Efficacy and Safety of the Extreme Lateral Interbody Fusion (XLIF) Technique in Spine Surgery: Meta-Analysis of 1409 Patients.

(1) Objectives: The objective of this study was to quantify the exact clinical-radiological efficacy and safety of the extreme lateral interbody fusion (XLIF) technique in spinal surgery; (2) Methods: A meta-analysis was performed using PubMed, Embase, Scopus, and Cochrane Collaboration Library. Studies focusing on patients surgically treated with XLIF were included. The outcomes were as follows: visual analog scale (VAS) and Oswestry disability index (ODI), radiological outcomes, and adverse events. Cohort studies and case series were also included. Clinical outcomes were assessed at 12 months of age. Data were combined using Review Manager 5.4 and WebPlotDigitizer 13.1.4; (3) Results: Nineteen studies with a pool of 1409 patients were included in this meta-analysis. Leg pain VAS and back pain VAS significantly improved at 12 months (SMD 2.75, 95% CI 0.59-4.90; SMD 4.54, 95% CI 1.39-7.69). ODI showed significant improvement (MD 32.51, 95% CI 24.01-41.00) at 12 months. Disc height increased significantly (SMD -2.73, 95% CI -3.58 to -1.88). Lumbar lordosis and segmental lordosis were significantly corrected postoperatively (MD -2.44, 95% CI -3.45 to -1.43; MD -2.55, 95% CI -3.61 to -1.48). The fusion rates at 12 months ranged from 85.0% to 93.3%. The most frequent complications were transient neurological conditions (2.2%), hardware failure (1.9%), and transient pain (1.8%). The most frequent serious complications were nerve root injury (1.0%), gastrointestinal impairment (0.7%), and vertebral fractures (0.6%); (4) Conclusions: This is the first meta-analysis of the specific use of XLIF in spinal surgery. This study demonstrates that the XLIF technique in spine surgery is associated with good clinical and radiological results and a low complication rate.

Constriction imposed by basement membrane regulates developmental cell migration.

The basement membrane (BM) is a specialized extracellular matrix (ECM), which underlies or encases developing tissues. Mechanical properties of encasing BMs have been shown to profoundly influence the shaping of associated tissues. Here, we use the migration of the border cells (BCs) of the Drosophila egg chamber to unravel a new role of encasing BMs in cell migration. BCs move between a group of cells, the nurse cells (NCs), that are enclosed by a monolayer of follicle cells (FCs), which is, in turn, surrounded by a BM, the follicle BM. We show that increasing or reducing the stiffness of the follicle BM, by altering laminins or type IV collagen levels, conversely affects BC migration speed and alters migration mode and dynamics. Follicle BM stiffness also controls pairwise NC and FC cortical tension. We propose that constraints imposed by the follicle BM influence NC and FC cortical tension, which, in turn, regulate BC migration. Encasing BMs emerge as key players in the regulation of collective cell migration during morphogenesis.

Complications of bronchial thermoplasty using laryngeal mask: case series / Complicaciones de la termoplastia bronquial usando máscara laríngea: serie de casos

Abstract Severe asthma affects more than 250 million people and represents high healthcare costs. Bronchial thermoplasty is a relatively new technique in interventional pulmonology for managing this condition. The procedure is done under general anesthesia and the patients are mostly ASA II and III; therefore, the anesthesia plan must be safe. The purpose of the article is to describe the anesthetic technique used (general anesthesia and laryngeal mask) and the immediate and early complications of the procedure. Four patients were included, each undergoing three sessions. The complications during and immediately after the procedure, as well as the early complications (up to seven days post-procedure) that could have required hospital management were discussed. In three of the sessions at least one acute bronchospasm event presented, but only one patient required hospital admission for more than 24 hours. Experience suggests that thermoplasty may be safely conducted under general anesthesia and laryngeal mask.

