A subpopulation of astrocyte progenitors defined by Sonic hedgehog signaling

Background The molecular signaling pathway, Sonic hedgehog (Shh), is critical for the proper development of the central nervous system. The requirement for Shh signaling in neuronal and oligodendrocyte development in the developing embryo are well established. However, Shh activity is found in discrete subpopulations of astrocytes in the postnatal and adult brain. Whether Shh signaling plays a role in astrocyte development is not well understood. Methods Here, we use a genetic inducible fate mapping approach to mark and follow a population of glial progenitor cells expressing the Shh target gene, Gli1, in the neonatal and postnatal brain. Results In the neonatal brain, Gli1-expressing cells are found in the dorsolateral corner of the subventricular zone (SVZ), a germinal zone harboring astrocyte progenitor cells. Our data show that these cells give rise to half of the cortical astrocyte population, demonstrating their substantial contribution to the cellular composition of the cortex. Further, these data suggest that the cortex harbors astrocytes from different lineages. Gli1 lineage astrocytes are distributed across all cortical layers, positioning them for broad influence over cortical circuits. Finally, we show that Shh activity recurs in mature astrocytes in a lineage-independent manner, suggesting cell-type dependent roles of the pathway in driving astrocyte development and function. Conclusion These data identify a novel role for Shh signaling in cortical astrocyte development and support a growing body of evidence pointing to astrocyte heterogeneity.

cdon and boc affect trunk neural crest cell migration through a non-cell autonomous reduction of hedgehog signaling in zebrafish slow-twitch muscle

The immunoglobin superfamily members cdon and boc are transmembrane proteins implicated in regulating hedgehog signaling during vertebrate development. Recent work showing roles for these genes in axon guidance and neural crest cell migration further suggest that cdon/boc may play additional functions in regulating directed cell movements during development. Here we use novel and existing mutants to investigate a role for cdon and boc in zebrafish neural crest cell migration. We find that single cdon or boc mutant embryos exhibit normal neural crest phenotypes, but that neural crest migration is strikingly disrupted in double cdon/boc mutant embryos. We further show that this neural crest migration phenotype is associated with defects to the differentiation of slow-twitch muscle cells, and that this slow-twitch muscle phenotype is a consequence of reduced hedgehog signaling in mutant fish. While neural crest migratory ability is not affected in double mutant embryos, neural crest directionality is severely affected. These data suggest that neural crest migration defects are likely to be secondary to defects in slow-twitch muscle differentiation. Combined, our data add to a growing literature showing that cdon and boc act synergistically to promote hedgehog signaling during vertebrate development, and provide a foundation for using zebrafish to further study the function of these hedgehog receptor paralogs.

Sea Anemones Responding to Sex Hormones, Oxybenzone, and Benzyl Butyl Phthalate: Transcriptional Profiling and in Silico Modelling Provide Clues to Decipher Endocrine Disruption in Cnidarians

Endocrine disruption is suspected in cnidarians, but questions remain how occurs. Steroid sex hormones are detected in corals and sea anemones even though these animals do not have estrogen receptors and their repertoire of steroidogenic enzymes appears to be incomplete. Pathways associated with sex hormone biosynthesis and sterol signaling are an understudied area in cnidarian biology. The objective of this study was to identify a suite of genes that can be linked to exposure of endocrine disruptors. Exaiptasia diaphana were exposed to nominal 20ppb concentrations of estradiol (E2), testosterone (T), cholesterol, oxybenzone (BP-3), or benzyl butyl phthalate (BBP) for 4 h. Eleven genes of interest (GOIs) were chosen from a previously generated EST library. The GOIs are 17β-hydroxysteroid dehydrogenases type 14 (17β HSD14) and type 12 (17β HSD12), Niemann-Pick C type 2 (NPC2), Equistatin (EI), Complement component C3 (C3), Cathepsin L (CTSL), Patched domain-containing protein 3 (PTCH3), Smoothened (SMO), Desert Hedgehog (DHH), Zinc finger protein GLI2 (GLI2), and Vitellogenin (VTG). These GOIs were selected because of functional associations with steroid hormone biosynthesis; cholesterol binding/transport; immunity; phagocytosis; or Hedgehog signaling. Quantitative Real-Time PCR quantified expression of GOIs. In silico modelling utilized protein structures from Protein Data Bank as well as creating protein structures with SWISS-MODEL. Results show transcription of steroidogenic enzymes, and cholesterol binding/transport proteins have similar transcription profiles for E2, T, and cholesterol treatments, but different profiles when BP-3 or BBP is present. C3 expression can differentiate between exposures to BP-3 versus BBP as well as exposure to cholesterol versus sex hormones. In silico modelling revealed all ligands (E2, T, cholesterol, BBP, and BP-3) have favorable binding affinities with 17β HSD14, 17β HSD12, NPC2, SMO, and PTCH proteins. VTG expression was down-regulated in the sterol treatments but up-regulated in BP-3 and BBP treatments. In summary, these eleven GOIs collectively generate unique transcriptional profiles capable of discriminating between the five chemical exposures used in this investigation. This suite of GOIs are candidate biomarkers for detecting transcriptional changes in steroidogenesis, gametogenesis, sterol transport, and Hedgehog signaling. Detection of disruptions in these pathways offers new insight into endocrine disruption in cnidarians.

The Effects of Hedgehog Signaling Pathway on the Proliferation and Apoptosis of Melanoma Cells

Background. Studies have found that the abnormality of the Hedgehog signaling pathway is related to the occurrence and development of a variety of tumors, but the effect of this signaling pathway on melanoma cells is still unclear. Methods. This study aimed to discuss the effect of Hedgehog signaling pathway on the proliferation and apoptosis of human malignant melanoma A375 cells and explore its possible mechanism in the proliferation and apoptosis of melanoma cells. Different concentrations of Hedgehog signaling pathway inhibitor cyclopamine (5, 10, 20 and 40 μM) were used to treat human melanoma A375 cells for 24, 48, and 72 h, and set a blank control group (0 μM). Trypan blue cell counting method was used to detect cell viability. MTT method was used to detect the inhibition rate of cell proliferation. Transwell was used to detect cell invasion, and flow cytometry was used to detect cell apoptosis. Results. Through the trypan blue cell counting method and MTT experiment, it was found that the Hedgehog signaling pathway inhibitor cyclopamine has an inhibitory effect on the proliferation and viability of melanoma A375 cells ( P < 0.05 ), and the proliferation inhibitory effect is enhanced with prolonged action time in a dose- and time-dependent manner. Transwell experiment showed that compared with the blank control group, the invasion and migration ability of the treated melanoma A375 cells are significantly reduced, and the difference is statistically significant ( P < 0.05 ). Cell apoptosis experiment showed that compared with the blank control group, the apoptosis rate of A375 cells is significantly higher after treated by 40 μM cyclopamine for 24 h, and the difference is statistically significant ( P < 0.05 ). Gli1 and Bcl-2 protein are highly expressed in melanoma A375 cells, and their expressions show a downward trend ( P < 0.05 ) after being treated by cyclopamine. Conclusion. Cyclopamine inhibits cell proliferation and induces cell apoptosis by downregulating Gli1. Hedgehog signaling pathway can be used as a new target for the treatment of malignant melanoma, and multiple measures can be used to inhibit the signaling pathway to achieve a therapeutic effect.