Defining the role of the gamma-tubulin ring complex (gamma-TuRC) in retinal and brain vascular development

About This Grant

Project Summary: Neurodevelopmental disorders, including syndromic disorders of retinal and brain development, are a major cause of morbidity in children. A subset of these disorders results from abnormal vascular development, and microcephaly and chorioretinopathy (MCCRP) is a recently identified disease that may belong in this category. It is characterized by small head circumference, brain anomalies, developmental delay, and vision loss due to chorioretinopathy and abnormal retinal vasculature. Autosomal recessive MCCRP results from defects in TUBGCP4 or TUBGCP6, which encode components of the gamma-tubulin ring complex (γ-TuRC), a ubiquitous structure necessary for microtubule nucleation and spindle formation in cells. However, γ-TuRC has not previously been implicated in vascular development and it is unknown why defects in γ-TuRC lead to blindness and microcephaly. We demonstrated that Tubgcp4 and Tubgcp6 expression is highly upregulated in murine vascular endothelial cells (EC) from the retina and brain (relative to EC from other tissues), and that murine EC deficiency of TUBGCP4 results in embryonic lethality, indicating a critical role for TUBGCP4 in EC. Our long-term goal is to identify the role of the γ-TuRC in retinal and brain development. The objective of this application is to define the pathophysiology of TUBGCP4 and TUBGCP6-associated MCCRP. We will test the hypothesis that TUBGCP4 and TUBGCP6 serve critical, EC-specific roles in the retina and brain, and that deficiency of these proteins results in MCCRP due to a primary vascular developmental defect. Since retinal and cerebral vascular development is not complete until several weeks after birth, we will use novel conditional knockout mouse models of Tubgcp4 and Tubgcp6 and a tamoxifen-inducible EC-specific Cre recombinase to eliminate expression of these genes in EC postnatally. Ophthalmic studies will demonstrate the necessity of EC-specific TUBGCP4 and TUBGCP6 in retina and retinal vascular development, including optical coherence tomography (OCT), OCT-angiography, electroretinogram, optokinetic response, and retinal histology (Aim 1). Neurologic studies in mice and/or embryos lacking TUBGCP4 or TUBGCP6 in EC will demonstrate the necessity of these proteins in cerebral and neurovascular development, including MRI brain imaging, neurobehavioral studies, and brain immunohistochemistry (Aim 2). Elucidating the pathophysiology of MCCRP will improve our understanding of the genetic mechanisms controlling retinal and brain vascular development, and may reveal new therapeutic targets for more common blinding retinal vascular diseases. The career development objective of this proposal is to develop the mentorship and expertise needed to become a productive independent clinician-scientist and international leader working at the intersection of inherited retinal diseases (IRD) and disorders of vascular development. OHSU is a center of renowned expertise in IRDs, in vivo retinal vascular imaging, and the neurosciences; it provides state of the art resources and world-class faculty to support Dr. Everett’s scientific and career development goals for this proposal.