Genetics, Cell Biology, and Development (GCD)
Microbiology, Immunology, and Cancer Biology (MICAB)
The central nervous system (CNS) is a tightly organized structure made up of thousands of cell types. The molecular mechanisms responsible for orchestrating CNS development involve the action of inductive signals; one such signal is Sonic Hedgehog (SHH), which is both necessary and sufficient for induction and differentiation of several neural cell lineages. The cerebellum originates from two distinct progenitor populations, subventricular zone (SVZ) precursors and granule neuron precursor cells (GNPCs).
Our laboratory recently identified Rho GTPase activating protein 36 (ARHGAP36) as a novel regulator of SHH signaling in a forward genetic screen for medulloblastoma (MB) in mice. MB is a heterogenous disease made up of four distinct subgroups: SHH, wingless (WNT), group 3 and group 4. Researchers have postulated that distinct cells of origin may be associated with each subgroup, and SVZ precursors and GNPCs lead exclusively to WNT and SHH MB, respectively. ARHGAP36 overexpression was associated with group 3 and 4 MB in mice and humans, though the cell of origin of which has not been defined. ARHGAP36 expression activates SHH signaling which may be its contributing role in MB development. SHH’s roles in stem cell maintenance and function also implicates a role for ARHGAP36 in both regulating cancer stem cells within a tumor and in normal CNS development.
We plan to elucidate ARHGAP36’s role in both tumorigenesis and normal development using in vivo overexpression models. We will use a doxycycline-inducible model to specifically overexpress ARHGAP36 in the developing CNS. We hypothesize that ARHGAP36 overexpression will induce tumor formation and disrupt normal CNS development. We are also performing in vitro gain of function experiments in which we have overexpressed ARHGAP36 in an immortalized cerebellar progenitor cell line (C17). We hypothesize that ARHGAP36 overexpression will drive tumor formation in C17 cells. We also performed reverse phase protein array and RNA sequencing analysis on WT and ARHGAP36 overexpressing C17 cells to determine the consequences of increased ARHGAP36 expression in an unbiased manner.