The Mediator kinase module enhances polymerase activity to regulate transcriptional memory after heat stress in Arabidopsis

Plants are often exposed to recurring adverse environmental conditions in the wild. Acclimation to high temperatures entails transcriptional responses, which prime plants to better withstand subsequent stress events. Heat stress (HS)-induced transcriptional memory results in more efficient re-induction of transcription upon recurrence of heat stress. Here, we identified CDK8 and MED12, two subunits of the kinase module of the transcription co-regulator complex, Mediator, as promoters of heat stress memory and associated histone modifications in Arabidopsis. CDK8 is recruited to heat-stress memory genes by HEAT SHOCK TRANSCRIPTION FACTOR A2 (HSFA2). Like HSFA2, CDK8 is largely dispensable for the initial gene induction upon HS, and its function in transcriptional memory is thus independent of primary gene activation. In addition to the promoter and transcriptional start region of target genes, CDK8 also binds their 3'-region, where it may promote elongation, termination, or rapid re-initiation of RNA polymerase II (Pol II) complexes during transcriptional memory bursts. Our work presents a complex role for the Mediator kinase module during transcriptional memory in multicellular eukaryotes, through interactions with transcription factors, chromatin modifications, and promotion of Pol II efficiency.

Genomic and epigenomic determinants of heat stress-induced transcriptional memory in Arabidopsis

BACKGROUND

Transcriptional regulation is a key aspect of environmental stress responses. Heat stress induces transcriptional memory, i.e., sustained induction or enhanced re-induction of transcription, that allows plants to respond more efficiently to a recurrent HS. In light of more frequent temperature extremes due to climate change, improving heat tolerance in crop plants is an important breeding goal. However, not all heat stress-inducible genes show transcriptional memory, and it is unclear what distinguishes memory from non-memory genes. To address this issue and understand the genome and epigenome architecture of transcriptional memory after heat stress, we identify the global target genes of two key memory heat shock transcription factors, HSFA2 and HSFA3, using time course ChIP-seq.

RESULTS

HSFA2 and HSFA3 show near identical binding patterns. In vitro and in vivo binding strength is highly correlated, indicating the importance of DNA sequence elements. In particular, genes with transcriptional memory are strongly enriched for a tripartite heat shock element, and are hallmarked by several features: low expression levels in the absence of heat stress, accessible chromatin environment, and heat stress-induced enrichment of H3K4 trimethylation. These results are confirmed by an orthogonal transcriptomic data set using both de novo clustering and an established definition of memory genes.

CONCLUSIONS

Our findings provide an integrated view of HSF-dependent transcriptional memory and shed light on its sequence and chromatin determinants, enabling the prediction and engineering of genes with transcriptional memory behavior.

Design and implementation of electron diverters for lobster eye space-based X-ray optics

Micropore optics have recently been implemented in a lobster eye geometry as a compact X-ray telescope. Fields generated by rare-earth magnets are used to reduce the flux of energetic electrons incident upon the focal plane detector in such a setup. We present the design and implementation of the electron diverters for X-ray telescopes of two upcoming missions: the microchannel X-ray telescope onboard the space-based multiband astronomical variable objects monitor and the soft X-ray instrument onboard the solar wind magnetosphere ionosphere link explorer. Electron diverters must be configured to conform to stringent limits on their total magnetic dipole moment and be compensated for any net moment arising from manufacturing errors. The two missions have differing designs, which are presented and evaluated in terms of the fractions of electrons reaching the detector, as determined by relativistic calculations of electron trajectories. The differential flux of electrons to the detector is calculated, and the integrated electron background is determined for both designs.