Resumen El asma grave afecta a más de 250 millones de personas y genera altos costos en el sistema de salud. La termoplastia bronquial es una técnica relativamente novedosa de la neumología intervencionista para el manejo de esta condición. Este procedimiento se realiza bajo anestesia general, y los pacientes son en su mayoría ASA II y III, por lo que el plan anestésico debe ser seguro. El objetivo del artículo es describir la técnica anestésica utilizada (anestesia general y máscara laríngea) y las complicaciones inmediatas y tempranas del procedimiento. Se incluyeron cuatro pacientes, cada uno de los cuales fue sometido a tres sesiones. Se describieron las complicaciones durante e inmediatamente después del procedimiento y las complicaciones tempranas (hasta siete días posprocedimiento), que hubieran requerido manejo hospitalario. En tres de las sesiones se presentó al menos un evento agudo de broncoespasmo y solo un paciente requirió hospitalización mayor a 24 horas. La experiencia sugiere que la termoplastia puede ser llevada a cabo de manera segura bajo anestesia general y mascara laríngea.

Características socioeconómicas y sociodemográficas de las familias de pacientes hospitalizados en el Instituto Nacional de Salud San Borja, 2018 / Socioeconomic and sociodemographic characteristics of the family members of patients hospitalized in the Instituto Nacional de Salud del Niño San Borja, 2018

RESUMEN Objetivo: Describir las características familiares y sociales de los pacientes hospitalizados en el Instituto Nacional de Salud del Niño San Borja durante los meses de abril a diciembre de 2018. Materiales y métodos: Investigación descriptiva, observacional y analítica. La selección de la muestra fue probabilística de un universo de 4383 pacientes. La muestra fue de 573 pacientes, con un nivel de confianza de 96 %, y un margen de error de 4,00 %. El instrumento empleado fue la ficha de recolección de datos de la historia clínica. La información se procesó con el paquete estadístico SPSS. Resultados: El 47,12 % de los pacientes proceden de Lima Metropolitana; el 2,97 %, de la Provincia Constitucional del Callao, y el 49,91 % del interior del país, lo que incluye Lima Provincia. El 73,65 % de pacientes vive en condición de pobreza; el 24,26 % tiene condición de pobreza extrema; y solo el 2,09 % son considerados no pobres. El 40,49 % de pacientes habita en viviendas en condiciones inadecuadas. La mayoría de los participantes son beneficiarios del Seguro Integral de Salud (SIS) (94,24 %). Respecto al nivel educativo de las madres, el 1,92 % no tiene instrucción y el 7,68 % no concluyeron los estudios primarios. El 0,52 % de los padres no tienen instrucción, y el 4,19 % tienen estudios primarios incompletos. En cuanto a la educación básica regular (EBR), 43,11 % de las madres y 39,3 % de los padres la concluyeron; mientras que solo 9,77 % del grupo masculino y 6,63 % del femenino cuentan con educación superior técnica. Conclusiones: El estudio permitió un acercamiento a las condiciones socioeconómicas de los pacientes, en tanto determinantes de la salud. Se evidencia que la mayoría de pacientes viven en condición de pobreza y pobreza extrema. Un porcentaje significativo procede de los diferentes departamentos del país, lo que refleja el centralismo nacional en cuanto a los centros pediátricos especializados y, a la vez, evidencia la importancia del enfoque de interculturalidad en salud. El tipo de seguro de salud está relacionado con la condición económica: se corrobora que la mayoría es beneficiaria del Seguro Integral de Salud (SIS) y vive en condición de pobreza y pobreza extrema. La condición económica del paciente guarda relación con la proporción de viviendas que no cumplen con los requerimientos mínimos de habitabilidad, lo cual es un factor de riesgo para pacientes con enfermedades crónicas o postrasplantados (médula ósea y órganos sólidos). Finalmente, los padres de familia muestran un mayor nivel de instrucción que las madres, lo cual podría sugerir una brecha de género.

