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Discovery of genotype-phenotype relationships remains a major challenge in clinical medicine. Here, we combined three sources of phenotypic data to uncover a new mechanism for rare and common diseases resulting from collagen secretion deficits. Using a zebrafish genetic screen, we identified the ric1 gene as being essential for skeletal biology. Using a gene-based phenome-wide association study (PheWAS) in the EHR-linked BioVU biobank, we show that reduced genetically determined expression of RIC1 is associated with musculoskeletal and dental conditions. Whole-exome sequencing identified individuals homozygous-by-descent for a rare variant in RIC1 and, through a guided clinical re-evaluation, it was discovered that they share signs with the BioVU-associated phenome. We named this new Mendelian syndrome CATIFA (cleft lip, cataract, tooth abnormality, intellectual disability, facial dysmorphism, attention-deficit hyperactivity disorder) and revealed further disease mechanisms. This gene-based, PheWAS-guided approach can accelerate the discovery of clinically relevant disease phenome and associated biological mechanisms.
There are intense interests in discovering proregenerative medicine leads that can promote cardiac differentiation and regeneration, as well as repair damaged heart tissues. We have combined zebrafish embryo-based screens with cardiomyogenesis assays to discover selective small molecules that modulate heart development and regeneration with minimal adverse effects. Two related compounds with novel structures, named as Cardiomogen 1 and 2 (CDMG1 and CDMG2), were identified for their capacity to promote myocardial hyperplasia through expansion of the cardiac progenitor cell population. We find that Cardiomogen acts as a Wnt inhibitor by targeting β-catenin and reducing Tcf/Lef-mediated transcription in cultured cells. CDMG treatment of amputated zebrafish hearts reduces nuclear β-catenin in injured heart tissue, increases cardiomyocyte (CM) proliferation, and expedites wound healing, thus accelerating cardiac muscle regeneration. Importantly, Cardiomogen can alleviate the functional deterioration of mammalian hearts after myocardial infarction. Injured hearts exposed to CDMG1 display increased newly formed CMs and reduced fibrotic scar tissue, which are in part attributable to the β-catenin reduction. Our findings indicate Cardiomogen as a Wnt inhibitor in enhancing injury-induced CM proliferation and heart regeneration, highlighting the values of embryo-based small molecule screens in discovery of effective and safe medicine leads.
© The Author(s) (2019). Published by Oxford University Press on behalf of Journal of Molecular Cell Biology, IBCB, SIBS, CAS. All rights reserved.
Aberrant activation of the Hedgehog signaling pathway has been linked to the formation of numerous cancer types, including the myogenic soft tissue sarcoma, embryonal rhabdomyosarcoma (eRMS). Here, we report , a novel mouse model in which human GLI2A, a constitutive activator of Hedgehog signaling, induced undifferentiated sarcomas that were phenotypically divergent from eRMS. Rather, sarcomas arising in mice featured some characteristics that were reminiscent of Ewing sarcoma. Even though it is widely understood that Ewing sarcoma formation is driven by gene fusions, a genetically defined mouse model is not well-established. While gene fusions were not present in sarcomas, precluding their designation as Ewing sarcoma, we did find that GLI2A induced expression of known gene targets essential to Ewing pathogenesis, most notably, . Moreover, we found that naïve mesenchymal progenitors originate tumors in mice. Altogether, our work provides a novel genetic mouse model, which directly connects oncogenic Hedgehog activity to the etiology of undifferentiated soft tissue sarcomas for the first time. IMPLICATIONS: The finding that activation of Gli2 transcription factor is sufficient to induce Ewing-like sarcomas provides a direct transformative role of the Hedgehog signaling pathway in undifferentiated soft tissue sarcoma.
©2019 American Association for Cancer Research.
While innate behaviors are conserved throughout the animal kingdom, it is unknown whether common signaling pathways regulate the development of neuronal populations mediating these behaviors in diverse organisms. Here, we demonstrate that the Wnt/ß-catenin effector Lef1 is required for the differentiation of anxiolytic hypothalamic neurons in zebrafish and mice, although the identity of Lef1-dependent genes and neurons differ between these 2 species. We further show that zebrafish and Drosophila have common Lef1-dependent gene expression in their respective neuroendocrine organs, consistent with a conserved pathway that has diverged in the mouse. Finally, orthologs of Lef1-dependent genes from both zebrafish and mouse show highly correlated hypothalamic expression in marmosets and humans, suggesting co-regulation of 2 parallel anxiolytic pathways in primates. These findings demonstrate that during evolution, a transcription factor can act through multiple mechanisms to generate a common behavioral output, and that Lef1 regulates circuit development that is fundamentally important for mediating anxiety in a wide variety of animal species.
Decreasing glucagon action lowers the blood glucose and may be useful therapeutically for diabetes. However, interrupted glucagon signaling leads to α cell proliferation. To identify postulated hepatic-derived circulating factor(s) responsible for α cell proliferation, we used transcriptomics/proteomics/metabolomics in three models of interrupted glucagon signaling and found that proliferation of mouse, zebrafish, and human α cells was mTOR and FoxP transcription factor dependent. Changes in hepatic amino acid (AA) catabolism gene expression predicted the observed increase in circulating AAs. Mimicking these AA levels stimulated α cell proliferation in a newly developed in vitro assay with L-glutamine being a critical AA. α cell expression of the AA transporter Slc38a5 was markedly increased in mice with interrupted glucagon signaling and played a role in α cell proliferation. These results indicate a hepatic α islet cell axis where glucagon regulates serum AA availability and AAs, especially L-glutamine, regulate α cell proliferation and mass via mTOR-dependent nutrient sensing.