The role of retrograde signals during plant stress responses

Chloroplast and mitochondria not only provide the energy to the plant cell but due to the sensitivity of organellar processes to perturbations caused by abiotic stress, they are also key cellular sensors of environmental fluctuations. Abiotic stresses result in reduced photosynthetic efficiency and thereby reduced energy supply for cellular processes. Thus, in order to acclimate to stress, plants must re-program gene expression and cellular metabolism to divert energy from growth and developmental processes to stress responses. To restore cellular energy homeostasis following exposure to stress, the activities of the organelles must be tightly co-ordinated with the transcriptional re-programming in the nucleus. Thus, communication between the organelles and the nucleus, so-called retrograde signalling, is essential to direct the energy use correctly during stress exposure. Stress-triggered retrograde signals are mediated by reactive oxygen species and metabolites including β-cyclocitral, MEcPP (2-C-methyl-d-erythritol 2,4-cyclodiphosphate), PAP (3'-phosphoadenosine 5'-phosphate), and intermediates of the tetrapyrrole biosynthesis pathway. However, for the plant cell to respond optimally to environmental stress, these stress-triggered retrograde signalling pathways must be integrated with the cytosolic stress signalling network. We hypothesize that the Mediator transcriptional co-activator complex may play a key role as a regulatory hub in the nucleus, integrating the complex stress signalling networks originating in different cellular compartments.

Redox regulation of PEP activity during seedling establishment in Arabidopsis thaliana

Activation of the plastid-encoded RNA polymerase is tightly controlled and involves a network of phosphorylation and, as yet unidentified, thiol-mediated events. Here, we characterize PLASTID REDOX INSENSITIVE2, a redox-regulated protein required for full PEP-driven transcription. PRIN2 dimers can be reduced into the active monomeric form by thioredoxins through reduction of a disulfide bond. Exposure to light increases the ratio between the monomeric and dimeric forms of PRIN2. Complementation of prin2-2 with different PRIN2 protein variants demonstrates that the monomer is required for light-activated PEP-dependent transcription and that expression of the nuclear-encoded photosynthesis genes is linked to the activity of PEP. Activation of PEP during chloroplast development likely is the source of a retrograde signal that promotes nuclear LHCB expression. Thus, regulation of PRIN2 is the thiol-mediated mechanism required for full PEP activity, with PRIN2 monomerization via reduction by TRXs providing a mechanistic link between photosynthetic electron transport and activation of photosynthetic gene expression.

The plastid-encoded RNA polymerase PEP is regulated according to plastid redox state. Here, the authors show that the redox-regulated PRIN2 protein is reduced to monomeric form in a thiol-dependent manner in response to light and that PRIN2 monomers are required for PEP activity and retrograde signaling.

Identifying the barriers and enablers in the implementation of the New Zealand and Australian Antenatal Corticosteroid Clinical Practice Guidelines

Background

The ineffective implementation of evidence based practice guidelines can mean that the best health outcomes are not achieved. This study examined the barriers and enablers to the uptake and implementation of the new bi-national (Australia and New Zealand) antenatal corticosteroid clinical practice guidelines among health professionals, using the Theoretical Domains Framework.

Methods

Semi-structured interviews or online questionnaires were conducted across four health professional groups and three district health boards in Auckland, New Zealand. The questions were constructed to reflect the 14 behavioural domains from the Theoretical Domains Framework. Relevant domains were identified by the presence of conflicting beliefs within a domain; the frequency of beliefs; and the likely strength of the impact of a belief on the behaviour using thematic analysis. The influence of health professional group and organisation on the different barriers and enablers identified were explored.

Results

Seventy-three health professionals completed either a semi-structured interview (n = 35) or on-line questionnaire (n = 38). Seven behavioural domains were identified as overarching enablers: belief about consequences; knowledge; social influences; environmental context and resource; belief about capabilities; social professional role and identity; and behavioural regulation. Five behavioural domains were identified as overarching barriers: environmental context and resources; knowledge; social influences; belief about consequences; and social professional role and identity. Differences in beliefs between individual health professional groups were identified within the domains: belief about consequences; social professional role and identity; and emotion. Organisational differences were identified within the domains: belief about consequences; social influences; and belief about capabilities.

