A screen of kinase inhibitors reveals a potential role of Chk1 in regulating Hydra head regeneration and maintenance.

The cnidarian Hydra possesses remarkable regenerative capabilities which allow it to regrow lost or damaged body parts in a matter of days. Given that many key regulators of regeneration and development are evolutionarily conserved, Hydra is a valuable model system for studying the fundamental molecular mechanisms underlying these processes. In the past, kinase inhibitors have been useful tools for determining the role of conserved signaling pathways in Hydra regeneration and patterning. Here, we present a systematic screen of a commercially available panel of kinase inhibitors for their effects on Hydra regeneration. Isolated Hydra gastric segments were exposed to 5 µM of each kinase inhibitor and regeneration of the head and foot regions were scored over a period of 96 hours. Of the 80 kinase inhibitors tested, 28 compounds resulted in abnormal regeneration. We directed our focus to the checkpoint kinase 1 (Chk1) inhibitor, SB 218078, considering the role of Chk1 in G2 checkpoint regulation and the importance of G2-paused cells in Hydra regeneration. We found that Hydra exposed to SB 218078 were unable to regenerate the head and maintain head-specific structures. Furthermore, SB 218078-treated Hydra displayed a reduction in the relative proportion of epithelial cells; however, no differences were seen for interstitial stem cells or their derivatives. Lastly, exposure to SB 218078 appeared to have no impact on the level of mitosis or apoptosis. Overall, our study demonstrates the feasibility of kinase inhibitor screens for studying Hydra regeneration processes and highlights the possible role for Hydra Chk1 in head regeneration and maintenance.

Evaluating tank acclimation and trial length for dynamic shuttle box temperature preference assays in aquatic animals.

Characterizing the thermal preference of fish is important in conservation, environmental and evolutionary physiology and can be determined using a shuttle box system. Initial tank acclimation and trial lengths are important considerations in experimental design, yet systematic studies of these factors are missing. Three different behavioral assay experimental designs were tested to determine the effect of tank acclimation and trial length (hours of tank acclimation:behavioral trial: 12:12, 0:12, 2:2) on the temperature preference of juvenile lake whitefish (Coregonus clupeaformis), using a shuttle box. Average temperature preferences for the 12 h:12 h, 0 h:12 h, 2 h:2 h experimental designs were 16.10±1.07°C, 16.02±1.56°C and 16.12±1.59°C respectively, with no significant differences between experimental designs (P=0.9337). Ultimately, length of acclimation time and trial length had no significant effect on thermal preference.

The round goby genome provides insights into mechanisms that may facilitate biological invasions.

BACKGROUND: The invasive benthic round goby (Neogobius melanostomus) is the most successful temperate invasive fish and has spread in aquatic ecosystems on both sides of the Atlantic. Invasive species constitute powerful in situ experimental systems to study fast adaptation and directional selection on short ecological timescales and present promising case studies to understand factors involved the impressive ability of some species to colonize novel environments. We seize the unique opportunity presented by the round goby invasion to study genomic substrates potentially involved in colonization success. RESULTS: We report a highly contiguous long-read-based genome and analyze gene families that we hypothesize to relate to the ability of these fish to deal with novel environments. The analyses provide novel insights from the large evolutionary scale to the small species-specific scale. We describe expansions in specific cytochrome P450 enzymes, a remarkably diverse innate immune system, an ancient duplication in red light vision accompanied by red skin fluorescence, evolutionary patterns of epigenetic regulators, and the presence of osmoregulatory genes that may have contributed to the round goby's capacity to invade cold and salty waters. A recurring theme across all analyzed gene families is gene expansions. CONCLUSIONS: The expanded innate immune system of round goby may potentially contribute to its ability to colonize novel areas. Since other gene families also feature copy number expansions in the round goby, and since other Gobiidae also feature fascinating environmental adaptations and are excellent colonizers, further long-read genome approaches across the goby family may reveal whether gene copy number expansions are more generally related to the ability to conquer new habitats in Gobiidae or in fish.