ABSTRACT Objective: To describe the family and social characteristics of patients hospitalized in the Instituto Nacional de Salud del Niño San Borja from April to December 2018. Materials and methods: A descriptive, observational and analytical research. Probability sampling was used in a study population of 4,383 patients. The sample consisted of 573 patients, with a 96 % confidence level and a 4 % margin of error. A data collection sheet included in the medical record was used as instrument. The data was processed using the IBM SPSS Statistics statistical software. Results: Forty-seven point one two percent (47.12 %) of the patients came from Lima Metropolitan Area, 2.97 % from the Constitutional Province of Callao, and 49.91 % from inland, including Lima Province. Seventy-three point six five percent (73.65 %) of the patients lived in poverty, 24.26 % lived in extreme poverty, and only 2.09 % were not considered poor. Forty point four nine percent (40.49 %) of the patients lived in unsuitable housing conditions. Most study subjects were holders of the Comprehensive Health Insurance (SIS) (94.24 %). Regarding the mothers' and fathers' educational level, 1.92 % and 0.52 % received no education, and 7.68 % and 4.19 % did not finish primary school, respectively. Forty-three point one one percent (43.11 %) of the mothers and 39.3 % of the fathers finished the regular basic education (EBR). Nine point seven seven percent (9.77 %) of the fathers and only 6.63 % of the mothers had higher technical education. Conclusions: The study enabled us to take a close look to the patients' socioeconomic conditions, which definitely affect their health. It showed that most patients live in poverty and extreme poverty. A significant percentage of the patients come from the different departments of Peru. This situation reflects the centralism prevailing in the specialized pediatric centers and demonstrates the importance of the intercultural approach in health. The type of insurance is related to the patients' economic status. It was confirmed that most of them hold the SIS and live in poverty or extreme poverty. The patients' low economic status is related to dwellings which do not comply with minimum housing standards. This fact is a risk factor for patients with chronic diseases or who got a transplant (bone marrow and solid organs). Finally, fathers evidenced a higher education level than mothers, which could suggest a gender gap.

Ralstonia spp. in a dialysis unit: an experience in the identification and control of an outbreak / Ralstonia spp. en una unidad de diálisis: experiencia en la identificación y control de brote

Abstract Objective: to describe an experience in identification and control of an outbreak of Ralstonia spp. in a renal unit. Material and Method: an epidemiological investigation of a hospital outbreak in 2 sites and extramural service of a renal unit. The investigation included patients who presented fever or chills, during or after dialysis, and who had positive blood culture for Ralstonia spp. Results: Of 769 hemodialysis patients, 124 were identified with bacteremia by Ralstonia spp.; of these, 98.4% had catheter access and 1.6% had fistula. The overall attack rate was 16.1% and the case fatality rate was 0.8%. Environmental cultures were taken and drugs and devices were tracked. Several cultures were taken of the prefilled heparin following the methods described in the International Pharmacopoeia. However, it was the technique of microbial isolation recommended by experts that enabled the isolation of the microorganism and confirmed the source. Conclusions: The outbreak described exceeded the number of patients affected documented in literature. It was caused by a contaminated batch of heparin. Evidence is provided of a recommended by expert technique used for the isolation of Ralstonia spp. in order to achieve control of outbreaks in a timely manner, minimizing clinical, economic, and social impact.

Resumen Objetivo: describir la experiencia en la identificación y control de un brote por Ralstonia spp. en una unidad renal. Material y Método: investigación epidemiológica de brote hospitalario en 2 sedes y servicio extramural de una unidad renal. Se incluyeron pacientes que presentaron fiebre o escalofrío, durante o después de la terapia dialítica, y que tuvieran hemocultivo positivo para Ralstonia spp. Resultados: De los 709 pacientes para hemodiálisis, se identificaron 124 con bacteriemia por Ralstonia spp., 98,4% tenían acceso por catéter. La tasa de ataque global fue del 16,1% y la tasa de letalidad 0,8%. Se realizaron cultivos ambientales y trazabilidad de medicamentos y dispositivos, pero ante la presencia de casos extramurales la hipótesis fue redireccionada. La heparina prellenada había sido cultivada en varias oportunidades siguiendo la metodología de la farmacopea internacional. Sin embargo, la técnica de aislamiento microbiano recomendada por expertos fue la que permitió aislar el microorganismo y confirmar la fuente. Conclusiones: El brote que se describe excedió el número de pacientes documentados en la literatura y fue causado por un lote contaminado de heparina. Se aporta evidencia de una técnica recomendada por expertos utilizada para el aislamiento de Ralstonia spp. a fin de lograr el control de brotes de manera oportuna, minimizando el impacto clínico, económico y social.

Integrins regulate epithelial cell shape by controlling the architecture and mechanical properties of basal actomyosin networks.

