The pim proto-oncogenes encode protein kinases, that play a role in haematopoietic cell differentiation. Overproduction of the Pim proteins in mouse lymphocytes results in increased leukemia incidence. The signal transduction pathway involved in this developmental proces is largely unknown. Two pim gene homologues from C. elegans, pim related kinase 1 and 2 (
prk-1 and
prk-2) have been cloned and sequenced. Using both GFP and lacZ fusion constructs, the expression pattern of the prk genes has been elucidated. Both genes are predominantly expressed in the pharynx, in muscle and epithelial cells. Furthermore,
prk-1 expression was found in body wall muscle and vulval muscles.
prk-2 is also expressed in cells surrounding the anus. The role of the PRK proteins in signal transduction was investigated further by the generation of several different mutant animals. Tc1 insertions were identified in both
prk-1 and
prk-2, which are homozygous viable and show no obvious phenotype. Among the progeny of the
prk-1 Tc1 insertion containing nematodes mutants have been isolated in which the Tc1 element and approximately 2 kb flanking genomic DNA was deleted. This deletion is probably a loss of function allele. However, also this mutation is homozygous viable and shows no obvious phenotype. The screening for deletion mutants of the
prk-2 gene is currently in progress. Furthermore, transgenic animals have been generated that carry multiple copies of the wild type prk genes or a dominant negative version of the prk genes, regulated by their own promoter or the heat shock promoter. Also these mutant nematodes show no obvious phenotype. Mutant animals that exhibit an obvious phenotype will be used in suppressor studies to search for upstream and downstream factors in the Prk signalling pathway. An alternative mutant screen, which will be employed if no phenotypes can be discerned will be discussed.