Semester

Fall

Date of Graduation

2012

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Department

Neurology

Committee Chair

George A Spirou

Abstract

Brain development is inextricably linked to changes in gene expression. Providing insight into the mechanisms controlling these complex events is a current challenge in neuroscience. Neurons in the medial nucleus of the trapezoid body (MNTB) receive large specialized glutamatergic nerve terminals, the calyces of Held, which grow very quickly between postnatal day 2 (P2) and P4. Through both quantitative real-time PCR (qPCR) and microarray analysis, we examined the gene expression over time for a select group of voltage-gated potassium channels controlling ion channel function and composition to finely tune their biophysical properties. Low threshold activated potassium channels subunits Kv1.1 (Kcna1) and Kv1.2 (Kcna2) both increase between P0 and P6. However, between P6 and P14, Kcna1 continues to increase while Kcna2 stays more constant. Delayed rectifier potassium channels (Kv3 family), Kv3.1 (Kcnc1) levels increase slowly between P0 and P14 while Kv3.3 (Kcnc3) levels are stable between P0 and P6 followed by a sharp increase between P6 and P14. Hcn2, a member of the hyperpolarization-activated and cyclic nucleotide-gated channel family controlling hyperpolarization-activated current (IH), also showed stable expression between P0 and P6 followed by an increase between P6 and P14. These data suggest that potassium channel composition changes dynamically during early postnatal development of the MNTB.;We next characterized the genome-wide changes in the MNTB/calyx of Held developmental system utilizing microarrays and dense temporal sampling at ages surrounding growth of the calyceal inputs between P0 and P6. We identified a list of 541 significantly changing genes and clustered them into eight groups based upon their temporal expression profiles. Candidates originating from each of the profile groups were validated by qPCR and showed excellent correlation between both techniques. Many of the changing transcripts are associated with astrocytes and oligodendrocytes in addition to the neuronal contribution. Gene ontology revealed enrichment of genes involved in axon pathfinding and cell adhesion. These results provide a genetic framework for future investigation of mechanisms associated with nerve terminal growth and maturation.

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