Conclusion

This study has identified some of the enablers and barriers to implementation of the New Zealand and Australian Antenatal Corticosteroid Clinical Practice Guidelines using the validated Theoretical Domains Framework, as perceived by health professionals. We have identified differences between individual health professional groups and organisations. The identification of these behavioural determinants can be used to enhance an implementation strategy, assist in the design of interventions to achieve improved implementation and facilitate process evaluations to understand why or how change interventions are effective.

Electronic supplementary material

The online version of this article (doi:10.1186/s12913-016-1858-8) contains supplementary material, which is available to authorized users.

Consumers attitudes and beliefs towards the receipt of antenatal corticosteroids and use of clinical practice guidelines

BACKGROUND

Active participation of consumers in health care decision making, policy and clinical research is increasingly encouraged by governments, influential bodies and funders. Identifying the best way to achieve this is difficult due to the paucity of evidence. Consumers have mixed feelings towards clinical practice guidelines (CPG) demonstrating scepticism towards their purpose and applicability to their needs. There is no information pertaining to consumers' views and attitudes on the receipt of antenatal corticosteroids (ACS). The aim of this study was to examine the barriers and enablers to receiving ACS and use of CPG amongst consumers.

METHODS

Consumers were recruited from neonatal units across three district health boards (DHBs) in Auckland, New Zealand. Participants completed a semi-structured interview or questionnaire. The questions posed and analyses were informed by the Theoretical Domains Framework (TDF). Barriers and enablers were identified by the presence of conflicting beliefs within a domain; the frequency of beliefs; and the likely strength of the impact of a belief on use of CPG and receipt of ACS.

RESULTS

Twenty four consumers participated in the study. Six domains were identified as barriers to receipt of ACS and use of CPG. Key barriers to receipt of ACS included: difficulty retaining information conveyed, requiring further information in a variety of formats, and time constraints faced by consumers and health professionals in the provision and understanding of information to facilitate decision making. Barriers to use of CPG included: uncertainty about applicability of guideline use among consumers and scepticism about health professionals adhering too rigidly to guidelines. Enablers to receipt of ACS included: optimism toward ACS use, a strong knowledge of why ACS were administered, improved resilience in their pregnancy and confidence in their decision making following receipt of information about ACS. Enablers to use of CPG included: validation and standardisation of decision making among health professionals providing care and facilitating the best care for women and their babies.

CONCLUSIONS

Key barriers and enablers exist among consumers regarding receipt of ACS and use of CPG. These need to be addressed or modified in any intervention strategy to facilitate implementation of the ACS CPG.

Note: a simple thermal gradient annealing unit for the treatment of thin films

A gradient annealing cell has been developed for the high-throughput study of thermal annealing effects on thin-film libraries in different environments. The inexpensive gradient annealing unit permits temperature gradients as large as 28 °C∕mm and can accommodate samples ranging in length from 13 mm to 51 mm. The system was validated by investigating the effects of annealing temperature on the crystallinity, resistivity, and transparency of tin-doped indium oxide deposited on a glass substrate by magnetron sputtering. The unit developed in this work will permit the rapid optimization of materials properties such as crystallinity, homogeneity, and conductivity across a variety of applications.

Differential effects of antiepileptic drugs on neonatal outcomes

Offspring of women with epilepsy (WWE) on AEDs are at increased risks for major congenital malformations and reduced cognition. They may be at risk for other adverse neonatal outcomes. Women with epilepsy on carbamazepine (CBZ), lamotrigine (LTG), phenytoin (PHT), or valproate (VPA) monotherapy were enrolled in a prospective, observational, multicenter study of the neurodevelopmental effects of AEDs. The odds ratio for small for gestational age (SGA) was higher for VPA vs. PHT, VPA vs. LTG, and CBZ vs. PHT. Microcephaly rates were elevated to 12% for all newborns and at 12 months old, but normalized by age 24 months. Reduced Apgar scores occurred more frequently in the VPA and PHT groups at 1 min, but scores were near normal in all groups at 5 min. This study demonstrates increased risks for being born SGA in the VPA and CBZ groups, and transiently reduced Apgar scores in the VPA and PHT groups. Differential risks among the AEDs can help inform decisions about AED selection for women during childbearing years.

