Fishes of the genus Danio exhibit diverse pigment patterns that serve as useful models for understanding the genes and cell behaviors underlying the evolution of adult form. Among these species, zebrafish D. rerio exhibit several dark stripes of melanophores with sparse iridophores that alternate with light interstripes of dense iridophores and xanthophores. By contrast, the closely related species D. nigrofasciatus has an attenuated pattern with fewer melanophores, stripes and interstripes. Here we demonstrate species differences in iridophore development that presage the fully formed patterns. Using genetic and transgenic approaches we identify the secreted peptide Endothelin-3 (Edn3)—a known melanogenic factor of tetrapods—as contributing to reduced iridophore proliferation and fewer stripes and interstripes in D. nigrofasciatus. We further show the locus encoding this factor is expressed at lower levels in D. nigrofasciatus owing to cis-regulatory differences between species. Finally, we show that functions of two paralogous loci encoding Edn3 have been partitioned between skin and non-skin iridophores. Our findings reveal genetic and cellular mechanisms contributing to pattern differences between these species and suggest a model for evolutionary changes in Edn3 requirements for pigment patterning and its diversification across vertebrates.

Our image analysis approach enables insights into gut dynamics in a wide variety of developmental and physiological contexts and can also be extended to analyze other types of cell movements.

ers by interactions of FoxO3 with the chromatin-remodeling factor Brg1 and the TF Olig2, which are involved in control of OPC differentiation (14-16). Hence, central myelination failure is regulated by a noncanonical TLR4/AKT/FoxO3 signaling pathway utilized by bHAf to induce a tolerance-like state that selectively constrains OPC maturation and myelination. ResultsNeonatal hypoxic-ischemic WMI promotes MDa HA depolymerization. To investigate the status of MDa HA in chronic neonatal WMI, we employed our preterm-equivalent rat hypoxia-ischemia (H-I) model, which generates myelination failure and replicates key features of human WMI ( Figure 1A) (17). MDa HA turnover in the ECM after H-I was visualized with a biotinylated HA-binding protein (HABP) and costained with glial fibrillary acidic protein (GFAP) as a marker of WMI. Unlike in age-matched uninpro-myelination signal (13). This tolerance-like action of bHAf was mediated through TLR4 but not via CD44 or TLR2. As in TLR4-mediated IT, bHAf 's influence on myelination was reversible when MDa HA depolymerization was attenuated or bHAf was removed. AKT desensitization was similarly reversible in vivo in neonatal WMI. Moreover, bHAf actions were mediated via a noncanonical TRIF-dependent pathway, also involved in IT, rather than the canonical MyD88 arm of TLR4 signaling. AKT desensitization resulted in maturation-dependent activation of the FoxO3 transcription factor (TF), which selectively constrained preOL maturation in a bHAf-dependent fashion. A role for activated FoxO3 in human myelination failure was supported by selective localization of nuclear FoxO3 to OPCs in human preterm WMI and multiple sclerosis (MS) plaques. bHAf-mediated OPC maturation arrest appears to be regulated at the FoxO3 and myelin basic protein (MBP) promot- (Contralateral). Only the lesion group had a significant reduction in HA recovery. (E) Incubation of MDa HA with the lesion lysate generated HAf below ~650 kDa. Lesion-lysate activity was sensitive to heat inactivation but insensitive to deferoxamine (50 μM). B and C: control n = 2; H-I n = 4 animals for each age group (P4 and P14). D: n = 6 (H-I), n = 5 (control), and n = 4 (hypoxia) animals (P7). E: n = 4 separate experiments on 4 different animals at P4 after H-I at P3; one representative experiment is shown. *P < 0.05 by ANOVA. Mean ± SD. Scale bars: 300 μm (B and C). The Journal of Clinical Investigation R E S E A R C H A R T I C L E2 0 2 7 jci.orgVolume 128 Number 5 May 2018 with MBP-labeled oligodendrocytes (Supplemental Figure 2A). To confirm de novo progressive myelin generation, we undertook ultrastructural studies that identified axons wrapped with multilamellar myelin sheaths ( Figure 2B). In contrast to vehicle-treated slices, which displayed robust myelination of the corpus callosum, slices incubated with MDa HA until 21 days in vitro (DIV21) displayed a pronounced reduction in myelinated axons ( Figure 2C). Myelination failure was not related to decreased OPC survival, since MDa HA treatment did not enhance OPC degeneratio...

Nearly half of cancer patients suffer from cachexia, a metabolic syndrome characterized by progressive atrophy of fat and lean body mass. This state of excess catabolism decreases quality of life, ability to tolerate treatment and eventual survival, yet no effective therapies exist. Although the central nervous system (CNS) orchestrates several manifestations of cachexia, the precise mechanisms of neural dysfunction during cachexia are still being unveiled. Herein, we summarize the cellular and molecular mechanisms of CNS dysfunction during cancer cachexia with a focus on inflammatory, autonomic and neuroendocrine processes and end with a discussion of recently identified CNS mediators of cachexia, including GDF15, LCN2 and INSL3.

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