Motor axons approach muscles that are prepatterned in the prospective synaptic region. In mice, prepatterning of acetylcholine receptors requires Lrp4, a LDLR family member, and MuSK, a receptor tyrosine kinase. Lrp4 can bind and stimulate MuSK, strongly suggesting that association between Lrp4 and MuSK, independent of additional ligands, initiates prepatterning in mice. In zebrafish, Wnts, which bind the Frizzled (Fz)-like domain in MuSK, are required for prepatterning, suggesting that Wnts may contribute to prepatterning and neuromuscular development in mammals. We show that prepatterning in mice requires Lrp4 but not the MuSK Fz-like domain. In contrast, prepatterning in zebrafish requires the MuSK Fz-like domain but not Lrp4. Despite these differences, neuromuscular synapse formation in zebrafish and mice share similar mechanisms, requiring Lrp4, MuSK, and neuronal Agrin but not the MuSK Fz-like domain or Wnt production from muscle. Our findings demonstrate that evolutionary divergent mechanisms establish muscle prepatterning in zebrafish and mice.
Cognitive control tasks require using one class of information while ignoring competing classes of information. The central role of the medial prefrontal cortex (mPFC) in cognitive control is well established in the primate literature, and largely accepted in the rodent literature because mPFC damage causes deficits in tasks that may require cognitive control, as inferred, typically from the task design. In prior work we used an active place avoidance task where a rat or mouse on a rotating arena is required to avoid the stationary task-relevant locations of a mild shock and ignore the rotating task-irrelevant locations of those shocks. The task is impaired by hippocampal manipulations, and the discharge of hippocampal place cell populations judiciously alternates between representing stationary locations near the shock zone and rotating locations far from the shock zone, demonstrating cognitive control concurrently in behavior and the hippocampal representation of spatial information. Here we test whether rat mPFC lesion impairs the active place avoidance task to evaluate two competing hypotheses, a “central-computation” hypothesis that the mPFC is essential for the computations required for cognitive control and an alternative “local-computation” hypothesis that other brain areas can perform the computations required for cognitive control, independent of mPFC. Ibotenic acid lesion of the mPFC was effective, damaging the cingulate, prelimbic and infralimbic cortices. The lesion also altered the normal coordination of metabolic activity across remaining structures. The lesion did not impair learning to avoid the initial location of shock or long-term place avoidance memory, but impaired avoidance after the shock was relocated. The lesion also did not impair the alternation between task-relevant and task-irrelevant hippocampal representations of spatial information. These findings support the local-computation hypothesis that computations required for cognitive control can occur locally in brain networks independently of the mPFC.
Excisional skin cancer surgery is a common procedure, with no formal consensus for mitigating the risk of wrong-site cutaneous surgery. To systematically consider the usefulness and feasibility of proposed methods for correct biopsy site identification in dermatology. Survey study with a formal consensus process. Item development was via a literature review and expert interviews, followed by 2 stages of a Delphi process to develop consensus recommendations. In total, 2323 articles were reviewed in the literature search, with data extraction from 14. Twenty-five experts underwent 30-minute structured interviews, which were transcribed and coded. The resulting survey was composed of 42 proposed interventions by multiple stakeholders (biopsying physicians, operating physicians, nurses, ancillary staff, patients, caregivers, and family members) at 3 time points (day of biopsy, delay and consultation period, and day of definitive surgery). Two rounds of a Delphi process with 59 experts (25 academic and 34 private practice) scored the survey. Strong consensus was obtained on 14 behaviors, and moderate consensus was obtained on 21 other behaviors. In addition, a 2-state simultaneous algorithm was developed to model surgeon behavior on the day of definitive surgery based on surgeon and patient perceptions. When definitive surgery is performed after the initial biopsy and by a different surgeon, procedures can be implemented at several time points to increase the likelihood of correct site identification. The specific circumstances of a case suggest which methods may be most appropriate and feasible, and some may be implemented. The risk of wrong-site cutaneous surgery can be reduced but not eliminated.
