Evolution of cichlid vision via trans-regulatory divergence.

BACKGROUND: Phenotypic evolution may occur through mutations that affect either the structure or expression of protein-coding genes. Although the evolution of color vision has historically been attributed to structural mutations within the opsin genes, recent research has shown that opsin regulatory mutations can also tune photoreceptor sensitivity and color vision. Visual sensitivity in African cichlid fishes varies as a result of the differential expression of seven opsin genes. We crossed cichlid species that express different opsin gene sets and scanned their genome for expression Quantitative Trait Loci (eQTL) responsible for these differences. Our results shed light on the role that different structural, cis-, and trans-regulatory mutations play in the evolution of color vision. RESULTS: We identified 11 eQTL that contribute to the divergent expression of five opsin genes. On three linkage groups, several eQTL formed regulatory "hotspots" associated with the expression of multiple opsins. Importantly, however, the majority of the eQTL we identified (8/11 or 73%) occur on linkage groups located trans to the opsin genes, suggesting that cichlid color vision has evolved primarily via trans-regulatory divergence. By modeling the impact of just two of these trans-regulatory eQTL, we show that opsin regulatory mutations can alter cichlid photoreceptor sensitivity and color vision at least as much as opsin structural mutations can. CONCLUSIONS: Combined with previous work, we demonstrate that the evolution of cichlid color vision results from the interplay of structural, cis-, and especially trans-regulatory loci. Although there are numerous examples of structural and cis-regulatory mutations that contribute to phenotypic evolution, our results suggest that trans-regulatory mutations could contribute to phenotypic divergence more commonly than previously expected, especially in systems like color vision, where compensatory changes in the expression of multiple genes are required in order to produce functional phenotypes.

Hyperspectral imaging: a non-invasive method of imaging melanoma lesions in a patient with stage IV melanoma, being treated with a RAF inhibitor.

Utilizing a macroscopic Prism and Reflectance Imaging Spectroscopy System (MACRO-PARISS), spectral data are taken from human skin using a fiber optic light probe. The subject was an oncology patient at the University of Pennsylvania, with biopsy proven melanoma, who underwent chemotherapy with a novel small molecule BRAF inhibitor as part of a Phase I clinical trial. The BRAF mutation had been previously identified in this patient. Cutaneous lesions were identified by a clinical oncologist, and lesions were imaged periodically over a 1 month period of time. Spectra are classified using a linearity-independent algorithm over a wavelength range of 450-920 nm. Spectral signatures, or characteristic features, of generated spectra correlate with gross features of lesions that are readily observable. Using PARISS we demonstrated differences between spectral signatures of treated lesions over a treatment course, indicating spectral data correlation with changes in disease. PARISS may be useful to better establish a noninvasive means of following disease progression, and ultimately establish characteristic spectral signatures to define disease presence in the future.