Related Experiment Videos
Functional analysis of ARHGAP6, a novel GTPase-activating protein for RhoA
S K Prakash1, R Paylor, S Jenna
1Departments of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.
Abstract:
Microphthalmia with linear skin defects (MLS) is an X-linked dominant, male-lethal syndrome characterized by microphthalmia, aplastic skin and agenesis of the corpus callosum, and is caused by the deletion of a 500 kb critical region in Xp22.3. Our laboratory isolated a novel rho GTPase-activating protein (rhoGAP) gene named ARHGAP6 from the MLS region. ARHGAP6 contains 14 exons encoding a 974 amino acid protein with three putative SH3-binding domains. Because exons 2-14 are deleted in all MLS patients, we hypothesized that ARHGAP6 may be responsible for some of the phenotypic features of MLS. We pursued two approaches to study the function of ARHGAP6 and its role in the pathogenesis of MLS: gene targeting of the rhoGAP domain in mouse embryonic stem cells and in vitro expression studies. Surprisingly, loss of the rhoGAP function of Arhgap6 does not cause any detectable phenotypic or behavioral abnormalities in the mutant mice. Transfected mammalian cells expressing ARHGAP6 lose their actin stress fibers, retract from the growth surface and extend thin, branching processes resembling filopodia. The ARHGAP6 protein co-localizes with actin filaments through an N-terminal domain and recruits F-actin into the growing processes. Mutation of a conserved arginine residue in the rhoGAP domain prevents the loss of stress fibers but has little effect on process outgrowth. These results suggest that ARHGAP6 has two independent functions: one as a GAP with specificity for RhoA and the other as a cytoskeletal protein that promotes actin remodeling.
Insights
The ARHGAP6 gene, implicated in Microphthalmia with linear skin defects (MLS), has dual functions. It acts as a RhoA-specific GTPase-activating protein (GAP) and promotes actin remodeling, influencing cell shape and cytoskeletal dynamics.
Area of Science:
- Genetics
- Cell Biology
- Developmental Biology
Background:
- Microphthalmia with linear skin defects (MLS) is an X-linked dominant, male-lethal syndrome.
- MLS is associated with deletions in a critical region at Xp22.3.
- A novel rho GTPase-activating protein (rhoGAP) gene, ARHGAP6, was identified within the MLS critical region.
Purpose of the Study:
- To investigate the function of the ARHGAP6 gene.
- To determine the role of ARHGAP6 in the pathogenesis of MLS.
- To elucidate the molecular mechanisms underlying ARHGAP6 function.
Main Methods:
- Gene targeting of the rhoGAP domain in mouse embryonic stem cells.
- In vitro expression studies of ARHGAP6 in transfected mammalian cells.
- Analysis of ARHGAP6 protein localization and interaction with actin filaments.
Main Results:
- Loss of rhoGAP function in Arhgap6 mutant mice did not result in observable abnormalities.
- ARHGAP6 expression in mammalian cells caused loss of actin stress fibers and extension of filopodia-like processes.
- ARHGAP6 co-localizes with actin filaments and recruits F-actin, suggesting a role in actin remodeling.
- Mutation of a key arginine residue in the rhoGAP domain affected stress fiber loss but not process outgrowth.
Conclusions:
- ARHGAP6 possesses two distinct functions: RhoA-specific GAP activity and promotion of actin remodeling.
- These functions suggest ARHGAP6 plays a significant role in cytoskeletal organization and cell morphology.
- The dual function of ARHGAP6 may contribute to the complex phenotype observed in MLS, although its loss alone does not fully recapitulate the syndrome.