Mariah Denhart, Chapman Lab
ECTOPIC EXPRESSION OF T-BOX FACTORS CAUSES LIMB DEFECTS IN MICE
The T-box proteins are an evolutionarily conserved family of transcription factors, found in organisms ranging from C. elegans to humans. All members share a conserved DNA binding domain (T-domain) and thus can potentially bind to the same core DNA sequence. Outside of the T- domain, however, the proteins are quite diverse, suggesting that they function differently to regulate transcription. Interestingly, human disorders, such as Holt-Oram syndrome and ulnar-mammary syndrome, result from haploinsufficient levels of Tbx5 and Tbx3, respectively. This dosage sensitivity combined with the shared T-domain leads to the hypothesis that when co-expressed a competition at target genes can occur. For example, vertebrates may rely on T-box competition for normal limb development since as many 6 T-box factors are known to be expressed during limb formation. Using an inducible expression system, I ectopically expressed the T-box factor Brachyury (T) or Tbx6 in the developing mouse limb. Depending on the T-box factor expressed and the inducible system used, different limb phenotypes are observed. To characterize these phenotypes, I have used skeletal staining, whole mount in situ hybridization and cell death assays. Interestingly, the limb phenotypes are reminiscent of those observed in Holt-Oram patients and in mice expressing low levels of Tbx5 and are consistent with our hypothesis that when co-expressed, T-box factors can compete. To further understand the phenotypes, future experiments include transcriptional analysis (RNA-seq) and quantitation of cell death and proliferation in control versus transgenic embryos.
Friday, November 2nd
12 PM
A219B Langley Hall