RdgB2 is required for dim-light input into intrinsically photosensitive retinal ganglion cells.

A subset of retinal ganglion cells is intrinsically photosensitive (ipRGCs) and contributes directly to the pupillary light reflex and circadian photoentrainment under bright-light conditions. ipRGCs are also indirectly activated by light through cellular circuits initiated in rods and cones. A mammalian homologue (RdgB2) of a phosphoinositide transfer/exchange protein that functions in Drosophila phototransduction is expressed in the retinal ganglion cell layer. This raised the possibility that RdgB2 might function in the intrinsic light response in ipRGCs, which depends on a cascade reminiscent of Drosophila phototransduction. Here we found that under high light intensities, RdgB2(-/-) mutant mice showed normal pupillary light responses and circadian photoentrainment. Consistent with this behavioral phenotype, the intrinsic light responses of ipRGCs in RdgB2(-/-) were indistinguishable from wild-type. In contrast, under low-light conditions, RdgB2(-/-) mutants displayed defects in both circadian photoentrainment and the pupillary light response. The RdgB2 protein was not expressed in ipRGCs but was in GABAergic amacrine cells, which provided inhibitory feedback onto bipolar cells. We propose that RdgB2 is required in a cellular circuit that transduces light input from rods to bipolar cells that are coupled to GABAergic amacrine cells and ultimately to ipRGCs, thereby enabling ipRGCs to respond to dim light

An interpretable imbalanced semi-supervised deep learning framework for improving differential diagnosis of skin diseases

Dermatological diseases are among the most common disorders worldwide. This paper presents the first study of the interpretability and imbalanced semi-supervised learning of the multiclass intelligent skin diagnosis framework (ISDL) using 58,457 skin images with 10,857 unlabeled samples. Pseudo-labelled samples from minority classes have a higher probability at each iteration of class-rebalancing self-training, thereby promoting the utilization of unlabeled samples to solve the class imbalance problem. Our ISDL achieved a promising performance with an accuracy of 0.979, sensitivity of 0.975, specificity of 0.973, macro-F1 score of 0.974 and area under the receiver operating characteristic curve (AUC) of 0.999 for multi-label skin disease classification. The Shapley Additive explanation (SHAP) method is combined with our ISDL to explain how the deep learning model makes predictions. This finding is consistent with the clinical diagnosis. We also proposed a sampling distribution optimisation strategy to select pseudo-labelled samples in a more effective manner using ISDLplus. Furthermore, it has the potential to relieve the pressure placed on professional doctors, as well as help with practical issues associated with a shortage of such doctors in rural areas

Evasion of anti-growth signaling: a key step in tumorigenesis and potential target for treatment and prophylaxis by natural compounds

The evasion of anti-growth signaling is an important characteristic of cancer cells. In order to continue to proliferate, cancer cells must somehow uncouple themselves from the many signals that exist to slow down cell growth. Here, we define the anti-growth signaling process, and review several important pathways involved in growth signaling: p53, phosphatase and tensin homolog (PTEN), retinoblastoma protein (Rb), Hippo, growth differentiation factor 15 (GDF15), AT-rich interactive domain 1A (ARID1A), Notch, insulin-like growth factor (IGF), and Krüppel-like factor 5 (KLF5) pathways. Aberrations in these processes in cancer cells involve mutations and thus the suppression of genes that prevent growth, as well as mutation and activation of genes involved in driving cell growth. Using these pathways as examples, we prioritize molecular targets that might be leveraged to promote anti-growth signaling in cancer cells. Interestingly, naturally-occurring phytochemicals found in human diets (either singly or as mixtures) may promote anti-growth signaling, and do so without the potentially adverse effects associated with synthetic chemicals. We review examples of naturally-occurring phytochemicals that may be applied to prevent cancer by antagonizing growth signaling, and propose one phytochemical for each pathway. These are: epigallocatechin-3-gallate (EGCG) for the Rb pathway, luteolin for p53, curcumin for PTEN, porphyrins for Hippo, genistein for GDF15, resveratrol for ARID1A, withaferin A for Notch and diguelin for the IGF1-receptor pathway. The coordination of anti-growth signaling and natural compound studies will provide insight into the future application of these compounds in the clinical setting

Mouse ganglion-cell photoreceptors are driven by the most sensitive rod pathway and by both types of cones.

