Chk2 and p53 Are Haploinsufficient with Dependent and Independent Functions to Eliminate Cells after Telomere Loss

The mechanisms that cells use to monitor telomere integrity, and the array of responses that may be induced, are not fully defined. To date there have been no studies in animals describing the ability of cells to survive and contribute to adult organs following telomere loss. We developed assays to monitor the ability of somatic cells to proliferate and differentiate after telomere loss. Here we show that p53 and Chk2 limit the growth and differentiation of cells that lose a telomere. Furthermore, our results show that two copies of the genes encoding p53 and Chk2 are required for the cell to mount a rapid wildtype response to a missing telomere. Finally, our results show that, while Chk2 functions by activating the p53-dependent apoptotic cascade, Chk2 also functions independently of p53 to limit survival. In spite of these mechanisms to eliminate cells that have lost a telomere, we find that such cells can make a substantial contribution to differentiated adult tissues

Evidence for distributed light sensing in the skin of cuttlefish, Sepia officinalis

We report that the skin of cuttlefish, Sepia officinalis, contains opsin transcripts suggesting a possible role of distributed light sensing for dynamic camouflage and signalling. The mRNA coding for opsin from various body regions was amplified and sequenced, and gene expression was detected in fin and ventral skin samples. The amino acid sequence of the opsin polypeptide that these transcripts would produce was identical in retina and fin tissue samples, but the ventral skin opsin transcripts differed by a single amino acid. The diverse camouflage and signalling body patterns of cephalopods are visually controlled, and these findings suggest a possible additional mechanism of light sensing and subsequent skin patterning. Cuttlefish, along with a number of other cephalopod species, have been shown to be colour-blind. Since the opsin in the fin is identical to that of the retina (λmax = 492 nm), and the ventral transcripts are also unlikely to be spectrally different, colour discrimination by the skin opsins is unlikely. However, spectral discrimination could be provided by involving other skin structures (chromatophores and iridophores), which produce changeable colours and patterns. This ‘distributed sensing’ could supplement the otherwise visually driven dynamic camouflage system by assisting with colour or brightness matching to adjacent substrates

Inversion by P4: polarization-picture post-processing

Polarization may be sensed by imaging modules. This is done in various engineering systems as well as in biological systems, specifically by insects and some marine species. However, polarization per pixel is usually not the direct variable of interest. Rather, polarization-related data serve as a cue for recovering task-specific scene information. How should polarization-picture post-processing (P4) be done for the best scene understanding? Answering this question is not only helpful for advanced engineering (computer vision), but also to prompt hypotheses as to the processing occurring within biological systems. In various important cases, the answer is found by a principled expression of scene recovery as an inverse problem. Such an expression relies directly on a physics-based model of effects in the scene. The model includes analysis that depends on the different polarization components, thus facilitating the use of these components during the inversion, in a proper, even if non-trivial, manner. We describe several examples for this approach. These include automatic removal of path radiance in haze or underwater, overcoming partial semireflections and visual reverberations; three-dimensional recovery and distance-adaptive denoising. The resulting inversion algorithms rely on signal-processing methods, such as independent component analysis, deconvolution and optimization