Forces generated by the actomyosin cytoskeleton are key contributors to many morphogenetic processes. The actomyosin cytoskeleton organises in different types of networks depending on intracellular signals and on cell-cell and cell-extracellular matrix (ECM) interactions. However, actomyosin networks are not static and transitions between them have been proposed to drive morphogenesis. Still, little is known about the mechanisms that regulate the dynamics of actomyosin networks during morphogenesis. This work uses the Drosophila follicular epithelium, real-time imaging, laser ablation and quantitative analysis to study the role of integrins on the regulation of basal actomyosin networks organisation and dynamics and the potential contribution of this role to cell shape. We find that elimination of integrins from follicle cells impairs F-actin recruitment to basal medial actomyosin stress fibers. The available F-actin redistributes to the so-called whip-like structures, present at tricellular junctions, and into a new type of actin-rich protrusions that emanate from the basal cortex and project towards the medial region. These F-actin protrusions are dynamic and changes in total protrusion area correlate with periodic cycles of basal myosin accumulation and constriction pulses of the cell membrane. Finally, we find that follicle cells lacking integrin function show increased membrane tension and reduced basal surface. Furthermore, the actin-rich protrusions are responsible for these phenotypes as their elimination in integrin mutant follicle cells rescues both tension and basal surface defects. We thus propose that the role of integrins as regulators of stress fibers plays a key role on controlling epithelial cell shape, as integrin disruption promotes reorganisation into other types of actomyosin networks, in a manner that interferes with proper expansion of epithelial basal surfaces.

Optical flow analysis reveals that Kinesin-mediated advection impacts the orientation of microtubules in the Drosophila oocyte.

The orientation of microtubule (MT) networks is exploited by motors to deliver cargoes to specific intracellular destinations and is thus essential for cell polarity and function. Reconstituted in vitro systems have largely contributed to understanding the molecular framework regulating the behavior of MT filaments. In cells, however, MTs are exposed to various biomechanical forces that might impact on their orientation, but little is known about it. Oocytes, which display forceful cytoplasmic streaming, are excellent model systems to study the impact of motion forces on cytoskeletons in vivo. Here we implement variational optical flow analysis as a new approach to analyze the polarity of MTs in the Drosophila oocyte, a cell that displays distinct Kinesin-dependent streaming. After validating the method as robust for describing MT orientation from confocal movies, we find that increasing the speed of flows results in aberrant plus end growth direction. Furthermore, we find that in oocytes where Kinesin is unable to induce cytoplasmic streaming, the growth direction of MT plus ends is also altered. These findings lead us to propose that cytoplasmic streaming - and thus motion by advection - contributes to the correct orientation of MTs in vivo. Finally, we propose a possible mechanism for a specialized cytoplasmic actin network (the actin mesh) to act as a regulator of flow speeds to counteract the recruitment of Kinesin to MTs.

YAP/Yorkie in the germline modulates the age-related decline of germline stem cells and niche cells.

The properties and behaviour of stem cells rely heavily on signaling from the local microenvironment. At the apical end of Drosophila testis, self-renewal and differentiation of germline stem cells (GSCs) are tightly controlled by distinct somatic cells that comprise a specialised stem cell niche known as the hub. The hub maintains GSC homeostasis through adhesion and cell signaling. The Salvador/Warts/Hippo (SWH) pathway, which suppresses the transcriptional co-activator YAP/Yki via a kinase cascade, is a known regulator of stem cell proliferation and differentiation. Here, we show that increasing YAP/Yki expression in the germline, as well as reducing Warts levels, blocks the decrease of GSC numbers observed in aging flies, with only a small increase on their proliferation. An increased expression of YAP/Yki in the germline or a reduction in Warts levels also stymies an age-related reduction in hub cell number, suggesting a bilateral relationship between GSCs and the hub. Conversely, RNAi-based knockdown of YAP/Yki in the germline leads to a significant drop in hub cell number, further suggesting the existence of such a SC-to-niche relationship. All together, our data implicate the SWH pathway in Drosophila GSC maintenance and raise questions about its role in stem cell homeostasis in aging organisms.

Active diffusion and advection in Drosophila oocytes result from the interplay of actin and microtubules.