An e-Research approach to Web-scale music analysis

The growing quantity of digital recorded music available in large-scale resources such as the Internet archive provides an important new resource for musical analysis. An e-Research approach has been adopted in order to create a very substantive web-accessible corpus of musical analyses in a common framework for use by music scholars, students and beyond, and to establish a methodology and tooling that will enable others to add to the resource in the future. The enabling infrastructure brings together scientific workflow and Semantic Web technologies with a set of algorithms and tools for extracting features from recorded music. It has been used to deliver a prototype system, described here, that demonstrates the utility of LINKED DATA for enhancing the curation of collections of music signal data for analysis and publishing results that can be simply and readily correlated to these and other sources. This paper describes the motivation, infrastructure design and the proof-of-concept case study and reflects on emerging e-Research practice as researchers embrace the scale of the Web.

Occupational status, work-site cessation programs and policies and menthol smoking on quitting behaviors of US smokers

AIM

This exploratory study sought to examine the relationships among occupational status, menthol smoking preference and employer-sponsored smoking cessation programs and policies on quitting behaviors.

DESIGN

Data for this cross-sectional study were obtained from the 2006 Tobacco Use Supplement to the Current Population Survey (TUS CPS), a large national survey representative of the civilian population, containing approximately 240,000 respondents. The total sample for the current study was 30,176.

MEASUREMENTS

The TUS CPS regularly collects data on cigarette prevalence, quitting behaviors, smoking history and consumption patterns. We performed a logistic regression with 'life-time quitting smoking for 1 day or longer because they were trying to quit' as outcome variable. Independent variables included type of occupation, employer-sponsored cessation programs and policies and menthol status.

FINDINGS

When controlling for occupational status and work-place policies, there were no differences for menthol versus non-menthol smokers on quitting behaviors [odds ratio (OR) = 0.98; 95% confidence interval (CI) = 0.83, 1.15]. Service workers were less likely to quit compared with white-collar workers (OR = 0.80; 95% CI = 0.69, 0.94), and those with no employer-sponsored cessation program were less likely to quit (OR = 0.70; 95% CI = 0.60, 0.83). White-collar workers, compared with blue-collar and service workers, were more likely to have a smoking policy in the work area (93% versus 86% versus 88%, respectively).

CONCLUSIONS

When occupational status and work-place smoking policies are controlled for, smokers of menthol cigarettes in the United States appear to have similar self-reported life-time rates of attempts to stop smoking to non-menthol smokers.

Health profile differences for menthol and non-menthol smokers: findings from the National Health Interview Survey

AIMS

Although the adverse effects of smoking are well known, limited information exists about the overall health profiles of menthol smokers when compared to their non-menthol smoking counterparts. Using a well-known nationally representative survey, this study examines differences between self-reported health characteristics for menthol and non-menthol smokers.

DESIGN

Cross-sectional data from the 2005 National Health Interview Survey and its cancer control supplement were used to analyze responses for current and former smokers (n = 12,004) independently. All analyses were conducted using SAS version 9.2 and SAS callable SUDAAN version 9.0.3. Multiple logistic regression analysis was used to model menthol smoking.

FINDINGS

After controlling for sex, age and race, we found that in current smokers the mean number of cigarettes smoked per day is significantly lower for menthol smokers when compared to non-menthol smokers [odds ratio (OR): 0.99; 95% confidence interval (CI): 0.98, 1.00]. Also, we found that former menthol smokers had higher body mass indices (BMIs) (OR: 1.01; 95% CI: 1.00, 1.02) and were more likely to have visited the emergency room due to asthma (OR: 2.30, 95% CI: 1.04, 5.09).

CONCLUSIONS

Overall, current menthol and non-menthol smokers have similar health profiles. However, menthol smokers reported smoking fewer cigarettes per day than their non-menthol counterparts. While these findings are supportive of other published data, future studies may need to tease out the health-related significance of smoking fewer menthol cigarettes per day but having similar health outcomes to those who smoke more non-menthol cigarettes per day. Additionally, our findings suggest that there may be some differences between the former menthol and non-menthol smoker.

