Characterization of Chitin Synthases and Chitin Deacetylases that Function During the Development of the Nematode Caenorhabditis elegans.
Abstract: Chitin (beta-1,4-linked-N-acetylglucosamine) is a major structural
macromolecule in nematodes. Its presence in the eggshell and the lining of the pharynx
confers protective benefits and also facilitates important steps of development. Chitin
metabolism is considered to be highly conserved within roundworms - but not in the many
plants and vertebrates that are parasitized by some of ... read morethem - so research on chitin
metabolism will provide knowledge on basic aspects of invertebrate development and may also
provide a foundation from which to develop new drugs or vaccines targeting parasitic
nematodes. This dissertation encompasses various projects aiming to deepen our
understanding of the chitin synthases and chitin deacetylases that function during nematode
development. This body of work is the first showing that polysaccharide deacetylases (which
can convert chitin to chitosan) are encoded in a diverse array of nematode genomes. Two
copies of these genes are found in C. elegans where they are somatically expressed and
affect development since their loss results in a retardation of growth. Our knowledge of
transcript numbers and sequences, as well as on the dynamics of their expression, is
incomplete. Proteins with bona fide chitin deacetylase activity are produced in C. elegans,
and while low levels of carbohydrate limit our ability to demonstrate the presence of
chitosan using standard biochemical techniques, we show that chitosan is localized to the
C. elegans pharynx because it stains with the dye Eosin Y. Chitin synthases convert
UDP-N-acetylglucosamine into the high molecular weight homopolymer chitin and previously
published work has shown that the two genes act non-redundantly to deposit chitin in the
nematode eggshell and pharynx. The work in this dissertation further characterizes the
germline expression of the chs-1 gene and investigates novel roles and expression patterns
for both chs-1 and chs-2. The enzymatic properties of the germline and somatic chitin
synthase proteins are also studied and presented along with attempts to confirm the
presence of novel chitinous structures. This dissertation closes with a perspective on
future directions of study for nematode chitin synthases and chitin deacetylases and
outlines the significance of these enzymes in the context of biochemistry, developmental
biology and parasitology.
Thesis (Ph.D.)--Tufts University, 2012.
Submitted to the Dept. of Biology.
Advisor: Juliet Fuhrman.
Committee: Susan Ernst, Mitch McVey, Harry Bernheim, and John Samuelson.
Keywords: Biology, Developmental biology, and Biochemistry.read less