Isoform-specific translational control is evolutionarily conserved in primates

Alternative splicing (AS) alters messenger RNA (mRNA) coding capacity, localization, stability, and translation. Here we use comparative transcriptomics to identify cis- acting elements coupling AS to translational control (AS-TC). We sequenced total cytosolic and polyribosome-associated mRNA from human, chimpanzee, and orangutan induced pluripotent stem cells (iPSCs), revealing thousands of transcripts with splicing differences between subcellular fractions. We found both conserved and species-specific polyribosome association patterns for orthologous splicing events. Intriguingly, alternative exons with similar polyribosome profiles between species have stronger sequence conservation than exons with lineage-specific ribosome association. These data suggest that sequence variation underlies differences in the polyribosome association. Accordingly, single nucleotide substitutions in luciferase reporters designed to model exons with divergent polyribosome profiles are sufficient to regulate translational efficiency. We used position specific weight matrices to interpret exons with species-specific polyribosome association profiles, finding that polymorphic sites frequently alter recognition motifs for trans- acting RNA binding proteins. Together, our results show that AS can regulate translation by remodeling the cis- regulatory landscape of mRNA isoforms.

Transcriptional repression by FEZF2 restricts alternative identities of cortical projection neurons

Projection neuron subtype identities in the cerebral cortex are established by expressing pan-cortical and subtype-specific effector genes that execute terminal differentiation programs bestowing neurons with a glutamatergic neuron phenotype and subtype-specific morphology, physiology, and axonal projections. Whether pan-cortical glutamatergic and subtype-specific characteristics are regulated by the same genes or controlled by distinct programs remains largely unknown. Here, we show that FEZF2 functions as a transcriptional repressor, and it regulates subtype-specific identities of both corticothalamic and subcerebral neurons by selectively repressing expression of genes inappropriate for each neuronal subtype. We report that TLE4, specifically expressed in layer 6 corticothalamic neurons, is recruited by FEZF2 to inhibit layer 5 subcerebral neuronal genes. Together with previous studies, our results indicate that a cortical glutamatergic identity is specified by multiple parallel pathways active in progenitor cells, whereas projection neuron subtype-specific identity is achieved through selectively repressing genes associated with alternate identities in differentiating neurons.

Safety and efficacy of subcutaneous alpha-tocopherol in healthy adult horses

Vitamin E is essential for neuromuscular function. The primary treatment, oral supplementation with natural ('RRR') α-tocopherol, is not effective in all horses. The objectives of this pilot study were to evaluate the safety and efficacy of a subcutaneously administered RRR-α-tocopherol preparation. Horses were randomly assigned in a cross-over design to initially receive RRR-α-tocopherol (5000 IU/450 kg of 600 IU/mL) subcutaneously (n = 3) or orally (n = 3) or were untreated sentinels (n = 2). Tissue reactions following injection in Phase I of the study necessitated adjustment of the preparation with reduction of the RRR-α-tocopherol concentration to 500 IU/mL in Phase 2. Following an 8-week washout period, horses received the reciprocal treatment route with the new preparation (5000 IU/450 kg of 500 IU/mL). Serum, CSF and muscle α-tocopherol concentrations were determined by high-performance liquid chromatography over a 14-day period during each phase. Serum and CSF α-tocopherol concentrations increased significantly postinjection only when the 500 IU/mL product was administered (P<0.0001). There was no significant difference in the muscle concentration of α-tocopherol following either treatment. All eight horses had marked tissue reaction to subcutaneous injection, regardless of product concentration. Whilst we have demonstrated that this route may be a useful alternative to oral supplementation, the marked tissue reaction makes use of such products limited at this time to only the most refractory of cases.

Blood and Cerebrospinal Fluid α-Tocopherol and Selenium Concentrations in Neonatal Foals with Neuroaxonal Dystrophy

Background

Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (NAD/EDM) is a neurodegenerative disorder affecting genetically predisposed foals maintained on α‐tocopherol (α‐TP)‐deficient diet.

Objective

Intramuscular α‐TP and selenium (Se) administration at 4 days of age would have no significant effect on serum or cerebrospinal fluid (CSF) α‐TP in healthy foals. Serum and CSF α‐TP, but not Se, would be significantly decreased in NAD/EDM‐affected foals during first year of life.

Animals

Fourteen Quarter horse foals; 10 healthy foals supplemented with 0.02 mL/kg injectable α‐TP and Se (n = 5) or saline (n = 5) at 4 days of age and 4 unsupplemented NAD/EDM‐affected foals.

Methods

Complete neurologic examinations were performed, blood and CSF were collected before (4 days of age) and after supplementation at 10, 30, 60, 120, 180, 240, and 360 days of age. Additional blood collections occurred at 90, 150, 210, and 300 days. At 540 days, NAD/EDM‐affected foals and 1 unsupplemented healthy foal were euthanized and necropsies performed.

