Developmental disruptions underlying brain abnormalities in ciliopathies

Primary cilia are essential conveyors of signals underlying major cell functions. Cerebral cortical progenitors and neurons have a primary cilium. The significance of cilia function for brain development and function is evident in the plethora of developmental brain disorders associated with human ciliopathies. Nevertheless, the role of primary cilia function in corticogenesis remains largely unknown. Here we delineate the functions of primary cilia in the construction of cerebral cortex and their relevance to ciliopathies, using an shRNA library targeting ciliopathy genes known to cause brain disorders, but whose roles in brain development are unclear. We used the library to query how ciliopathy genes affect distinct stages of mouse cortical development, in particular neural progenitor development, neuronal migration, neuronal differentiation and early neuronal connectivity. Our results define the developmental functions of ciliopathy genes and delineate disrupted developmental events that are integrally related to the emergence of brain abnormalities in ciliopathies

Arl13b in Primary Cilia Regulates the Migration and Placement of Interneurons in the Developing Cerebral Cortex

Coordinated migration and placement of interneurons and projection neurons lead to functional connectivity in the cerebral cortex; defective neuronal migration and the resultant connectivity changes underlie the cognitive defects in a spectrum of neurological disorders. Here we show that primary cilia play a guiding role in the migration and placement of postmitotic interneurons in the developing cerebral cortex, and that this process requires the ciliary protein, Arl13b. Through live imaging of interneuronal cilia we show migrating interneurons display highly dynamic primary cilia and we correlate cilia dynamics with the interneuron’s migratory state. We demonstrate that the guidance cue receptors essential for interneuronal migration localize to interneuronal primary cilia, but their concentration and dynamics are altered in the absence of Arl13b. Expression of Arl13b variants known to cause Joubert syndrome induce defective interneuronal migration, suggesting that defects in cilia-dependent interneuron migration may underlie the neurological defects in Joubert syndrome patients

Arl13b-regulated cilia activities are essential for polarized radial glial scaffold formation

The construction of cerebral cortex begins with the formation of radial glia. Once formed, polarized radial glial cells divide either symmetrically or asymmetrically to balance appropriate production of progenitor cells and neurons. Upon birth, neurons use the processes of radial glia as scaffolding for oriented migration. Radial glia thus provide an instructive structural matrix to coordinate the generation and placement of distinct groups of cortical neurons in the developing cerebral cortex. Here we show that Arl13b, a cilia-specific small GTPase mutated in Joubert syndrome patients, is critical for the initial formation of the polarized radial progenitor scaffold. Through developmental stage-specific deletion of Arl13b in mouse cortical progenitors, we found that early neuroepithelial deletion of ciliary Arl13b leads to a reversal in the apical-basal polarity of radial progenitors and aberrant neuronal placement. Arl13b modulates ciliary signaling necessary for radial glial polarity. Our findings demonstrate that Arl13b signaling in primary cilia is important for the initial formation of a polarized radial glial scaffold and suggest that disruption of this process may contribute to aberrant neurodevelopment and brain abnormalities in Joubert syndrome-related ciliopathies

Doublecortin maintains bipolar shape and nuclear translocation during migration in the adult forebrain

The ability of the mature mammalian nervous system to continually produce neuronal precursors is of considerable importance, as manipulation of this process might one day permit the replacement of cells lost as a result of injury or disease. In mammals, the anterior subventricular zone (SVZa) region is one of the primary sites of adult neurogenesis. Here we show that doublecortin (DCX), a widely used marker for newly generated neurons, when deleted in mice results in a severe morphological defect in the rostral migratory stream and delayed neuronal migration that is independent of direction or responsiveness to Slit chemorepulsion. DCX is required for nuclear translocation and maintenance of bipolar morphology during migration of these cells. Our data identifies a critical function for DCX in the movement of newly generated neurons in the adult brain

Polarity regulation during neuronal migration and differentiation

A key requirement of normal brain development is that during their proliferation, migration and differentiation precursors and daughter neurons establish and maintain a specific cell polarity, defined as having one or more axes of symmetry. Cell polarization divides the cell into different functional domains and facilitates the orientation of neurons within the overall brain framework, allowing functional connections to be established. In this dissertation I will describe work I have performed to address the question of how cell polarity is regulated during neuron migration and differentiation. I will address how the cytoskeleton and cell polarity are dynamically regulated in migrating neurons of the embryonic and adult forebrain. Specifically, I will investigate how the position of the centrosome is regulated in response to guidance cues in tangentially migrating neurons. To visualize the centrosome I have generated a transgenic mouse line that expresses a GFP- tagged centrosomal protein. In vitro studies were conducted using tangentially migrating neurons from postnatal transgenic mice to determine what molecules regulate the centrosome's position. I found that the polarity molecules GSK-3[Beta] and aPKC[Xi] regulate the centrosome's position and that repolarization in response to guidance cues depends the activity of these factors. Additionally, I analyze centrosomal position during radial migration in the embryonic cortex and report on the effect of disrupting polarity factors during migration. Next I report on the role of the microtubule-associated protein Doublecortin (DCX) in tangentially migrating neurons and show that loss of DCX results in inefficient consolidation of a single leading process during migration. Lastly, I show that during radial migration in embryogenesis, DCX cooperates with its gene-family member DCK1 to exit the multipolar stage of migration and assume a bipolar morpholog

Ophthalmologist–Patient Communication, Self-efficacy, and Glaucoma Medication Adherence

OBJECTIVE: The objective of the study was to examine the association between provider-patient communication, glaucoma medication adherence self-efficacy, outcome expectations, and glaucoma medication adherence. DESIGN: Prospective observational cohort study. PARTICIPANTS: 279 patients with glaucoma who were newly prescribed or on glaucoma medications were recruited at six ophthalmology clinics. METHODS: Patients’ visits were video-tape recorded and communication variables were coded using a detailed coding tool developed by the authors. Adherence was measured using Medication Event Monitoring Systems for 60 days after their visits. MAIN OUTCOME MEASURES: The following adherence variables were measured for the 60 day period after their visits: whether the patient took 80% or more of the prescribed doses, percent correct number of prescribed doses taken each day, and percent prescribed doses taken on time. RESULTS: Higher glaucoma medication adherence self-efficacy was positively associated with better adherence with all three measures. African American race was negatively associated with percent correct number of doses taken each day (beta= −0.16, p<0.05) and whether the patient took 80% or more of the prescribed doses (odds ratio=0.37, 95% confidence interval 0.16, 0.86). Physician education about how to administer drops was positively associated with percent correct number of doses taken each day (beta= 0.18, p<0.01) and percent prescribed doses taken on time (beta=0.15, p<0.05). CONCLUSIONS: These findings indicate that provider education about how to administer glaucoma drops and patient glaucoma medication adherence self-efficacy are positively associated with adherence