Larval Gene Expression and Genetic Variation in the Canine Hookworm, Ancylostoma caninum

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Title: Larval Gene Expression and Genetic Variation in the Canine Hookworm, Ancylostoma caninum
Author: Moser, Jennifer Marie
Advisors: Greg Gibson, Committee Chair
Prema Arasu, Committee Member
Ignazio Carbone, Committee Member
Laura Mathies, Committee Member
Abstract: The hookworm, Ancylostoma caninum is a canine parasite, and is responsible for anemia and death in infected puppies. Gene expression profiling was used to investigate transcript differences between two different forms of the third larval stage (L3s): infective free-living larvae and in vitro serum-stimulated larvae that mimic the initial stages of parasitism of a host. I developed an A. caninum cDNA microarray and used it to identify a set of 113 genes that are differentially regulated between infective and parasitic larval stages. Of the genes repressed upon serum stimulation, seven encode members of the 'Ancylostoma Secreted Protein' ASP family, while another transcript encoding a 24 kD excretory protein with similarity to ASP was up-regulated in serum-stimulated L3s. Thus, different members of a protein family that has important implications for the hookworm's parasitic lifestyle are regulated in a complementary manner in response to serum stimulation. Comparison of two strains of A. caninum from North Carolina and Maryland only identified a single gene, one of the members of the ASP family that was differentially repressed upon serum stimulation. Population genetic variation has previously been described contrasting samples from clone libraries of Baltimore and Shanghai strains of A. caninum, but variation within and among wild isolates has not been characterized. I quantified the genetic variation and population structure of several different geographical isolates of A. caninum at two loci. The cytochrome oxidase subunit 1 (cox-1) is a mitochondrial marker gene revealing moderate diversity within a Wake County isolate that is comparable to the level of variation observed in other parasitic nematodes. The protein coding gene asp-1, chosen for its possible use as a vaccine target, shows similar levels of genetic variation within Wake County as cox-1, and there is no evidence for selection acting on this locus. The genetic variation within a Maryland laboratory isolate is more limited, likely resulting from a founder event and subsequent inbreeding. I also provide evidence for gene flow both among Southeastern U.S. isolates and among global isolates, suggesting that the mobility of A. caninum's host animal is an important contributing factor to its parasite's population structure.
Date: 2006-03-02
Degree: PhD
Discipline: Functional Genomics

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