Matthew Faron and Elizabeth Leslie will present their research on 26th July 2012
Matthew Faron’s research abstract
Francisella tularensis regulators migR, trmE, and cphA control FPI gene expression and intracellular growth by modulation of the stress alarmone ppGpp.
The F. tularensis pathogenicity island encodes several proteins that are required for virulence. These genes are regulated by several proteins including: fevR, migR, trmE, and cphA. However, it is unknown how migR, trmE or cphA regulate the FPI and the FevR regulon. Bioinformatical characterization of migR, trmE, and cphA suggests a similar role for these three genes in Francisella physiology. Previous data suggest that the FevR (PigR) regulon is important for the bacteria to survive nutritionally stressful environments. In support of this idea it has been shown that the stress alarmone ppGpp is important to stabilize the interaction of MglA/SspA with FevR (PigR) and allow optimal gene expression. With these data we hypothesize that migR, trmE, and cphA modulate FevR (PigR) regulon by signaling a bacterial nutritional stress,that activates ppGpp production. To test this hypothesis thin layer chromatography was performed to measure the amount of ppGpp produced by the various mutants. To further identify the role of these genes in virulence b-gal assays measuring FPI expression and cell infections were performed with a migR, trmE, or cphA mutant. These tests were utilized to measure the ability of mutants to regulate igl expression under different stresses including varying pH and amino acid starvation, and to measure the ability of these mutants to grow in epithelial and macrophage cell lines measured by cell counts and confocal imaging. TLC demonstrated that there is a decrease in ppGpp levels in all three strains: LVSΔmigR, LVSΔtrmE and LVSΔcphA compared to LVS. Interestingly, there was a difference in ability to grow in different cell types depending upon which mutation was present in Francisella. In Hep-2 cells cphA was the only mutant to have a defect in growth whereas, in A549s both the cphA and migR mutants had a defect in replication. Our data suggest that Francisella FPI gene expression and intracellular growth is a response to stress. The observed differences in intracellular growth suggest that each cell type has a different limitation that impacts the ability of Francisella to grow. In support of the role of bacterial stress on the expression of FPI, the igl reporter gene transcription was increased in the presence of both amino acid stress and basic pH. However, when reporter strains were grown in pH 5.5, FPI gene expression was decreased. Our data indicate that the migR, trmE, and cphA regulate the FevR regulon through activation of ppGpp and sense different nutritional stresses in tissue culture cells. Furthermore, in the presence of various stresses, the FevR regulon increases in transcription. Better understanding of how Francisella regulates its virulence genes may lead to the ability to make mutants that elicit a favorable immune response for vaccine development.
Eliazabeth Leslie’s research abstract
Elucidating the genetic spectrum of orofacial clefts
Orofacial clefts are a diverse group of disorders caused by failure of normal craniofacial development. Orofacial clefts may either be isolated (nonsyndromic) or occur as syndromes with additional structural or cognitive abnormalities. Although there are over 500 syndromes in which clefting is a primary feature, 70% of all CL/P cases and 50% of a CPO cases are categorized as nonsyndromic. As a result of advances in genomics and technology, significant progress has been made in understanding orofacial clefting through genome wide association studies (GWAS) for nonsyndromic clefting and exome sequencing for syndromic, Mendelian forms. Although we typically think of Mendelian and complex disorders as distinct entities, they actually exist on the same genetic spectrum. At seminar I will share recent work identifying genes contributing to the two ends of this spectrum of orofacial clefts.