title: A new reporter mouse cytomegalovirus reveals maintained immediate-early gene expression but poor virus replication in cycling liver sinusoidal endothelial cells.
abstract: BACKGROUND
  The MCMV major immediate early promoter/enhancer (MIEP) is a bidirectional promoter that drives the expression of the three immediate early viral genes, namely ie1, ie2 and ie3. The regulation of their expression is intensively studied, but still incompletely understood.
  
  
  METHODS
  We constructed a reporter MCMV, (MCMV-MIEPr) expressing YFP and tdTomato under the control of the MIEP as proxies of ie1 and ie2, respectively. Moreover, we generated a liver sinusoidal endothelial cell line (LSEC-uniLT) where cycling is dependent on doxycycline. We used these novel tools to study the kinetics of MIEP-driven gene expression in the context of infection and at the single cell level by flow cytometry and by live imaging of proliferating and G0-arrested cells.
  
  
  RESULTS
  MCMV replicated to higher titers in G0-arrested LSEC, and cycling cells showed less cytopathic effect or YFP and tdTomato expression at 5 days post infection. In the first 24 h post infection, however, there was no difference in MIEP activity in cycling or G0-arrested cells, although we could observe different profiles of MIEP gene expression in different cell types, like LSECs, fibroblasts or macrophages. We monitored infected LSEC-uniLT in G0 by time lapse microscopy over five days and noticed that most cells survived infection for at least 96 h, arguing that quick lysis of infected cells could not account for the spread of the virus. Interestingly, we noticed a strong correlation between the ratio of median YFP and tdTomato expression and length of survival of infected cells.
  
  
  CONCLUSIONS
  By means of our newly developed genetic tools, we showed that the expression pattern of MCMV IE1 and IE2 genes differs between macrophages, endothelial cells and fibroblasts. Substantial and cell-cycle independent differences in the ie1 and ie2 transcription could also be observed within individual cells of the same population, and marked ie2 gene expression was associated with longer survival of the infected cells.
authors.forename: Franziska
authors.initials: F
authors.lastname: Dag
authors.forename: Adrien
authors.initials: A
authors.lastname: Weingärtner
authors.forename: Milada
authors.initials: M
authors.lastname: Butueva
authors.forename: Ianina
authors.initials: I
authors.lastname: Conte
authors.forename: Julia
authors.initials: J
authors.lastname: Holzki
authors.forename: Tobias
authors.initials: T
authors.lastname: May
authors.forename: Barbara
authors.initials: B
authors.lastname: Adler
authors.forename: Dagmar
authors.initials: D
authors.lastname: Wirth
authors.forename: Luka
authors.initials: L
authors.lastname: Cicin-Sain
mesh_terms: D000818:Animals; D019677:Artificial Gene Fusion; D002460:Cell Line; D002470:Cell Survival; D042783:Endothelial Cells / Q000821:virology*; D005347:Fibroblasts / Q000821:virology; D015870:Gene Expression; D015967:Gene Expression Regulation, Viral; D017781:Genes, Immediate-Early; D017930:Genes, Reporter; D008099:Liver / Q000821:virology*; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D008264:Macrophages / Q000821:virology; D051379:Mice; D008807:Mice, Inbred BALB C; D018146:Muromegalovirus / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic; D059010:Single-Cell Analysis; D014779:Virus Replication
chemical_list: D008164:Luminescent Proteins