Abstract Cognitive control tasks require using one class of information while ignoring competing classes of information. The central role of the medial prefrontal cortex (mPFC) in cognitive control is well established in the primate literature, and largely accepted in the rodent literature because mPFC damage causes deficits in tasks that may require cognitive control, as inferred, typically from the task design. In prior work we used an active place avoidance task where a rat or mouse on a rotating arena is required to avoid the stationary task-relevant locations of a mild shock and ignore the rotating task-irrelevant locations of those shocks. The task is impaired by hippocampal manipulations, and the discharge of hippocampal place cell populations judiciously alternates between representing stationary locations near the shock zone and rotating locations far from the shock zone, demonstrating cognitive control concurrently in behavior and the hippocampal representation of spatial information. Here we test whether rat mPFC lesion impairs the active place avoidance task to evaluate two competing hypotheses, a “central-computation” hypothesis that the mPFC is essential for the computations required for cognitive control and an alternative “local-computation” hypothesis that other brain areas can perform the computations required for cognitive control, independent of mPFC. Ibotenic acid lesion of the mPFC was effective, damaging the cingulate, prelimbic and infralimbic cortices. The lesion also altered the normal coordination of metabolic activity across remaining structures. The lesion did not impair learning to avoid the initial location of shock or long-term place avoidance memory, but impaired avoidance after the shock was relocated. The lesion also did not impair the alternation between task-relevant and task-irrelevant hippocampal representations of spatial information. These findings support the local-computation hypothesis that computations required for cognitive control can occur locally in brain networks independently of the mPFC.
The genes encoding several synaptic proteins, including acetylcholine receptors, acetylcholinesterase, and the muscle-specific kinase, MuSK, are expressed selectively by a small number of myofiber nuclei positioned near the synaptic site. Genetic analysis of mutant mice suggests that additional genes, expressed selectively by synaptic nuclei, might encode muscle-derived retrograde signals that regulate the differentiation of motor axon terminals. To identify candidate retrograde signals, we used a microarray screen to identify genes that are preferentially expressed in the synaptic region of muscle, and we analyzed one such gene, CD24 , further. We show that CD24 , which encodes a small, variably and highly glycosylated, glycosylphosphatidylinositol (GPI)-linked protein, is expressed preferentially by myofiber synaptic nuclei in embryonic and adult muscle, and that CD24 expression is restricted to the central region of muscle independent of innervation. Moreover, we show that CD24 has a role in presynaptic differentiation, because synaptic transmission is depressed and fails entirely, in a cyclical manner, after repetitive stimulation of motor axons in CD24 mutant mice. These deficits in synaptic transmission, which are accompanied by aberrant stimulus-dependent uptake of AM1–43 from axons, indicate that CD24 is required for normal presynaptic maturation and function. Because CD24 is also expressed in some neurons, additional experiments will be required to determine whether pre- or postsynaptic CD24 mediates these effects on presynaptic development and function.
Abstract Thrombosis leads to ischemic organ damage in cardiovascular and thromboembolic diseases. Neutrophils promote thrombosis in vitro and in vivo by releasing neutrophil extracellular traps (NETs). NETs are composed of DNA filaments coated with histones and neutrophil enzymes such as myeloperoxidase (MPO). Circulating extracellular DNA (ceDNA) is widely used as a surrogate marker to monitor NET formation in thrombosis. This narrative review summarizes the association of ceDNA with human thrombosis. Levels of ceDNA indicate the extent and outcome of several cardiovascular and thromboembolic diseases, including myocardial infarction, stroke, and venous thromboembolism. ceDNA correlates with markers of coagulation and platelet consumption, thus supporting the hypothesis that ceDNA may be a surrogate marker of thrombus formation. In addition, ceDNA levels correlate with markers of cell injury and size of ischemic lesions, suggesting that ceDNA does not derive from NETs but is probably released from damaged organs. Few studies identified NET-specific biomarkers such as DNA–MPO complexes in the blood of patients with thrombosis. In conclusion, it remains to be established whether ceDNA in patients derives from NETs and is a cause or consequence of thrombosis.
