Melanosome degradation: fact or fiction

Our mini review summarizes what is known about the (bio)degradation of melanosomes. Unlike melanosome biogenesis where our knowledge enables us to explain it in molecular terms posing many interesting questions on the relation between lysosomes and melanosomes, melanosome degradation has remained 'terra incognita'. Observations at optical and ultrastructural levels describe the disintegration of melanosomes in the lysosomal compartment (in auto- and heterophagosomes). Histochemical studies suggest the participation of acid hydrolases in the process of melanosome degradation. Biochemical data confirm the ability of lysosomal hydrolases to degrade melanosome constituents except the melanin moiety. The similarity of melanin structure to that of polycyclic aromatic hydrocarbons suggests that melanin should be sensitive mainly, if not exclusively, to oxidative breakdown. In vitro melanin can indeed be decomposed by an oxidative attack and the degradation is accompanied by fluorescence and decreasing absorbance. From enzymes engaged in the biotransformation of polycyclic hydrocarbons only phagosomal NADPH oxidase meets the criteria (particularly as for compartmental and catalytic properties) to be involved in melanin biodegradation. The in vivo biodegradation of melanin has so far been clearly demonstrated in Aspergillus and fungi melanins.     

Integrating social science and genetics: news from the political front

There has been growing interest in the use of genetic models to expand the understanding of political preferences, attitudes, and behaviors. Researchers in the social sciences have begun incorporating these models and have revealed that genetic differences account for individual differences in political beliefs, behaviors, and responses to the political environment. The first Integrating Genetics and the Social Sciences Conference, held at Boulder, Colorado in May of 2010, brought together these researchers. As a result, we jointly review the last 5 years of research in this area. In doing so, we explicate the methods, findings, and limitations of behavior genetic approaches, including twin designs, association studies, and genome-wide analyses, in their application toward exploring political preferences.     

Organ printing: fiction or science

Aggregates of living cells (i.e. model tissue fragments) under appropriate conditions fuse like liquid drops. According to Steinberg's differential adhesion hypothesis (DAH), this may be understood by assuming that cells are motile and tissues made of such cells possess an effective surface tension. Here we show that based on these properties three-dimensional cellular structures of prescribed shape can be constructed by a novel method: cell aggregate printing. Spherical aggregates of similar size made of cells with known adhesive properties were prepared. Aggregates were embedded into biocompatible gels. When the cellular and gel properties, as well as the symmetry of the initial configuration were appropriately adjusted the contiguous aggregates fused into ring-like organ structures. To elucidate the driving force and optimal conditions for this pattern formation, Monte Carlo simulations based on a DAH motivated model were performed. The simulations reproduced the experimentally observed cellular arrangements and revealed that the control parameter of pattern evolution is the gel-tissue interfacial tension, an experimentally accessible parameter.