Genetics of melanoma predisposition

Predisposition to melanoma is genetically heterogeneous. Two high penetrance susceptibility genes, CDKN2A and CDK4, have so far been identified and mapping is ongoing to localize and identify others. With the advent of a catalogue of millions of potential DNA polymorphisms, attention is now also being focused on identification of genes that confer a more modest contribution to melanoma risk, such as those encoding proteins involved in pigmentation, DNA repair, cell growth and differentiation or detoxification of metabolites. One such pigmentation gene, MC1R, has not only been found to be a low penetrance melanoma gene but has also been shown to act as a genetic modifier of melanoma risk in individuals carrying CDKN2A mutations. Most recently, an environmental agent, ultraviolet radiation, has also been established as a modifier of melanoma risk in CDKN2A mutation carriers. Hence, melanoma is turning out to be an excellent paradigm for studying gene-gene and gene-environment interactions.

Making developmental biology relevant to undergraduates in an era of economic rationalism in Australia

This report describes the road map we followed at our university to accommodate three main factors: financial pressure within the university system; desire to enhance the learning experience of undergraduates; and motivation to increase the prominence of the discipline of developmental biology in our university. We engineered a novel, multi-year undergraduate developmental biology program which was student-oriented, ensuring that students were continually exposed to the underlying principles and philosophy of this discipline throughout their undergraduate career. Among its key features are introductory lectures in core courses in the first year, which emphasize the relevance of developmental biology to tissue engineering, reproductive medicine, therapeutic approaches in medicine, agriculture and aquaculture. State-of-the-art animated computer graphics and images of high visual impact are also used. In addition, students are streamed into the developmental biology track in the second year, using courses like human embryology and courses shared with cell biology, which include practicals based on modern experimental approaches. Finally, fully dedicated third-year courses in developmental biology are undertaken in conjunction with stand-alone practical courses where students experience first-hand work in a research laboratory. Our philosophy is a cradle-to-grave approach to the education of undergraduates so as to prepare highly motivated, enthusiastic and well-educated developmental biologists for entry into graduate programs and ultimately post-doctoral research.

Visual Biology of Hawaiian Coral Reef Fishes. III. Environmental Light and an Integrated Approach to the Ecology of Reef Fish Vision

In the previous two papers in this three-part series, we have examined visual pigments, ocular media transmission, and colors of the coral reef fish of Hawaii. This paper first details aspects of the light field and background colors at the microhabitat level on Hawaiian reefs and does so from the perspective and scale of fish living on the reef. Second, information from all three papers is combined in an attempt to examine trends in the visual ecology of reef inhabitants. Our goal is to begin to see fish the way they appear to other fish. Observations resulting from the combination of results in all three papers include the following. Yellow and blue colors on their own are strikingly well matched to backgrounds on the reef such as coral and bodies of horizontally viewed water. These colors, therefore, depending on context, may be important in camouflage as well as conspicuousness. The spectral characteristics of fish colors are correlated to the known spectral sensitivities in reef fish single cones and are tuned for maximum signal reliability when viewed against known backgrounds. The optimal positions of spectral sensitivity in a modeled dichromatic visual system are generally close to the sensitivities known for reef fish. Models also predict that both UV-sensitive and red-sensitive cone types are advantageous for a variety of tasks. UV-sensitive cones are known in some reef fish, red-sensitive cones have yet to be found. Labroid colors, which appear green or blue to us, may he matched to the far-red component of chlorophyll reflectance for camouflage. Red cave/hole dwelling reef fish are relatively poorly matched to the background they are often viewed against but this may be visually irrelevant. The model predicts that the task of distinguishing green algae from coral is optimized with a relatively long wavelength visual pigment pair. Herbivorous grazers whose visual pigments are known possess the longest sensitivities so far found. Labroid complex colors are highly contrasting complementary colors close up but combine, because of the spatial addition, which results from low visual resolution, at distance, to match background water colors remarkably well. Therefore, they are effective for simultaneous communication and camouflage.

