Validity of Xiphophorus fish as models for human disease.

Platyfish and swordtails of the genus Xiphophorus provide a well-established model for melanoma research and have become well known for this feature. Recently, modelling approaches for other human diseases in Xiphophorus have been developed or are emerging. This Review provides a comprehensive summary of these models and discusses how findings from basic biological and molecular studies and their translation to medical research demonstrate that Xiphophorus models have face, construct and predictive validity for studying a broad array of human diseases. These models can thus improve our understanding of disease mechanisms to benefit patients.

The cellular slime mold Fonticula alba forms a dynamic, multicellular collective while feeding on bacteria.

Multicellularity evolved in fungi and animals, or the opisthokonts, from their common amoeboflagellate ancestor but resulted in strikingly distinct cellular organizations. The origins of this multicellularity divergence are not known. The stark mechanistic differences that underlie the two groups and the lack of information about ancestral cellular organizations limits progress in this field. We discovered a new type of invasive multicellular behavior in Fonticula alba, a unique species in the opisthokont tree, which has a simple, bacteria-feeding sorocarpic amoeba lifestyle. This invasive multicellularity follows germination dependent on the bacterial culture state, after which amoebae coalesce to form dynamic collectives that invade virgin bacterial resources. This bacteria-dependent social behavior emerges from amoeba density and allows for rapid and directed invasion. The motile collectives have animal-like properties but also hyphal-like search and invasive behavior. These surprising findings enrich the diverse multicellularities present within the opisthokont lineage and offer a new perspective on fungal origins.

Schmidtea happens: Re-establishing the planarian as a model for studying the mechanisms of regeneration.

Understanding the remarkable regenerative abilities of freshwater planarians was a classic problem of developmental biology. These animals were widely studied until the late 1960s, when their use as experimental subjects declined precipitously after some infamous experiments on memory transfer. By the mid-1990s, only a handful of laboratories worldwide were investigating the mechanisms of planarian regeneration. Here, we provide the personal stories behind our work to reinvigorate studies of these fascinating animals. We recount many of the challenges that had to be overcome and reflect on some of the fortuitous events that helped launch the planarian Schmidtea mediterranea as a model organism for studying the molecular basis of regeneration.

The good, the bad, and the ugly: From planarians to parasites.

Platyhelminthes can perhaps rightly be described as a phylum of the good, the bad, and the ugly: remarkable free-living worms that colonize land, river, and sea, which are often rife with color and can display extraordinary regenerative ability; parasitic worms like schistosomes that cause devastating disease and suffering; and monstrous tapeworms that are the stuff of nightmares. In this chapter, we will explore how our research expanded beyond free-living planarians to their gruesome parasitic cousins. We start with Schistosoma mansoni, which is not a new model; however, approaching these parasites from a developmental perspective required a reinvention that may hold generalizable lessons to basic biologists interested in pivoting to disease models. We then turn to our (re)establishment of the rat tapeworm Hymenolepis diminuta, a once-favorite model that had been largely forgotten by the molecular biology revolution. Here we tell our stories in three, first-person narratives in order to convey personal views of our experiences. Welcome to the dark side.

Periodic patterns in Rodentia: Development and evolution.

Mammalian periodic pigment patterns, such as spots and stripes, have long interested mathematicians and biologists because they arise from non-random developmental processes that are programmed to be spatially constrained, and can therefore be used as a model to understand how organized morphological structures develop. Despite such interest, the developmental and molecular processes underlying their formation remain poorly understood. Here, we argue that Arvicanthines, a clade of African rodents that naturally evolved a remarkable array of coat patterns, represent a tractable model system in which to dissect the mechanistic basis of pigment pattern formation. Indeed, we review recent insights into the process of stripe formation that were obtained using an Arvicanthine species, the African striped mouse (Rhabdomys pumilio), and discuss how these rodents can be used to probe deeply into our understanding of the factors that specify and implement positional information in the skin. By combining naturally evolved pigment pattern variation in rodents with classic and novel experimental approaches, we can substantially advance our understanding of the processes by which spatial patterns of cell differentiation are established during embryogenesis, a fundamental question in developmental biology.

An endogenous explanation of growth: direct-to-consumer stem cell therapies in PR China, India and the USA.

The recent expansion of direct-to-consumer stem cell therapies (DSCTs) across nations where medical malpractice laws are the strongest globally challenges the causal assumption that low regulatory standards in developing countries bolster DSCTs. Drawing on firm-level data of existing biopharmaceuticals, approved stem cell therapies (SCTs) and DSCT clinics across the USA, PR China and India, this paper provides an innovation studies perspective of the ways in which the paradigmatic shift in fundamental knowledge production - from in vitro to in vivo stem cells - is transforming SCT discovery and delivery. It argues that the endogenous and inherent disruptive attributes of SCTs, rather than exogenous conditions like regulations, provide a substantive explanation for the recent expansion of DSCTs and urges regulatory adaptation to endogenous imperatives for effective governance of SCTs.