Gene expression analysis of ErbB family signaling: Encodement of signaling specificity and identification of targets of ErB2 and ErbB4

ErbB2 and ErbB4, two members of the ErbB family of receptor tyrosine kinases (RTKs), display the greatest contrast in their functions during development and pathogenesis. We suggest that the two receptors mediate the varying functions by differentially influencing gene expression.; Transcriptional profiling was performed using cDNA and oligonucleotide microarrays. We describe the development and validation of the array methodology used in the dissertation. Our experimental results suggest that the arrays provide an efficient high throughput screening method for identification of receptor targets. However, post analysis validation including sequence verification and independent quantification of transcript changes is required.; Agonistic antibodies, ErbB2Ab and ErbB4Ab, were used to activate the two receptors in isolation from the other ErbB members. Expression analysis upon activation of ErbB2 and ErbB4 homomers results in distinct patterns of gene regulation with about a third of the genes being commonly regulated. Receptor specific targets were identified. Quantitative RT-PCR analysis of the transcript changes of a subset of identified genes demonstrated a preferential regulation of gene targets by the two receptors.; We further demonstrate that the activating ligand is able to refine signaling from a single ErbB receptor. ErbB4Ab and NRG (an ErbB4 ligand) activation of ErbB4 homomers in CEM/4 cells resulted in distinct transcriptional profiles. Ligand dependent signaling could partly explain the disparate profiles obtained between ErbB4Ab and NRG stimulated T47D cells, and between HB-EGF (an ErbB4 ligand) and NRG stimulated Sum44 cells. Our data raise the possibility that receptors activated in a homodimer by ErbB4Ab and HB-EGF have distinct profiles from those activated by NRG, which mainly promotes receptor heteromers.; This study is the first description of transcription profiles for ErbB2 and ErbB4 receptors acting singly. Many of the identified targets have known roles in ErbB target tissues including mammary gland (b-casein, CSFlR), nervous system (GABA, neurogenins) and cardiac development (GATA4, serotonin receptor). The ErbB receptors play a central role in breast cancer. The anomalous expression and functioning of several of the identified targets in breast tumors has clear implications for cancer diagnosis and therapeutics.