Time-dependent observer errors in pulmonary nodule detection

The work was carried out to investigate differences in visual search characteristics between groups of observers with different levels of experience in the task of pulmonary nodule detection in chest radiology and we report here on these differences in respect of time related decisions. Volunteer observers were divided into three groups depending on their level of expertise. There were eight radiologists, eight radiographers and eight novices. Their task was to detect pulmonary nodules in a test bank of 120 digitized posteroanterior (PA) chest radiographs. Five of the eight radiographers were tested twice: once before and once after a 6-month training programme in interpretation of the adult chest radiograph. During each test session the observers' eye movements were tracked. Data on the observers' decisions through Alternate Free Response Operating Characteristic (AFROC) methodology were correlated to their eye-movement and fixation patterns. True negative decisions from all observers were associated with shorter fixation times than false negative decisions. No correct negative decisions were made after fixations exceeding 3 s.

Parental views about services for children attending schools for the emotionally and behaviourally disturbed (EBD): a qualitative analysis

AIM

This study examines the views of parents of children attending schools for the emotionally and behaviourally disturbed (EBD). The study aims to gain an understanding of the journey through the educational system taken by these children and to explore their families' experience of services along the way.

METHODS

Thirty parents of 25 children attending primary and secondary EBD schools in three South London boroughs took part in focus group discussions. Parents were asked about their experiences of services, including educational, health and social services, as well as how they thought services should be improved.

RESULTS

Qualitative analysis identified a complex web of individual, professional and organizational factors which contributed to social exclusion of children with EBD problems and their families. These factors included children receiving inadequate education because of long periods of exclusion or inappropriate placements whilst waiting for a statement of special educational needs. Parents also felt personally socially excluded because of lack of childcare provision out of school hours. Many parents felt that their children did not fit into services and were constantly being passed on to other professionals. The analysis identified aspects of services that promote social inclusion and provide support to families, including acceptance of children into EBD schools, help from voluntary organizations and support from other parents with children with EBD problems. Parents particularly stressed the value of working in collaboration with professionals to achieve shared goals.

CONCLUSION

EBD schools provide a valuable resource for parents. However parents often lack emotional and practical support in coping with their children's complex needs. Agencies need to improve communication and joint working to provide effective services for these families.

Respiratory flutter syndrome: an underrecognized cause of respiratory failure in neonates

We report the clinical and respiratory data of three neonates with flutter of the diaphragm and intercostal muscles, presenting soon after birth with respiratory failure. The breathing pattern was dirhythmic with superimposed frequencies, one regular and slow (60/min) representing the underlying respiratory rate, the other fast (> 300/min) and limited to inspiration. Nasal continuous positive airway pressure immediately normalized the breathing pattern in one infant, and improved ventilation in the two others. Pharmacologic therapy with chlorpromazine terminated the respiratory flutter and permitted weaning of ventilatory support within a few hours. Coexistent dysphagia suggested a disorder of brainstem function, although the children were otherwise developmentally normal at 8, 10, and 26 mo old. Laryngomalacia and gastroesophageal reflux were also present. We propose that the occurrence of respiratory flutter, dysphagia, laryngomalacia, and gastroesophageal reflux in a neonate constitutes a distinct clinical entity, termed the "respiratory flutter syndrome." The diagnosis of three infants with this presentation during an 18-mo period suggests that this may be a more frequent cause of respiratory failure in newborns than previously recognized.