Transport in cells occurs via a delicate interplay of passive and active processes, including diffusion, directed transport and advection. Despite progress in super-resolution microscopy, discriminating and quantifying these processes is a challenge, requiring tracking of rapidly moving, sub-diffraction objects in a crowded, noisy environment. Here we use differential dynamic microscopy with different contrast mechanisms to provide a thorough characterization of the dynamics in the Drosophila oocyte. We study the movement of vesicles and the elusive motion of a cytoplasmic F-actin mesh, a known regulator of cytoplasmic flows. We find that cytoplasmic motility constitutes a combination of directed motion and random diffusion. While advection is mainly attributed to microtubules, we find that active diffusion is driven by the actin cytoskeleton, although it is also enhanced by the flow. We also find that an important dynamic link exists between vesicles and cytoplasmic F-actin motion, as recently suggested in mouse oocytes.

DrosAfrica: Building an African biomedical research community using Drosophila.

The impact that research has on shaping the future of societies is perhaps as significant as never before. One of the problems for most regions in Africa is poor quality and quantity of research-based education, as well as low level of funding. Hence, African researchers produce only around one percent of the world's research. We believe that research with Drosophila melanogaster can contribute to changing that. As seen before in other places, Drosophila can be used as a powerful and cost-effective model system to scale-up and improve both academia and research output. The DrosAfrica project was founded to train and establish a connected community of researchers using Drosophila as a model system to investigate biomedical problems in Africa. Since founding, the project has trained eighty scientists from numerous African countries, and continues to grow. Here, we describe the DrosAfrica project, its conception and its mission. We also give detailed insights into DrosAfrica's approaches to achieve its aims, as well as future perspectives, and opportunities beyond Africa.

α-Spectrin and integrins act together to regulate actomyosin and columnarization, and to maintain a monolayered follicular epithelium.

The spectrin cytoskeleton crosslinks actin to the membrane, and although it has been greatly studied in erythrocytes, much is unknown about its function in epithelia. We have studied the role of spectrins during epithelia morphogenesis using the Drosophila follicular epithelium (FE). As previously described, we show that α-Spectrin and ß-Spectrin are essential to maintain a monolayered FE, but, contrary to previous work, spectrins are not required to control proliferation. Furthermore, spectrin mutant cells show differentiation and polarity defects only in the ectopic layers of stratified epithelia, similar to integrin mutants. Our results identify α-Spectrin and integrins as novel regulators of apical constriction-independent cell elongation, as α-Spectrin and integrin mutant cells fail to columnarize. Finally, we show that increasing and reducing the activity of the Rho1-Myosin II pathway enhances and decreases multilayering of α-Spectrin cells, respectively. Similarly, higher Myosin II activity enhances the integrin multilayering phenotype. This work identifies a primary role for α-Spectrin in controlling cell shape, perhaps by modulating actomyosin. In summary, we suggest that a functional spectrin-integrin complex is essential to balance adequate forces, in order to maintain a monolayered epithelium.

Planar cell polarity: the Dachsous/Fat system contributes differently to the embryonic and larval stages of Drosophila.

The epidermal patterns of all three larval instars (L1-L3) ofDrosophilaare made by one unchanging set of cells. The seven rows of cuticular denticles of all larval stages are consistently planar polarised, some pointing forwards, others backwards. In L1 all the predenticles originate at the back of the cells but, in L2 and L3, they form at the front or the back of the cell depending on the polarity of the forthcoming denticles. We find that, to polarise all rows, the Dachsous/Fat system is differentially utilised; in L1 it is active in the placement of the actin-based predenticles but is not crucial for the final orientation of the cuticular denticles, in L2 and L3 it is needed for placement and polarity. We find Four-jointed to be strongly expressed in the tendon cells and show how this might explain the orientation of all seven rows. Unexpectedly, we find that L3 that lack Dachsous differ from larvae lacking Fat and we present evidence that this is due to differently mislocalised Dachs. We make some progress in understanding how Dachs contributes to phenotypes of wildtype and mutant larvae and adults.

Integrins regulate epithelial cell differentiation by modulating Notch activity.

