Inflammatory bowel disease (IBD) affects 1.5-3.0 million people in the United States. IBD is genetically determined and many common risk alleles have been identified. Yet, a large proportion of genetic predisposition remains unexplained. In this study we report the identification of an ultrarare missense variant (NM_006998.3:c.230G>A;p.Arg77His) in the SCGN gene causing Mendelian early-onset ulcerative colitis. SCGN encodes a calcium sensor that is exclusively expressed in neuroendocrine lineages, including enteroendocrine cells and gut neurons. SCGN interacts with the SNARE complex, which is required for vesicle fusion with the plasma membrane. We show that the SCGN mutation identified impacted the localization of the SNARE complex partner, SNAP25, leading to impaired hormone release. Finally, we show that mouse models of Scgn deficiency recapitulate impaired hormone release and susceptibility to DSS-induced colitis. Altogether, these studies demonstrate that functional deficiency in SCGN can result in intestinal inflammation and implicates the neuroendocrine cellular compartment in IBD.
Sequencing data have been deposited in GEO under accession code GSE134202.data generated during this study is included in the manuscript.
Transcriptome-wide gene-expression analysis of colonic epithelium from enteroendocrine cell-deficient miceNCBI Gene Expression Omnibus, GSE134202.
- Luis F Sifuentes-Dominguez
- Luis F Sifuentes-Dominguez
- Linda A Baker
- Jonathan J Rios
- Da Jia
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Animal experimentation: Murine studies were approved by the UT Southwestern Institutional Animal Care and Use Committee under study number APN 102011. All zebrafish (Danio rerio) experiments were performed according to standard procedures, and were performed in accordance with the guidelines of the animal ethical committee of Sichuan University.
Human subjects: All human studies were carried out in accordance with UT Southwestern Medical Center institutional review board guidelines under an approved protocol (STU 112010-130). All subjects agreed to participation and written informed consent was obtained from all participants or legal guardians. Assent was obtained from individuals older than 10 years of age at time of enrollment.
- Andrew J MacPherson, University of Bern, Switzerland
© 2019, Sifuentes-Dominguez et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
The environmental pathogen Cryptococcus neoformans claims over 180,000 lives each year. Survival of this basidiomycete at host CO2 concentrations has only recently been considered an important virulence trait. Through screening gene knockout libraries constructed in a CO2-tolerant clinical strain, we found mutations leading to CO2 sensitivity are enriched in pathways activated by heat stress, including calcineurin, Ras1-Cdc24, cell wall integrity, and Regulator of Ace2 and Morphogenesis (RAM). Overexpression of Cbk1, the conserved terminal kinase of the RAM pathway, partially restored defects of these mutants at host CO2 or temperature levels. In ascomycetes such as Saccharomyces cerevisiae and Candida albicans, transcription factor Ace2 is an important target of Cbk1, activating genes responsible for cell separation. However, no Ace2 homolog or any downstream component of the RAM pathway has been identified in basidiomycetes. Through in vitro evolution and comparative genomics, we characterized mutations in suppressors of cbk1Δ in C. neoformans that partially rescued defects in CO2 tolerance, thermotolerance, and morphology. One suppressor is the RNA translation repressor Ssd1, which is highly conserved in ascomycetes and basidiomycetes. The other is a novel ribonuclease domain-containing protein, here named PSC1, which is present in basidiomycetes and humans but surprisingly absent in most ascomycetes. Loss of Ssd1 in cbk1Δ partially restored cryptococcal ability to survive and amplify in the inhalation and intravenous murine models of cryptococcosis. Our discoveries highlight the overlapping regulation of CO2 tolerance and thermotolerance, the essential role of the RAM pathway in cryptococcal adaptation to the host condition, and the potential importance of post-transcriptional control of virulence traits in this global pathogen.
Dysregulation of the imprinted H19/IGF2 locus can lead to Silver-Russell syndrome (SRS) in humans. However, the mechanism of how abnormal H19/IGF2 expression contributes to various SRS phenotypes remains unclear, largely due to incomplete understanding of the developmental functions of these two genes. We previously generated a mouse model with humanized H19/IGF2 imprinting control region (hIC1) on the paternal allele that exhibited H19/Igf2 dysregulation together with SRS-like growth restriction and perinatal lethality. Here, we dissect the role of H19 and Igf2 in cardiac and placental development utilizing multiple mouse models with varying levels of H19 and Igf2. We report severe cardiac defects such as ventricular septal defects and thinned myocardium, placental anomalies including thrombosis and vascular malformations, together with growth restriction in mouse embryos that correlated with the extent of H19/Igf2 dysregulation. Transcriptomic analysis using cardiac endothelial cells of these mouse models shows that H19/Igf2 dysregulation disrupts pathways related to extracellular matrix and proliferation of endothelial cells. Our work links the heart and placenta through regulation by H19 and Igf2, demonstrating that accurate dosage of both H19 and Igf2 is critical for normal embryonic development, especially related to the cardiac-placental axis.