The effect of imaging modality on patient management in the evaluation of pulmonary thromboembolism

A retrospective medical record review was performed to study the differences in clinical risk profiles and the relationships between test results versus management for suspected pulmonary thromboembolism (TE) in patients undergoing either radionuclide ventilation perfusion (V/Q) scans or pulmonary computed tomographic angiography (CTA), as the initial test. Data of 138 consecutive V/Q patients were compared with that of 149 consecutive CTA patients during equivalent 6-month intervals before and after the introduction of CTA. Information on risk factors, signs and symptoms, all diagnostic test results, and the relationships between the test results and ultimate physician management were collected and analyzed. V/Q results predicted physician management in all patients with high probability scans and 91% with normal to low probability scans. There were 35 patients with indeterminate V/Q scans--43% of these patients were managed without any other diagnostic test. CTA results predicted management in all patients with positive studies and 99% of patients with negative studies. In contrast to the V/Q cohort, only seven CTA studies were inconclusive--additional diagnostic tests determined management in all but one case. Compared with V/Q, CTA has fewer indeterminate results, is more directly reflective of management, and reduces the number of patients managed with inconclusive data.

Optimized aminolysis conditions for cleavage of N-protected hydrophobic peptides from solid-phase resins

Solid-phase synthesis and aminolysis cleavage conditions were optimized to obtain N- and C-terminally protected hydrophobic peptides with both high quality and yield. Uncharged 'WALP' peptides, consisting of a central (Leu-Ala)n repeating unit (where n = 5, 10.5 or 11.5) flanked on both sides by Trp 'anchors', and gramicidin A (gA) were synthesized using 9-fluorenylmethoxycarbonyl chemistry from either Wang or Merrifield resins. For WALP peptides, the N-terminal amino acid was capped by coupling N-acetyl- or N-formyl-Ala or -Gly to the peptide/resin or by formylation of the completed peptide/resin with para-nitrophenylformate (p-NPF). N-Terminal acetyl- or formyl-Ala racemized when coupled as an HOBt-ester to the resin-bound peptide, but not when the peptide was formylated with p-NPF. Racemization was avoided at the last step by completing the peptide with acetyl- or formyl-Gly. For both WALP peptides and gA, cleavage conditions using ethanolamine or ethylenediamine were optimized as functions of solvent, time, temperature and resin type. For WALP peptides, maximum yields of highly pure peptide were obtained by cleavage with 20% ethanolamine or ethylenediamine in 80% dichloromethane for 48 h at 24 degrees C. N-Acetyl-protected WALP peptides consistently gave higher yields than those protected with N-formyl. For gA, cleavage with 20% ethanolamine or ethylenediamine in 80% dimethylformamide for 48 h at 24 degrees C gave excellent results. For both WALP peptides and gA, decreasing the cleavage time to 4 h and increasing the temperature to 40-55 degrees C resulted in significantly lower yields. The inclusion of hexafluoroisopropanol in the cleavage solvent mixture did not improve yields for either gA or WALP peptides.

A scaling approach for quantifying the net CO2 flux of the Kuparuk River Basin, Alaska