Copyright © 2017 Elsevier Inc. All rights reserved.
Control of organellar assembly and function is critical to eukaryotic homeostasis and survival. Gle1 is a highly conserved regulator of RNA-dependent DEAD-box ATPase proteins, with critical roles in both mRNA export and translation. In addition to its well-defined interaction with nuclear pore complexes, here we find that Gle1 is enriched at the centrosome and basal body. Gle1 assembles into the toroid-shaped pericentriolar material around the mother centriole. Reduced Gle1 levels are correlated with decreased pericentrin localization at the centrosome and microtubule organization defects. Of importance, these alterations in centrosome integrity do not result from loss of mRNA export. Examination of the Kupffer's vesicle in Gle1-depleted zebrafish revealed compromised ciliary beating and developmental defects. We propose that Gle1 assembly into the pericentriolar material positions the DEAD-box protein regulator to function in localized mRNA metabolism required for proper centrosome function.
© 2017 Jao et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).
The refractivity and transparency of the ocular lens is dependent on the stability and solubility of the crystallins in the fiber cells. A number of mutations of lens crystallins have been associated with dominant cataracts in humans and mice. Of particular interest were γB- and γD-crystallin mutants linked to dominant cataracts in mouse models. Although thermodynamically destabilized and aggregation-prone, these mutants were found to have weak affinity to the resident chaperone α-crystallin in vitro To better understand the mechanism of the cataract phenotype, we transgenically expressed different γD-crystallin mutants in the zebrafish lens and observed a range of lens defects that arise primarily from the aggregation of the mutant proteins. Unlike mouse models, a strong correlation was observed between the severity and penetrance of the phenotype and the level of destabilization of the mutant. We interpret this result to reflect the presence of a proteostasis network that can "sense" protein stability. In the more destabilized mutants, the capacity of this network is overwhelmed, leading to the observed increase in phenotypic penetrance. Overexpression of αA-crystallin had no significant effects on the penetrance of lens defects, suggesting that its chaperone capacity is not limiting. Although consistent with the prevailing hypothesis that a chaperone network is required for lens transparency, our results suggest that αA-crystallin may not be efficient to inhibit aggregation of lens γ-crystallin. Furthermore, our work implicates additional inputs/factors in this underlying proteostasis network and demonstrates the utility of zebrafish as a platform to delineate mechanisms of cataract.
© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.
The zebrafish pineal complex consists of four cell types (rod and cone photoreceptors, projection neurons and parapineal neurons) that are derived from a single pineal complex anlage. After specification, parapineal neurons migrate unilaterally away from the rest of the pineal complex whereas rods, cones and projection neurons are non-migratory. The transcription factor Tbx2b is important for both the correct number and migration of parapineal neurons. We find that two additional transcription factors, Flh and Nr2e3, negatively regulate parapineal formation. Flh induces non-migratory neuron fates and limits the extent of parapineal specification, in part by activation of Nr2e3 expression. Tbx2b is positively regulated by Flh, but opposes Flh action during specification of parapineal neurons. Loss of parapineal neuron specification in Tbx2b-deficient embryos can be partially rescued by loss of Nr2e3 or Flh function; however, parapineal migration absolutely requires Tbx2b activity. We conclude that cell specification and migration in the pineal complex are regulated by a network of at least three transcription factors.
© 2016. Published by The Company of Biologists Ltd.
Some vertebrate species have evolved means of extending their visual sensitivity beyond the range of human vision. One mechanism of enhancing sensitivity to long-wavelength light is to replace the 11-cis retinal chromophore in photopigments with 11-cis 3,4-didehydroretinal. Despite over a century of research on this topic, the enzymatic basis of this perceptual switch remains unknown. Here, we show that a cytochrome P450 family member, Cyp27c1, mediates this switch by converting vitamin A1 (the precursor of 11-cis retinal) into vitamin A2 (the precursor of 11-cis 3,4-didehydroretinal). Knockout of cyp27c1 in zebrafish abrogates production of vitamin A2, eliminating the animal's ability to red-shift its photoreceptor spectral sensitivity and reducing its ability to see and respond to near-infrared light. Thus, the expression of a single enzyme mediates dynamic spectral tuning of the entire visual system by controlling the balance of vitamin A1 and A2 in the eye.
Copyright © 2015 Elsevier Ltd. All rights reserved.
There are two major stem cell populations in the intestinal crypt region that express either Bmi1 or Lgr5; however, it has been shown that other populations in the crypt can regain stemness. In this study, we demonstrate that the transcription factor NK2 homeobox 2 (Nkx2.2) is expressed in enteroendocrine cells located in the villus and crypt of the intestinal epithelium and is coexpressed with the stem cell markers Bmi1 and Lgr5 in a subset of crypt cells. To determine whether Nkx2.2-expressing enteroendocrine cells display cellular plasticity and stem cell potential, we performed genetic lineage tracing of the Nkx2.2-expressing population using Nkx2.2(Cre/+);R26RTomato mice. These studies demonstrated that Nkx2.2+ cells are able to give rise to all intestinal epithelial cell types in basal conditions. The proliferative capacity of Nkx2.2-expressing cells was also demonstrated in vitro using crypt organoid cultures. Injuring the intestine with irradiation, systemic inflammation, and colitis did not enhance the lineage potential of Nkx2.2-expressing cells. These findings demonstrate that a rare mature enteroendocrine cell subpopulation that is demarcated by Nkx2.2 expression display stem cell properties during normal intestinal epithelial homeostasis, but is not easily activated upon injury.
Copyright © 2015 the American Physiological Society.