Semaphorin 6A in Retinal Ganglion Cells Regulates Functional Specialization of the Inner Retina.

To form functional circuits, neurons must settle in their appropriate cellular locations and then project and elaborate neurites to contact their target synaptic neuropils. Laminar organization within the vertebrate retinal inner plexiform layer (IPL) facilitates pre- and postsynaptic neurite targeting, yet, the precise mechanisms underlying establishment of functional IPL subdomains are not well understood. Here we explore mechanisms defining the compartmentalization of OFF and ON neurites generally, and OFF and ON direction-selective neurites specifically, within the developing IPL. We show that semaphorin 6A (Sema6A), a repulsive axon guidance cue, is required for delineation of OFF versus ON circuits within the IPL: in the Sema6a null IPL, the boundary between OFF and ON domains is blurred. Furthermore, Sema6A expressed by retinal ganglion cells (RGCs) directs laminar segregation of OFF and ON starburst amacrine cell (SAC) dendritic scaffolds, which themselves serve as a substrate upon which other retinal neurites elaborate. These results demonstrate for the first time that RGCs, the first neuron-type born within the retina, play an active role in functional specialization of the IPL. Retinal ganglion cell-dependent regulation of OFF and ON starburst amacrine cell dendritic scaffold segregation prevents blurring of OFF versus ON functional domains in the murine inner plexiform layer.

Binary Fate Choice between Closely Related Interneuronal Types Is Determined by a Fezf1-Dependent Postmitotic Transcriptional Switch.

Many neuronal types occur as pairs that are similar in most respects but differ in a key feature. In some pairs of retinal neurons, called paramorphic, one member responds to increases and the other to decreases in luminance (ON and OFF responses). Here, we focused on one such pair, starburst amacrine cells (SACs), to explore how closely related neuronal types diversify. We find that ON and OFF SACs are transcriptionally distinct prior to their segregation, dendritic outgrowth, and synapse formation. The transcriptional repressor Fezf1 is selectively expressed by postmitotic ON SACs and promotes the ON fate and gene expression program while repressing the OFF fate and program. The atypical Rho GTPase Rnd3 is selectively expressed by OFF SACs and regulates their migration but is repressed by Fezf1 in ON SACs, enabling differential positioning of the two types. These results define a transcriptional program that controls diversification of a paramorphic pair.

Establishing Wiring Specificity in Visual System Circuits: From the Retina to the Brain.

The retina is a tremendously complex image processor, containing numerous cell types that form microcircuits encoding different aspects of the visual scene. Each microcircuit exhibits a distinct pattern of synaptic connectivity. The developmental mechanisms responsible for this patterning are just beginning to be revealed. Furthermore, signals processed by different retinal circuits are relayed to specific, often distinct, brain regions. Thus, much work has focused on understanding the mechanisms that wire retinal axonal projections to their appropriate central targets. Here, we highlight recently discovered cellular and molecular mechanisms that together shape stereotypic wiring patterns along the visual pathway, from within the retina to the brain. Although some mechanisms are common across circuits, others play unconventional and circuit-specific roles. Indeed, the highly organized connectivity of the visual system has greatly facilitated the discovery of novel mechanisms that establish precise synaptic connections within the nervous system.

What is orthopaedic triage? A systematic review.

RATIONALE, AIMS AND OBJECTIVES: Complex and chronic disease is placing significant pressure on hospital outpatient departments. Novel ways of delivering care have been developed recently and are often described as 'triage' services. This paper reviews the literature pertaining to definitions and descriptions of orthopaedic/musculoskeletal triage processes, in order to provide information on 'best practice' to assist health care facilities. METHOD: A comprehensive open-ended search was conducted using electronic databases to identify studies describing models of triage clinics for patients with a musculoskeletal/orthopaedic complaint, who have been referred to hospital outpatient clinics for a surgical consultation. Studies were critically appraised using the McMaster quality appraisal tool and ranked using the National Health and Medical Research Council hierarchy of evidence. A thematic analysis of the definitions, processes and procedures of triage described within the literature was undertaken. RESULTS: 1930 studies were identified and 45 were included in the review (including diagnostic and evaluative research). The hierarchy of evidence ranged from I to IV; however, the majority were at low levels of evidence and scored poorly on the critical appraisal tool. Three broad themes of triage were identified: presence of a referral, configuration of the triage (who, how and where) and the aim of triage. However, there were significant inconsistencies across these themes. CONCLUSIONS: This systematic review highlighted the need for standardization of the definition of triage, the procedures of assessment and management and measures of outcome used in orthopaedic/musculoskeletal triage to ensure best-practice processes, procedures and outcomes for triage clinics.

Crimpy enables discrimination of presynaptic and postsynaptic pools of a BMP at the Drosophila neuromuscular junction.