Net CO₂ flux measurements conducted during the summer and winter of 1994-96 were scaled in space and time to provide estimates of net CO₂ exchange during the 1995-96 (9 May 1995-8 May 1996) annual cycle for the Kuparuk River Basin, a 9200 km² watershed located in NE Alaska. Net CO₂ flux was measured using dynamic chambers and eddy covariance in moist-acidic, nonacidic, wet-sedge, and shrub tundra, which comprise 95% of the terrestrial landscape of the Kuparuk Basin. CO₂ flux data were used as input to multivariate models that calculated instantaneous and daily rates of gross primary production (GPP) and whole-ecosystem respiration (R) as a function of meteorology and ecosystem development. Net CO₂ flux was scaled up to the Kuparuk Basin using a geographical information system (GIS) consisting of a vegetation map, digital terrain map, dynamic temperature and radiation fields, and the models of GPP and R. Basin-wide estimates of net CO₂ exchange for the summer growing season (9 May-5 September 1995) indicate that nonacidic tundra was a net sink of -31.7 ± 21.3 GgC (1 Gg = 10⁹  g), while shrub tundra lost 32.5 ± 6.3 GgC to the atmosphere (negative values denote net ecosystem CO₂ uptake). Acidic and wet sedge tundra were in balance, and when integrated for the entire Kuparuk River Basin (including aquatic surfaces), whole basin summer net CO₂ exchange was estimated to be in balance (-0.9 ± 50.3 GgC). Autumn to winter (6 September 1995-8 May 1996) estimates of net CO₂ flux indicate that acidic, nonacidic, and shrub tundra landforms were all large sources of CO₂ to the atmosphere (75.5 ± 8.3, 96.4 ± 11.4, and 43.3 ± 4.7 GgC for acidic, nonacidic, and shrub tundra, respectively). CO₂ loss from wet sedge surfaces was not substantially different from zero, but the large losses from the other terrestrial landforms resulted in a whole basin net CO₂ loss of 217.2 ± 24.1 GgC during the 1995-96 cold season. When integrated for the 1995-96 annual cycle, acidic (66.4 + 25.25 GgC), nonacidic (64.7 ± 29.2 GgC), and shrub tundra (75.8 ± 8.4 GgC) were substantial net sources of CO₂ to the atmosphere, while wet sedge tundra was in balance (0.4 + 0.8 GgC). The Kuparuk River Basin as a whole was estimated to be a net CO₂ source of 218.1 ± 60.6 GgC over the 1995-96 annual cycle. Compared to direct measurements of regional net CO₂ flux obtained from aircraft-based eddy covariance, the scaling procedure provided realistic estimates of CO₂ exchange during the summer growing season. Although winter estimates could not be assessed directly using aircraft measurements of net CO₂ exchange, the estimates reported here are comparable to measured values reported in the literature. Thus, we have high confidence in the summer estimates of net CO₂ exchange and reasonable confidence in the winter net CO₂ flux estimates for terrestrial landforms of the Kuparuk river basin. Although there is larger uncertainty in the aquatic estimates, the small surface area of aquatic surfaces in the Kuparuk river basin (≈ 5%) presumably reduces the potential for this uncertainty to result in large errors in basin-wide CO₂ flux estimates.

Quantitative analysis of epidermal innervation in Fabry disease

OBJECTIVE

To use skin biopsy specimens to quantitate the cutaneous innervation density of Fabry patients who had preserved renal function.

BACKGROUND

The small fiber neuropathy of Fabry disease is difficult to detect and quantitate by conventional methods. Because this neuropathy is a common characteristic of Fabry disease, quantitating changes in this parameter would be helpful in demonstrating the effectiveness of enzyme or gene replacement therapy.

METHODS

Patients underwent skin biopsy at the thigh and foot. Innervation density was determined by counting free nerve endings in the epidermis. These data were compared with nerve conduction studies, and in selected patients, fiber quantitation of sural nerve biopsy specimens.

RESULTS

The Fabry patients had normal results of nerve conduction studies and large fiber quantitation by sural nerve biopsy. However, the involvement of small cutaneous fibers in these patients was easily demonstrable and quantifiable by skin biopsy. All patients showed severe loss of intraepidermal innervation at the ankle, but fiber loss at the distal thigh was proportionately less severe.

CONCLUSIONS

The nerve damage in Fabry patients with preserved renal function involves exclusively small myelinated and unmyelinated fibers, and skin biopsy is a useful in detecting and quantitating such damage. Comparison of cutaneous innervation density with quantitation of sural nerve biopsy specimens demonstrated that skin biopsy specimens were as sensitive in detecting the presence of neuropathy as were the nerve specimens. It is speculated that analysis of cutaneous innervation may provide a useful marker of the nervous system's response to specific therapy for Fabry disease.

