice. PGY3s did not score significantly higher than PGY1s (82% vs. 80%). Some 40% of physicians said they ordered more tests than necessary because of malpractice worries; they indicated 72% of their colleagues do so as well. Physicians in obstetrics-gynecology and emergency medicine were more likely to respond yes to this question than physicians in other fields of medicine (P<0.001), as were physicians who had been defendants in a malpractice suit (88 P=0.013).

CONCLUSIONS

Surveyed staff physicians have an adequate risk management knowledge. Training directors should encourage house officers to attend risk management programs to improve their knowledge. Physicians might overestimate the amount spent on defense medicine based on their perceptions of other physicians.

The use of omeprazole for resistant oesophagitis in children

Following failure of conventional therapy for reflux oesophagitis, 15 children were treated with omeprazole 20 mg daily for a period of up to three months initially. Treatment resulted in a marked symptomatic improvement as measured by incidence of pain, vomiting, dysphagia and haematemesis. Four children failed treatment and required fundoplication. No complications from the use of omeprazole were recorded and some children have continued long-term treatment.