Coordinating exit from the cell cycle with differentiation is crucial for proper development and tissue homeostasis. Failure to do so can lead to aberrant organogenesis and tumorigenesis. However, little is known about the developmental signals that regulate the switch from cell cycle exit to differentiation. Signals downstream of two key developmental pathways, Notch and Salvador-Warts-Hippo (SWH), and signals downstream of myosin activity regulate this switch during the development of the follicle cell epithelium of the Drosophila ovary. Here, we have identified a fourth player, the integrin signaling pathway. Elimination of integrin function blocks the mitosis-to-endocycle switch and differentiation in posterior follicle cells (PFCs), by regulation of the cyclin-dependent kinase inhibitor (CKI) dacapo. In addition, integrin-mutant PFCs show defective Notch signaling and endocytosis. Furthermore, integrins act in PFCs by modulating the activity of the Notch pathway, as reducing the amount of Hairless, the major antagonist of Notch, or misexpressing Notch intracellular domain rescues the cell cycle and differentiation defects. Taken together, our findings reveal a direct involvement of integrin signaling on the spatial and temporal regulation of epithelial cell differentiation during development.

Hop-on hop-off: polysomes take a tour of the cell on endosomes.

After export from the nucleus, ribosomes need to be distributed throughout the entire cell so that protein synthesis can occur even at distant sites. In the elongated hyphal cell of the fungus Ustilago maydis, Higuchi et al. (2014. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201307164) now demonstrate that polysomes associate with early endosomes that undergo kinesin 3- and dynein-dependent long-range motility. The bidirectional movement of early endosomes randomly distributes polysomes, which may ensure the even distribution of the translation machinery across the entire cell.

Plasticity of both planar cell polarity and cell identity during the development of Drosophila.

Drosophila has helped us understand the genetic mechanisms of pattern formation. Particularly useful have been those organs in which different cell identities and polarities are displayed cell by cell in the cuticle and epidermis (Lawrence, 1992; Bejsovec and Wieschaus, 1993; Freeman, 1997). Here we use the pattern of larval denticles and muscle attachments and ask how this pattern is maintained and renewed over the larval moult cycles. During larval growth each epidermal cell increases manyfold in size but neither divides nor dies. We follow individuals from moult to moult, tracking marked cells and find that, as cells are repositioned and alter their neighbours, their identities change to compensate and the pattern is conserved. Single cells adopting a new fate may even acquire a new polarity: an identified cell that makes a forward-pointing denticle in the first larval stage may make a backward-pointing denticle in the second and third larval stages. DOI: http://dx.doi.org/10.7554/eLife.01569.001.

The auto-inhibitory domain and ATP-independent microtubule-binding region of Kinesin heavy chain are major functional domains for transport in the Drosophila germline.

The major motor Kinesin-1 provides a key pathway for cell polarization through intracellular transport. Little is known about how Kinesin works in complex cellular surroundings. Several cargos associate with Kinesin via Kinesin light chain (KLC). However, KLC is not required for all Kinesin transport. A putative cargo-binding domain was identified in the C-terminal tail of fungal Kinesin heavy chain (KHC). The tail is conserved in animal KHCs and might therefore represent an alternative KLC-independent cargo-interacting region. By comprehensive functional analysis of the tail during Drosophila oogenesis we have gained an understanding of how KHC achieves specificity in its transport and how it is regulated. This is, to our knowledge, the first in vivo structural/functional analysis of the tail in animal Kinesins. We show that the tail is essential for all functions of KHC except Dynein transport, which is KLC dependent. These tail-dependent KHC activities can be functionally separated from one another by further characterizing domains within the tail. In particular, our data show the following. First, KHC is temporally regulated during oogenesis. Second, the IAK domain has an essential role distinct from its auto-inhibitory function. Third, lack of auto-inhibition in itself is not necessarily detrimental to KHC function. Finally, the ATP-independent microtubule-binding motif is required for cargo localization. These results stress that two unexpected highly conserved domains, namely the auto-inhibitory IAK and the auxiliary microtubule-binding motifs, are crucial for transport by Kinesin-1 and that, although not all cargos are conserved, their transport involves the most conserved domains of animal KHCs.

Nonsense-mediated mRNA decay: from mechanistic insights to impacts on human health.