Remembered saccades with variable delay in Parkinson's disease

The effect of increasing delay on the metrics of remembered saccades was studied in 10 subjects with mild Parkinson's disease, none of whom was receiving treatment with L-dopa, and nine age-matched control subjects. Delays of 1 msec, 250 msec, 1000 msec, 2500 msec, and 5000 msec were used, and reflexive saccades used as a control condition. Results were analyzed for the gain of the primary saccade and the accuracy of the final eye position (FEP gain). Reflexive saccades were normal in subjects with Parkinson's disease, but remembered saccades showed marked hypometria of primary saccade gain at all delays. FEP gain was unimpaired in Parkinson's disease, and primary saccade gain and FEP gain did not vary as a function of delay. Hypometria of primary saccades is compatible with dysfunction in striato-collicular inhibitory pathways in Parkinson's disease, arising as a functional consequence of dopamine deficiency in the basal ganglia. Maintenance of an accurate FEP gain suggests no deficit in oculomotor spatial working memory in Parkinson's disease, at least at delays of up to 5 sec.

Laminin alpha2 muscular dystrophy: genotype/phenotype studies of 22 patients

OBJECTIVE

To determine the number of primary laminin alpha2 gene mutations and to conduct genotype/phenotype correlation in a cohort of laminin alpha2-deficient congenital muscular dystrophy patients.

BACKGROUND

Congenital muscular dystrophies (CMD) are a heterogeneous group of muscle disorders characterized by early onset muscular dystrophy and a variable involvement of the CNS. Laminin alpha2 deficiency has been reported in about 40 to 50% of cases of the occidental, classic type of CMD. Laminin alpha2 is a muscle specific isoform of laminin localized to the basal lamina of muscle fibers, where it is thought to interact with myofiber membrane receptor, such as integrins, and possibly dystrophin-associated glycoproteins.

METHODS

Seventy-five CMD patients were tested for laminin alpha2 expression by immunofluorescence and immunoblot. The entire 10 kb laminin alpha2 coding sequence of 22 completely laminin alpha2-deficient patients was screened for causative mutations by reverse transcription (RT)-PCR/single strand conformational polymorphisms (SSCP) analysis and protein truncation test (PTT) analysis followed by automatic sequencing of patient cDNA. Clinical data from the laminin alpha2-deficient patients were collected.

RESULTS

Thirty laminin alpha2-negative patients were identified (40% of CMD patients tested) and 22 of them were screened for laminin alpha2 mutations. Clinical features of laminin alpha2-deficient patients were similar, with severe floppiness at birth, delay in achievement of motor milestones, and MRI findings of white matter changes with normal intelligence. Loss-of-function mutations were identified in 95% (21/22) of the patients studied. SSCP analysis detected laminin alpha2 gene mutations in about 50% of the mutant chromosomes; PTT successfully identified 75% of the mutations. A two base pair deletion mutation at position 2,096-2,097 bp was present in 23% of the patients analyzed.

CONCLUSIONS

Our data suggest that the large majority of laminin alpha2-deficient patients show laminin alpha2 gene mutations.

Aberrant RNA processing in a neurodegenerative disease: the cause for absent EAAT2, a glutamate transporter, in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that is characterized by selective upper and lower motor neuron degeneration, the pathogenesis of which is unknown. About 60%-70% of sporadic ALS patients have a 30%-95% loss of the astroglial glutamate transporter EAAT2 (excitatory amino acid transporter 2) protein in motor cortex and spinal cord. Loss of EAAT2 leads to increased extracellular glutamate and excitotoxic neuronal degeneration. Multiple abnormal EAAT2 mRNAs, including intron-retention and exon-skipping, have now been identified from the affected areas of ALS patients. The aberrant mRNAs were highly abundant and were found only in neuropathologically affected areas of ALS patients but not in other brain regions. They were found in 65% of sporadic ALS patients but were not found in nonneurologic disease or other disease controls. They were also detectable in the cerebrospinal fluid (CSF) of living ALS patients, early in the disease. In vitro expression studies suggest that proteins translated from these aberrant mRNAs may undergo rapid degradation and/ or produce a dominant negative effect on normal EAAT2 resulting in loss of protein and activity. These findings suggest that the loss of EAAT2 in ALS is due to aberrant mRNA and that these aberrant mRNAs could result from RNA processing errors. Aberrant RNA processing could be important in the pathophysiology of neurodegenerative disease and in excitotoxicity. The presence of these mRNA species in ALS CSF may have diagnostic utility.