Date of Completion
Arthur Günzl, Aoife Heaslip
Genetics and Genomics | Laboratory and Basic Science Research | Medicine and Health Sciences | Molecular Genetics | Parasitic Diseases
Human African trypanosomiasis (HAT) is a lethal disease caused by protozoan hemoflagellates of the genus Trypanosoma. Humans are vulnerable to two subspecies, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. At the crux of HAT lethality lie two uncommon genetic expression phenomena: monoallelic expression and antigenic variation. Combined, these mechanisms effectively shield trypanosomes from host immune systems, prolonging infections. Variant Surface Glycoproteins (VSGs) are the key outer membrane proteins involved in antigenic variation. By continuously changing the composition of cell surface antigens, trypanosomes can survive bouts of immunological detection and eventually traverse the blood-brain barrier. There are over two thousand VSG variants within the trypanosome genome, but only one is expressed at a time. Transcription of the active VSG is initiated by the Class I Transcription Factor A (CITFA) complex. This basal promoter-binding complex is composed of eight subunits: CITFA1-7 and dynein light chain LC8. Preliminary data suggested that CITFA7 dimerizes via LC8 and is important for expression of only a single VSG at a time. Results of a co-immunoprecipitation assay provide evidence against the possibility that CITFA7 dimerizes in vivo, while semi-quantitative and quantitative reverse-transcription PCR data support the hypothesis that CITFA7 contributes to monoallelic expression. Visualization of silent VSG derepression with indirect immunofluorescence was attempted to see whether disruption of monoallelic expression by the expression of a non-lethal mutation in CITFA7 alters the normally punctuated location of the CITFA complex within the nucleus. Results from this effort lay the groundwork for future quantitative analysis with direct fluorescence.
Platt, Sarah, "Disrupting Monoallelic Expression of Variant Surface Glycoprotein in Trypanosoma brucei by a Non-lethal Mutation in Class I Transcription Factor A" (2022). Honors Scholar Theses. 878.