Cells are able to recognize and degrade aberrant transcripts in order to self-protect from potentially toxic proteins. Various pathways detect aberrant RNAs in the cytoplasm and are dependent on translation. One of these pathways is the nonsense-mediated RNA decay (NMD). NMD is a surveillance mechanism that degrades transcripts containing nonsense mutations, preventing the translation of possibly harmful truncated proteins. For example, the degradation of a nonsense harming ß-globin allele renders normal phenotypes. On the other hand, regulating NMD is also important in those cases when the produced aberrant protein is better than having no protein, as it has been shown for cystic fibrosis. These findings reflect the important role for NMD in human health. In addition, NMD controls the levels of physiologic transcripts, which defines this pathway as a novel gene expression regulator, with huge impact on homeostasis, cell growth and development. While the mechanistic details of NMD are being gradually understood, the physiological role of this RNA surveillance pathway still remains largely unknown. This is a brief and simplified review on various aspects of NMD, such as the nature of the NMD targets, the mechanism of target degradation and the links between NMD and cell growth, animal development and diseases.

Cytoplasmic streaming in Drosophila oocytes varies with kinesin activity and correlates with the microtubule cytoskeleton architecture.

Cells can localize molecules asymmetrically through the combined action of cytoplasmic streaming, which circulates their fluid contents, and specific anchoring mechanisms. Streaming also contributes to the distribution of nutrients and organelles such as chloroplasts in plants, the asymmetric position of the meiotic spindle in mammalian embryos, and the developmental potential of the zygote, yet little is known quantitatively about the relationship between streaming and the motor activity which drives it. Here we use Particle Image Velocimetry to quantify the statistical properties of Kinesin-dependent streaming during mid-oogenesis in Drosophila. We find that streaming can be used to detect subtle changes in Kinesin activity and that the flows reflect the architecture of the microtubule cytoskeleton. Furthermore, based on characterization of the rheology of the cytoplasm in vivo, we establish estimates of the number of Kinesins required to drive the observed streaming. Using this in vivo data as the basis of a model for transport, we suggest that the disordered character of transport at mid-oogenesis, as revealed by streaming, is an important component of the localization dynamics of the body plan determinant oskar mRNA.

Drosophila Upf1 and Upf2 loss of function inhibits cell growth and causes animal death in a Upf3-independent manner.

Nonsense-mediated RNA decay (NMD) is a surveillance mechanism that degrades transcripts containing nonsense mutations, preventing the translation of truncated proteins. NMD also regulates the levels of many endogenous mRNAs. While the mechanism of NMD is gradually understood, its physiological role remains largely unknown. The core NMD genes upf1 and upf2 are essential in several organisms, which may reflect an important developmental role for NMD. Alternatively, the lethality of these mutants might arise from their function in NMD-independent processes. To analyze the developmental importance of NMD, we studied Drosophila mutants of the other core NMD gene, upf3. We compare the resulting upf3 phenotype with those defects observed in upf1 and upf2 loss-of-function mutants, as well as with flies expressing a mutant Upf2 protein unable to bind Upf3. Our results show that Upf3 is an NMD effector in the fly but, unlike Upf1 and Upf2, plays a peripheral role in the degradation of most NMD targets and is not required for development or viability. Furthermore, Upf1 and Upf2 loss-of-function inhibits cell growth and induces apoptosis through a Upf3-independent pathway. Accordingly, disruption of Upf2-Upf1 interaction causes death, while the Upf2-Upf3 complex is dispensable for viability. Our findings suggest that NMD is essential for cell growth and animal development, and that the lethality of upf1 and upf2 mutants is not due to disrupting their roles during NMD-independent processes, but to their function in the degradation of specific mRNAs by the NMD pathway. Furthermore, our results show that Upf3 is not always essential in NMD.

Nonsense-mediated mRNA decay and development: shoot the messenger to survive?

NMD (nonsense-mediated mRNA decay) is a surveillance mechanism that degrades transcripts containing nonsense mutations, preventing the translation of potentially harmful truncated proteins. Although the mechanistic details of NMD are gradually being understood, the physiological role of this RNA surveillance pathway still remains largely unknown. The core NMD genes Upf1 (up-frameshift suppressor 1) and Upf2 are essential for animal viability in the fruitfly, mouse and zebrafish. These findings may reflect an important role for NMD during animal development. Alternatively, the lethal phenotypes of upf1 and upf2 mutants might be due to their function in NMD-independent processes. In the present paper, we describe the phenotypes observed when the NMD factors are mutated in various organisms, and discuss findings that might shed light on the function of NMD in cellular growth and development of an organism.