Intrinsically photosensitive retinal ganglion cells (iprgcs) are depolarized by light by two mechanisms: directly, through activation of their photopigment melanopsin; and indirectly through synaptic circuits driven by rods and cones. To learn more about the rod and cone circuits driving ipRGCs, we made multielectrode array (MEA) and patch-clamp recordings in wildtype and genetically modified mice. Rod-driven ON inputs to ipRGCs proved to be as sensitive as any reaching the conventional ganglion cells. These signals presumably pass in part through the primary rod pathway, involving rod bipolar cells and AII amacrine cells coupled to ON cone bipolar cells through gap junctions. Consistent with this interpretation, the sensitive rod ON input to ipRGCs was eliminated by pharmacological or genetic disruption of gap junctions, as previously reported for conventional ganglion cells. A presumptive cone input was also detectable as a brisk, synaptically mediated ON response that persisted after disruption of rod ON pathways. This was roughly three log units less sensitive than the rod input. Spectral analysis revealed that both types of cones, the M- and S-cones, contribute to this response and that both cone types drive ON responses. This contrasts with the blue-OFF, yellow-ON chromatic opponency reported in primate ipRGCs. The cone-mediated response was surprisingly persistent during steady illumination, echoing the tonic nature of both the rod input to ipRGCs and their intrinsic, melanopsin-based phototransduction. These synaptic inputs greatly expand the dynamic range and spectral bandpass of the non-image-forming visual functions for which ipRGCs provide the principal retinal input

ipRGCs with distinct types of intrinsic light response exhibit similar synaptically driven photoresponses.

<p>Upper panel: raster plots of two representative ipRGCs with distinct kinetics of melanopsin-driven intrinsic photoresponse, apparently corresponding to two types defined by Tu et al., (2005) in adult mice. Type II cell (blue) has long onset latency and shorter post-stimulus discharge; Type III has short latency and prolonged afterdischarge. Stimulus was a 60 sec light step (yellow bar; 480 nm, ∼6×10¹² photons/cm²·s). Recordings were performed under synaptic blockade. Lower panel: intensity-response series of the same two cells, but without synaptic blockade. The light stimuli were one second flashes 500 nm flashes ascending in intensity within the series. Both cells showed the same irradiance-response properties, with thresholds approximately 0.02 Rh*/rod/s.</p

Light-evoked synaptic inputs to ipRGCs are less sensitive in Cx36 knockout mice.

<p><b><i>A</i></b>: Raster displays comparing responses of a single representative ipRGC in a Cx36 knockout mouse (right column) with those of an ipRGC in a wildtype littermate (left column). Responses of each cell are shown for a series of 500 nm flashes of increasing intensity. The dimmest stimulus evoking a clear response was approximately three log units higher in the Cx36 KO mouse (∼22.7 Rh^*/rod/s) than it was in the wildtype control (0.02 Rh*/rod/s; see also the data for the C57Bl76 control mice; Fig. 2). <b><i>B</i></b>: Group data comparing irradiance-response curves for ipRGCs recorded in the Cx36 knockout (black squares; n = 31) and wildtype animals (open squares; n = 24). Data come from 4 pairs of littermates consisting of one wildtype and one knockout animal. The triangles near the abscissa indicate the response thresholds (5% of maximum; open triangle, Cx36^+/+; filled triangle, Cx36^−/−), which are about 3 orders of magnitude higher in the knockouts than in the wildtype mice. This reduction in sensitivity presumably reflects the loss of input from the primary rod pathway.</p

Input from the most sensitive rod pathway to ipRGCs.

<p><b><b><i>A</i></b><b>:</b></b> Raster plots of synaptically driven spike responses of a single typical ipRGC in response to a series of flashes increasing in intensity (500 nm; 1 sec). Recordings were extracellular, obtained on a multielectrode array in a dark-adapted wildtype (C57Bl6) mouse retina. <b><i>B</i></b>: Irradiance-response curve plotted in semi-log coordinates and based on data averaged from 23 wildtype mouse ipRGCs. For each cell, response amplitude at a given intensity was expressed as the firing rate during that stimulus normalized to the maximal light-evoked firing rate at any intensity. These values were averaged across all cells for each intensity and plotted, with error bars representing the standard error of the mean. The smooth curve represents the Michaelis-Menten fit to these points and the single triangle along the abscissa indicates the response threshold (5% of maximum, calculated from the fit). This irradiance-response profile closely resembles those of ON type RGCs receiving input from the primary rod pathway <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066480#pone.0066480-Volgyi1" target="_blank">[50]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066480#pone.0066480-Deans2" target="_blank">[51]</a>. <b><i>C</i></b>: Distribution of the thresholds of the ON responses in ipRGCs (left; n = 8) in comparison with those of non-ipRGCs (right; n = 22) recorded in the same piece of retina. The thresholds of ipRGCs all located in the lower part of this plot, indicating they are among the most light-sensitive mouse RGCs.</p

Evidence for ON channel input to ipRGCs from both M-cones and S-cones.

