All ETDs from UAB

Advisory Committee Chair

Bradley K Yoder

Advisory Committee Members

Alecia Gross

Michael Miller

Chenbei Chang

Rosa Serra

Document Type

Dissertation

Date of Award

2016

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Cilia are hair-like microtubule based protrusions from the cell membrane. The Transition Zone (TZ) is a vital sub-domain of cilia and is located at the base of the cilium above the basal body at the entry point into the cilium. While multiple proteins associated with Nephronophthisis (NPHP), Bardet-Biedl Syndrome (BBS) and Meckel Gruber Syndrome (MKS) have been found to specifically localize to this region, little is known about their function. However, because non-ciliary proteins ectopically localize to the cilium in TZ mutants, it is hypothesized that TZ proteins control the trafficking of signaling proteins into and out of the cilium. NPHP and MKS proteins, named after the diseases they were first found to associate with, form two separate but genetically interacting protein complexes termed the NPHP complex and the MKS complex. In C. elegans this genetic interaction can easily be observed by dye-filling the ciliated sensory neurons with lipophilic dye. Dye-filling defects only occur when a protein from each complex is lost together; for example nphp-4;mks-1 mutants are dye-filling defective (DYF), but mks-1;mks-2 double mutants are not DYF. Capitalizing on this synthetic effect, we performed an enhancer mutagenesis screen for genetic interactors with the NPHP complex. To accomplish this we mutagenized nphp-4(tm925) mutant C. elegans and screened for DYF C. elegans whose phenotype was dependent on the original nphp-4 mutation after outcrossing. Thus far we have identified and characterized 7 genetic interactors with nphp-4. Three of the novel alleles were mks-1(yhw146), mks-2(yhw128), and mks-5(yhw91) have enabled us to rearrange the MKS complex hierarchy and verify our screen. The remaining 4 alleles were in non-TZ genes (osm-3(yhw66), bbs-5(yhw62), cca-1(yhw26), and aldo-1(yhw166)). Our data indicate that nphp-4 genetically interacts with osm-3 and bbs-5 to regulate intraflagellar transport (IFT) and ciliary protein composition. Finally our studies with aldo-1(yhw166) and bbs-5(yhw62) have show that ALDO-1 and BBS-5 are involved in regulating endocytosis of proteins from the cilium. Furthermore, through this work we have been able to further our understanding of the TZ and its involvement in ciliary protein export.

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