Results

Significant decreases in blood, CSF α‐TP and Se found in the first year of life in all foals, with most significant changes in serum α‐TP from 4–150 days. Dam α‐TP and Se significantly influenced blood concentrations in foals. Injection of α‐TP and Se did not significantly increase CSF Se, blood or CSF α‐TP in healthy foals. NAD/EDM‐affected foals had significantly lower CSF α‐TP through 120 days.

Conclusions and Clinical Importance

Injection of α‐TP and Se at 4 days of age does not significantly increase blood or CSF α‐TP. Despite all 14 foals remaining deficient in α‐TP, only the 4 genetically predisposed foals developed NAD/EDM.

Juvenile coho salmon locomotion and mosaic muscle are modified by 3′,3′,5′-tri-iodo-l-thyronine (T(3))

Studies of maximum aerobic swimming performance in smolting juvenile salmonids indicate that these animals may be aerobically compromised during downstream migration. To test our hypothesis that hyperthyroid status contributes to decreased swimming performance through modification of muscle contractility in juvenile (112 mm mean total length) coho salmon (Oncorhynchus kisutch), we measured swimming performance and isolated muscle bundle contractility of fish implanted with 3′,3′,5′-tri-iodo-l-thyronine (T(3)) pellets, of fish implanted with sham pellets and of fish with no pellet implantation (control group). After 3 weeks (N=12-13), critical swimming speeds (maximum aerobic swimming speed or U(crit)) were measured. Muscle bundles (N=15-16) were dissected from the hypaxial musculature and stimulated to measure the force and velocity of an isometric twitch and tetani. T(3)-treated fish demonstrated visible morphological changes associated with smoltification. Mean values of U(crit) were significantly decreased and the prolonged contraction (tetani) and twitch rates of contraction, relaxation and maximum force were significantly increased by T(3) treatment compared with both the sham and control fish. Hematocrit, body mass and body length were not significantly affected by T(3) treatment. In conclusion, we suggest that the reported decrease in U(crit) during salmonid smoltification may be mediated by endogenous T(3)-induced contractile modification of mosaic muscle fibers.

The causes of failure of lumbar transpedicular spinal instrumentation and fusion: a prospective study

A prospective study was made of 101 patients who underwent transpedicular spinal instrumentation and fusion of the lumbar spine. All were reviewed by an independent observer. The objectives were to determine the causes of clinical failure and to recommend preventive measures. Forty-two primary and 59 revision operations were performed. The average age was 46 years and follow up 4 years. The variable screw placement and Cotrel-Dubousset systems were used. Posterior lumbar interbody fusion was carried out in 24 patients. The outcome was satisfactory after primary operations in 67% and after revisions in 46%. Nerve root injuries due to screw placement occurred in 4% (2% permanent and 2% transient). Instrumentation-induced foraminal stenosis developed in 2%. Proper surgical technique can avoid these complications. Predictive factors for failure are: abnormal psychology, symptomatic epidural fibrosis, inadequate decompression of lateral stenosis, surgical complications and the use of allografts.

The importance of the blood supply in the healing of tibial fractures

A clinical study of the effects of nonischemic arterial injuries to the leg on tibial fracture healing is presented. In addition, the literature published during the past 100 years describing the vascular supply to the tibia is reviewed, and the San Francisco General Hospital treatment protocol for difficult open tibial fractures is outlined. Based on the finding that the delayed and nonunion rate is three times higher when one of the three arteries of the leg is disrupted, a modification of the Gustilo fracture classification is proposed.

Delayed unions and nonunions of open tibial fractures. Correlation with arteriography results

To investigate the importance of arterial integrity in tibial fracture healing, the authors retrospectively assessed prognosis as a function of arterial injury in a large series of tibial fracture patients. The records of 114 patients who were treated for an open fracture of the tibia at a San Francisco hospital between 1981 and 1991 were selected for review; in each case, the injury had been caused by a blunt trauma, and arteriography had been performed to evaluate a suspected arterial injury in the ipsilateral extremity. Sixty-two patients had had a normal arteriogram and 52 had demonstrated occlusion of one or two of the three arteries that supply the foot. The group of patients who had demonstrated arterial occlusion had a significantly greater incidence of delayed union or nonunion (24 of 52 compared with ten of 62) and notably more cases of osteomyelitis (nine of 52 compared with four of 62); when the patients with osteomyelitis are excluded, the difference between the groups is still significant. This study is the first that indicates that patients with open fractures of the tibia who demonstrate arterial occlusion in their ipsilateral extremity may be more prone to delayed union or nonunion. More vigilant follow-up evaluation may therefore be warranted in such patients to better anticipate the need for exchange rodding or bone grafting.