Distinct pools of the bone morphogenetic protein (BMP) Glass bottom boat (Gbb) control structure and function of the Drosophila neuromuscular junction. Specifically, motoneuron-derived Gbb regulates baseline neurotransmitter release, whereas muscle-derived Gbb regulates neuromuscular junction growth. Yet how cells differentiate between these ligand pools is not known. Here we present evidence that the neuronal Gbb-binding protein Crimpy (Cmpy) permits discrimination of pre- and postsynaptic ligand by serving sequential functions in Gbb signaling. Cmpy first delivers Gbb to dense core vesicles (DCVs) for activity-dependent release from presynaptic terminals. In the absence of Cmpy, Gbb is no longer associated with DCVs and is not released by activity. Electrophysiological analyses demonstrate that Cmpy promotes Gbb's proneurotransmission function. Surprisingly, the Cmpy ectodomain is itself released upon DCV exocytosis, arguing that Cmpy serves a second function in BMP signaling. In addition to trafficking Gbb to DCVs, we propose that Gbb/Cmpy corelease from presynaptic terminals defines a neuronal protransmission signal.

Postmenopausal serum sex steroids and risk of hormone receptor-positive and -negative breast cancer: a nested case-control study.

Prediagnostic endogenous sex steroid hormone levels have well established associations with overall risk of breast cancer. While evidence toward the existence of distinct subtypes of breast cancer accumulates, few studies have investigated the associations of sex steroid hormone levels with risk of hormone receptor [estrogen receptor (ER) and/or progesterone receptor (PR)] defined breast cancer. In a case-control study nested within the EPIC cohort (European Prospective Investigation into Cancer and Nutrition), estradiol, testosterone, and sex hormone-binding globulin levels were measured in prediagnostic serum samples from postmenopausal women not using hormone replacement therapy at blood donation. A total of 554 women who developed invasive breast cancer with information on receptor status were matched with 821 control subjects. Conditional logistic regression models estimated breast cancer risk with hormone concentrations according to hormone receptor status of the tumor. Sex steroid hormones were associated with risks of not only ER+PR+ breast cancer [estradiol OR for highest vs. lowest tertile = 2.91 (95% CI: 1.62-5.23), P(trend) = 0.002; testosterone OR = 2.27 (95% CI: 1.35-3.81), P(trend) = 0.002] but also of ER-PR- breast cancer [estradiol OR = 2.11 (95% CI: 1.00-4.46), P(trend) = 0.05; testosterone OR = 2.06 (95% CI: 0.95-4.46), P(trend) = 0.03], with associations appearing somewhat stronger in the receptor-positive disease. Serum androgens and estrogens are associated with risks of both hormone receptor-negative as well as receptor-positive breast tumors. Further research is needed to establish through which molecular pathways, and during which evolutionary stages of development, androgens and estrogens can promote the occurrence of both receptor-positive and -negative clinical breast tumors.

Crimpy inhibits the BMP homolog Gbb in motoneurons to enable proper growth control at the Drosophila neuromuscular junction.

The BMP pathway is essential for scaling of the presynaptic motoneuron arbor to the postsynaptic muscle cell at the Drosophila neuromuscular junction (NMJ). Genetic analyses indicate that the muscle is the BMP-sending cell and the motoneuron is the BMP-receiving cell. Nevertheless, it is unclear how this directionality is established as Glass bottom boat (Gbb), the known BMP ligand, is active in motoneurons. We demonstrate that crimpy (cmpy) limits neuronal Gbb activity to permit appropriate regulation of NMJ growth. cmpy was identified in a screen for motoneuron-expressed genes and encodes a single-pass transmembrane protein with sequence homology to vertebrate Cysteine-rich transmembrane BMP regulator 1 (Crim1). We generated a targeted deletion of the cmpy locus and find that loss-of-function mutants exhibit excessive NMJ growth. In accordance with its expression profile, tissue-specific rescue experiments indicate that cmpy functions neuronally. The overgrowth in cmpy mutants depends on the activity of the BMP type II receptor Wishful thinking, arguing that Cmpy acts in the BMP pathway upstream of receptor activation and raising the possibility that it inhibits Gbb activity in motoneurons. Indeed, the cmpy mutant phenotype is strongly suppressed by RNAi-mediated knockdown of Gbb in motoneurons. Furthermore, Cmpy physically interacts with the Gbb precursor protein, arguing that Cmpy binds Gbb prior to the secretion of mature ligand. These studies demonstrate that Cmpy restrains Gbb activity in motoneurons. We present a model whereby this inhibition permits the muscle-derived Gbb pool to predominate at the NMJ, thus establishing the retrograde directionality of the pro-growth BMP pathway.

A case study evaluation of ethics review systems for multicentre clinical trials.

OBJECTIVE: To evaluate the difference in time taken for ethics and site governance approval for multicentre clinical trials using two different systems of ethics review. DESIGN: We evaluated the times to final ethics and governance approval for two international, multicentre clinical trials of treatment for metastatic colorectal cancer: the MAX trial, using a non-centralised ethics review system, and the CO.20 trial, using the new New South Wales centralised ethics review system. MAIN OUTCOME MEASURE: Time from trial submission to overall study approval. RESULTS: The median time taken to obtain ethics approval for the MAX trial at 16 NSW sites was 100 days (range, 36-161 days). The median time to obtain central ethics approval for the CO.20 trial at 14 NSW sites was 77 days, with an additional 60 days (range 20-79 days) required to obtain site-specific research governance approval. CONCLUSIONS: Any difference in time to approval between the review systems was outweighed by the overall time taken. However, the time spent by both the coordinating centre and local sites in collation, submission and correspondence was greatly reduced, and the centralised process allowed for standardised documentation at all study sites.