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The Focal Adhesion-Localized CdGAP Regulates Matrix Rigidity Sensing and Durotaxis
Motile cells are capable of sensing the stiffness of the surrounding extracellular matrix through integrin-mediated focal adhesions and migrate towards regions of higher rigidity in a process known as durotaxis. Durotaxis plays an important role in normal development and disease progression, including tumor invasion and metastasis. However, the signaling mechanisms underlying focal adhesion-mediated rigidity sensing and durotaxis are poorly understood. Utilizing matrix-coated polydimethylsiloxane gels to manipulate substrate compliance, we show that cdGAP, an adhesion-localized Rac1 and Cdc42 specific GTPase activating protein, is necessary for U2OS osteosarcoma cells to coordinate cell shape changes and migration as a function of extracellular matrix stiffness. CdGAP regulated rigidity-dependent motility by controlling membrane protrusion and adhesion dynamics, as well as by modulating Rac1 activity. CdGAP was also found to be necessary for U2OS cell durotaxis. Taken together, these data identify cdGAP as an important component of an integrin-mediated signaling pathway that senses and responds to mechanical cues in the extracellular matrix in order to coordinate directed cell motility.
Journal Article
Auditory Processing of Spectral Cues for Sound Localization in the Inferior Colliculus
The head-related transfer function (HRTF) of the cat adds directionally dependent energy minima to the amplitude spectrum of complex sounds. These spectral notches are a principal cue for the localization of sound source elevation. Physiological evidence suggests that the dorsal cochlear nucleus (DCN) plays a critical role in the brainstem processing of this directional feature. Type O units in the central nucleus of the inferior colliculus (ICC) are a primary target of ascending DCN projections and, therefore, may represent midbrain specializations for the auditory processing of spectral cues for sound localization. Behavioral studies confirm a loss of sound orientation accuracy when DCN projections to the inferior colliculus are surgically lesioned. This study used simple analogs of HRTF notches to characterize single-unit response patterns in the ICC of decerebrate cats that may contribute to the directional sensitivity of the brain's spectral processing pathways. Manipulations of notch frequency and bandwidth demonstrated frequency-specific excitatory responses that have the capacity to encode HRTF-based cues for sound source location. These response patterns were limited to type O units in the ICC and have not been observed for the projection neurons of the DCN. The unique spectral integration properties of type O units suggest that DCN influences are transformed into a more selective representation of sound source location by a local convergence of wideband excitatory and frequency-tuned inhibitory inputs.
Journal Article
Yemeni Nobel Peace Prize Winner Tawakkol Karman visits Washington
The US Institute of Peace (USIP) in Washington DC hosted 2011 Nobel Peace Prize Winner and Yemeni human rights activist Tawakkol Karman on September 8. After a brief introduction by Colette Rausch, USIP's acting vice president of governance, law, and society, and Mohamed Elsanousi, the U.S. director of the Network for Religious and Traditional Peacemakers, Karman gave a 30-minute overview of the situation in Yemen. Karman began with a recap of the 2011 uprising which led to the overthrow of long-time dictator Ali Abdullah Saleh. She described the revolution as entirely peaceful, even though high-ranking members in her own Al-Islah party declared war on the former president, which led to violent conflict throughout the country. The immunity issue aside, Karman declared the transition a great success, saying that the GCC Initiative laid the groundwork for the National Dialogue Conference.
Journal Article
Debating the war in Yemen
The National Council on US-Arab Relations hosted a high-profile event on April 2 called Yemen in Chaos at the Rayburn House Office Building on Capitol Hill. Discussing the recent developments in Yemen, mainly the Saudi-led anti-Houthi military campaign, were panelists Jeremy M Sharp of the Congressional Research Service, David Des Roches of the Near East South Asia Center for Strategic Studies, Yemeni journalist Abbas Almosawa, and Sama'a Al-Hamdani, a Yemeni analyst and writer. Saudi Arabia's new foreign minister, Adel A Al-Jubeir, who at the time was serving as the Kingdom's ambassador to the US, was the guest of honor, and undoubtedly the reason for much of the media's interest. In the end, the event was very revealing and indicative of the tension and passion that the war in Yemen provokes. It also reflects a growing disconnect between US policymakers and Yemenis struggling to survive as a result of the actions these power brokers make.
Journal Article
Author Farha Ghannam discusses masculinity in Urban Egypt
Farha Ghannam, author of Live and Die Like a Man: Gender Dynamics in Urban Egypt (available from AET's Middle East Books and More), discussed her book and her future research plans in a Feb. 27 talk at Georgetown University's Center for Contemporary Arab Studies titled \"Doing and Becoming: Masculine Trajectories in Urban Egypt.\"
Journal Article