All ETDs from UAB

Advisory Committee Chair

Rosa Serra

Advisory Committee Members

Andra Frost

Michael Miller

Gene Siegal

Bradley Yoder

Document Type

Dissertation

Date of Award

2014

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Primary cilia (PC) extend from the cell body into the microenvironment detecting chemical and mechanical signals, and are required for proper development. To evaluate loss of primary cilia in mammary gland development, we developed mouse models with deletion of PC in mammary epithelial compartments. No discernable alterations to mammary development were observed in MMTV-Cre- or K14-Cre; Ift88Del lines. PC were expressed at high levels on cells in mammosphere culture; however, PC were not required for mammosphere renewal. The inability to find a significant mammary developmental phenotype in our mouse models suggested primary cilia don't have a significant function in differentiated cells types of the mammary gland. Conversely, it has been shown that PC are required for proper skeletal development. Mice with loss of PC in growth plate chondrocytes show disorganization of the growth plate and a reduction in overall bone length. Unloading has also been shown to alter growth plate organization. If PC are involved in sensing mechanical load, we expect PC depleted and unloaded growth plates to have comparable phenotypes. In order to unload the hindlimb, we used sciatic neurectomy and Botox injections on one limb at P8 and euthanized the mice at different time points from 2 days to 8weeks. Unloaded tibia length was significantly decreased relative to paired controls after 8weeks. Similar to PC depleted mice, unloaded tibia showed disorganized growth plates and disrupted actin cytoskeleton. Since PC orientation is more conserved in weight bearing cartilage versus non-weight bearing, we also hypothesized that load may be required for cilia orientation. PC in controls at 2 days were found facing either the resting or the hypertrophic zone. PC in controls at 2 weeks were mostly found facing the hypertrophic zone. PC orientation were similar to controls 2 days after unloading; however, after 2 weeks of unloading, PC were oriented facing either the resting zone or the hypertrophic zone. In conclusion, similar to depletion of PC, hindlimb unloading alters growth plate organization and disrupts actin cytoskeleton arrangement. Furthermore, cilia orientation becomes more defined as the growth plate matures and this orientation is dependent on loading.

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