| Summary: | The bli-4 gene of Caenorhabditis elegans encodes at least four gene
products by the mechanism of alternative splicing. Termed blisterases A-D,
these isoforms contain unique carboxyl termini and exhibit distinct structural
homology to different members of the kexin family of proprotein
convertases. Two different kinds of phenotypes have been identified in our
collection of bli-4 mutants: blistering at the adult stage of the allele e937, and
embryonic (or early larval) lethality of thirteen alleles, suggesting bli-4 plays a
functional role not only in the assembly or maintenance of the adult cuticle
but also in the early development of the animal. The goal of this thesis is to
investigate the functions of the individual blisterases using isoform-specific
minigenes in a bli-4 mutant background. Three minigenes were constructed.
Together with pCeh226 containing the carboxyl terminus for blisterase A ,
these constructs provide minigenes specific for three of the isoforms, pCeh299
for blisterase B, pCeh308 and pCeh309 for blisterase C. The blistered mutant
lacks the 3' exon of blisterase A. As expected, a high copy number of the
minigene providing the blisterase A isoform rescued this phenotype. In
addition, the blisterase A minigene also rescued the lethal mutants,
suggesting either that blisterase A is required early in development or
inappropriately provides the function of the other isoforms. At high copy
number, the blisterase B minigene also rescued both the blistering and the lethal phenotypes whereas a modified blisterase C minigene (pCeh309) only
rescued the blistering phenotype. At low copy number, three out of five
transgenic lines containing the blisterase B minigene and one putative
integrated line containing blisterase C (pCeh308) also rescued blistering.
None of the arrays carrying a low copy number of minigenes rescued the
lethal mutants tested. The results support the hypothesis that high copy
number lines can inappropriately provide the function of other isoforms.
This is compatible with the suggestion that there is functional redundancy
between the isoforms, with blisterases A and B probably playing a more
important role than blisterase C as indicated by the present results. Biological
specificity may result from the developmental, or tissue-specific distribution
of the processing enzyme with its substrate. === Medicine, Faculty of === Medical Genetics, Department of === Graduate
|
|---|