<p><b>A</b>, <b>B</b>: Raster plots of responses to spectrally narrowband stimuli for ten ipRGCs recorded simultaneously in a Cx36 knockout mouse retina. These brisk ON responses were presumably exclusively cone-driven because Cx36 KO mice lack the primary and secondary rod ON pathways and because the flashes were subthreshold for activation by intrinsic melanopsin phototransduction. The response to a 400 nm stimulus (A) closely resembled that to a 500 nm stimulus (B), despite the fact that the former would be more effective in stimulating S-cones and the latter much more effective for M-cones. The two stimuli were approximately matched for photon flux density (400 nm: ∼5×10¹¹ photons cm⁻² s⁻¹; 500 nm: ∼7×10¹¹ photons cm⁻² s⁻¹). <b>C</b>: synaptic blockade eliminated these responses (in this case, the 400 nm response), confirming their origin in the outer retina. <b>D</b>: intrinsic, melanopsin-driven responses revealed in the same cells under synaptic blockade by increasing the intensity, spectral bandwidth and duration of the light. <b>E</b>, <b>F</b>: Group data summarizing the irradiance-response behavior at 400nm and 500nm for these cells (n  =  10), with response amplitudes measured either in terms of the number of evoked spikes (E) or the mean firing rate during the stimulus (F). The curves for the two wavelengths are nearly identical. This is inconsistent with a pure M-cone input, which would predict sensitivity at 500 nm ∼1 log unit greater than that at 400 nm. It is also inconsistent with a pure S-cone input, which would predict >4 log unit greater sensitivity at 400 nm than at 500 nm. We confirmed in a larger sample (25 ipRGCs from three Cx36 KO retinas) that 400nm and 500nm stimuli of matched irradiance evoked comparable responses. <b>G</b>: Whole-cell voltage clamp recordings from a representative example of an M1 cell (top panels) and an M2 cell (bottom panels) from the dorsal retina, where middle and long-wavelength cone opsins are expressed in distinct cone types. Responses are shown to a 1 s step of 360 nm (left) or 500 nm (right) light (horizontal black line). Different colored traces represent responses to different light intensities (in photons•cm⁻²•s⁻¹) for the M1 cell: 3×10¹¹−2×10¹⁴ (360 nm) and 2×10¹²−6×10¹⁴ (500 nm); and for the M2 cell: 7×10¹⁰−5×10¹³ (360 nm) and 1×10¹¹−2×10¹⁴ (500 nm). Similar results were obtained in all M1 and M2 cells recorded, whether in the dorsal retina (six M2 cells and one M1 cell) or the ventral retina (four M2 cells and one M1 cell).</p

High-threshold light-evoked synaptic responses survive interruption of primary and secondary rod pathways by Cx36 knockout.

<p><b><i>A</i></b>: Raster plots of light responses in a representative ipRGC from a Cx36 KO mouse recorded first with synapses functional (left) and then with synapses blocked (right). In synaptic blockade, the light response exhibited the long latency and prominent poststimulus persistence of spiking characteristic of melanopsin-mediated responses. With synaptic input intact (left), responses were brisker and more sensitive than the melanopsin-driven response. Because both primary and secondary rod ON pathways were disrupted by the genetic deletion of Cx36, these brisk, synaptically mediated responses were presumably driven by cones. Note that stimulus intensities are not matched in the left and right columns of panel A. Also, stimulus duration was increased 10-fold under synaptic blockade (right) because a 1 sec stimulus was too short to evoke an intrinsic photoresponse at most intensities tested. <b><i>B</i></b>: Group irradiance-response data of the sort illustrated in panel A for ten ipRGCs recorded from the same piece of Cx36 KO mouse retina. The triangles along the abscissa indicate the response thresholds (5% of maximum; open triangle, synapses functional; filled triangle, synapses blocked). The presumptive cone-driven response is at least 2 log units more sensitive than the melanopsin drive; the difference would have been greater if stimulus duration had not been increased under synaptic blockade to enhance the intrinsic response. Qualitatively similar results were obtained in a total of 8 retinas (data not shown).</p