ABSTRACT
We propose a high impact collaborative project to overcome barriers to understanding the roles and regulation
of Forkhead box subfamily O transcription factors FOXO -1, -3, and -4 (FOXO) in stem cell contexts. Stem cells
repopulate the lining of the intestinal tract, muscle, and blood lineages, yet also drive devastating diseases such
as cancer. Evolutionarily conserved, partially redundant FOXO transcription factors are needed for stem cell
maintenance in a litany of contexts such as embryonic, cancer, mesenchymal, hematopoietic, and neural cell
lineages, as well as direct specification of subsequent lineages in a context-dependent manner. Canonically,
high PI3K output leads to cytoplasmic/inactive FOXO factors. Stem cells, however, are fundamentally rewired to
have both high PI3K Pathway activity and nuclear/active FOXO factors. Prior work shows that FOXO factors
directly bind to and activate stem genes in both embryonic stem cells and the poor prognosis cancer glioblastoma
multiforme (GBM) to drive stem cell fate. However, the precise mechanisms utilized by FOXO transcription
factors in driving stemness, hindering differentiation, and determining cell fate are incompletely understood. Our
novel, preliminary insights indicate that nuclear-localized FOXOs engage both the NOTCH and JAK/STAT
signaling pathways. Our preliminary evidence demonstrates a strong loss in the gene expression of NOTCH
Pathway components NOTCH1 and NOTCH3, as well as their targets including HES1, in FOXO4 loss-of-function
contexts. Our preliminary data indicates that FOXO factors share the ability to promote NOTCH output.
Motivated by our preliminary findings and published work (by others), we propose to examine whether FOXO -
1, -3, and -4 redundantly drive NOTCH1 and NOTCH3 gene expression in GBM and myoblasts. Our preliminary
work with FOXO transcription factor disruption mutants shows that FOXO4 acts uniquely to hinder JAK/STAT3
activation and expression of targets IGF1, PDGF and TH. Of note, FOXO3 disruption led to a loss in STAT3
activation, underscoring unique contributions of FOXO factors to the JAK/STAT Pathway. We propose to dissect
the ability of FOXO factors to differentially regulate the JAK/STAT Pathway in GBM and myoblast settings. Our
long-term goal is to delineate FOXO-driven fundamental biological processes that aid in stem cell maintenance
and cell fate by promoting the NOTCH Pathway and differentially regulating the JAK/STAT Pathway. The
proposed work will integrally involve student researchers (our group has successfully sent eleven students to
doctoral studies) and will promote the research environment at UTRGV, the second-largest Hispanic serving
institution in the United States.