Visual Biology of Hawaiian Coral Reef Fishes. I. Ocular Transmission and Visual Pigments

The visual biology of Hawaiian reef fishes was explored by examining their eyes for spectral sensitivity of their visual pigments and for transmission of light through the ocular media to the retina. The spectral absorption curves for the visual pigments of 38 species of Hawaiian fish were recorded using microspectrophotometry. The peak absorption wavelength (lambda(max)) of the rods varied from 477-502 nm and the lambda(max) of individual species conformed closely to values for the same species previously reported using a whole retina extraction procedure. The visual pigments of single cone photoreceptors were categorized, dependent on their lambda(max)-values, as ultraviolet (347-376 nm), violet (398-431 nm) or blue (439-498 nm) sensitive cones. Eight species possessed ultraviolet-sensitive cones and 14 species violet-sensitive cones. Thus, 47% of the species examined displayed photosensitivity to the short-wavelength region of the spectrum. Both identical and nonidentical paired and double cones were found with blue sensitivity or green absorption peaks (> 500 nm). Spectrophotometry of the lens, cornea, and humors for 195 species from 49 families found that the spectral composition of the light transmitted to the retina was most often limited by the lens (73% of species examined). Except for two unusual species with humor-limited eyes, Acanthocybium solandri (Scombridae) and the priacanthid fish, Heteropriacanthus cruentatus, the remainder had corneal-limited eyes. The wavelength at which 50% of the light was blocked (T50) was classified according to a system modified from Douglas and McGuigan (1989) as Type I, T50 < = 355 nm, (32 species); Type IIa, 355 < T50 < = 380 nm (30 species); Type IIb, 380 < T50 405 nm (84 species). Possession of UV-transmitting ocular media follows both taxonomic and functional lines and, if the ecology of the species is considered, is correlated with the short-wavelength visual pigments found in the species. Three types of short-wavelength vision in fishes are hypothesized: UV-sensitive, UV-specialized, and violet-specialized. UV-sensitive eyes lack UV blockers (Type I and IIa) and can sense UV light with the secondary absorption peak or beta peak of their longer wavelength visual pigments but do not possess specialized UV receptor cells and, therefore, probably lack UV hue discrimination. UV-specialized eyes allow transmission of UV light to the retina (Type I and IIa) and also possess UV-sensitive cone receptors with peak absorption between 300 and 400 nm. Given the appropriate perceptual mechanisms, these species could possess true UV-color vision and hue discrimination. Violet-specialized eyes extend into Type IIb eyes and possess violet-sensitive cone cells. UV-sensitive eyes are found throughout the fishes from at least two species of sharks to modern bony fishes. Eyes with specialized short-wavelength sensitivity are common in tropical reef fishes and must be taken into consideration when performing research involving the visual perception systems of these fishes. Because most glass and plastics are UV-opaque, great care must be taken to ensure that aquarium dividers, specimen holding containers, etc., are UV-transparent or at least to report the types of materials in use.

Faeces as a source of DNA for molecular studies in a threatened population of great bustards

With recent advances in molecular biology, it is now possible to use the trace amounts of DNA in faeces to non-invasively sample endangered species for genetic studies. A highly vulnerable population of approximately 100 great bustards (Otis tarda) exists in Morocco necessitating the use of non-invasive protocols to study their genetic structure. Here we report a reliable silica-based method to extract DNA from great bustard faeces. We found that successful extraction and amplification correlated strongly with faeces freshness and composition. We could not extract amplifiable DNA from 30% of our samples as they were dry or contained insect material. However 100% of our fresh faecal samples containing no obvious insect material worked, allowing us to assess the levels of genetic variation among 25 individuals using a 542 bp control region sequence. We were able to extract DNA from four out of five other avian species, demonstrating that faeces represents a suitable source of DNA for population genetics studies in a broad range of species.