We are interested in identifying, and,as well as determining the molecular function of, the body size determining X-lin- ked gene
lon-2 of C.elegans. The loss-of-function alleles, such as the reference allele
e678 (Brenner 1974) give rise to an elongated body size of one and half of the wild type in the homozygous state. Neither any dosage compensation nor maternal effect could be demonstrated. Our aims were the mo- lecular cloning, physical mapping and sequencing of
lon-2 gene as well as to determine the function in molecular term. Apart from the exciting problem of body size
lon-2 has drawn our attention since it is probably coding for an element of a signal transduction pathway, which is of evolutionarily conserved. The argument for this is that
daf-4 gene, coding for a serine/threonine kinase receptor protein, is negative- ly regulated by
lon-2 (Savage, WBG 13. 1994). This receptor is capable of binding the human BMP-2 that is TGF-beta like ligand (Estevez et al. Nature, 1993. 365). As the first step we determined the likely position of
lon-2 on the physical map of C.elegans, that is a 100 kbp long re- gion according to the data of ACEDB, and we selected 24 over lapping cosmid clones that cover the region in question. We used the Tc-1 transposon induced allele of
lon-2 (
lon-2 (
n309); RC 309 strain, R.Cassada 1994). Using the transpo- son as a probe for a reverse PCR method, adapted for C.ele- gans in our laboratory, we identified the cosmid clones carrying a C.elegans genomic fragment capable for rescuing wild phenotype when injected into the ovaria of
lon-2 ho- mozygote recessive mutants. We then used this fragment as a probe to select two overlapping cosmid clones carrying the total sequence of
lon-2 gene. The genomic DNA fragment isolated from these cosmid clones was injected into
lon-2 mutant hermaphrodites and transgenic animals with Non-Lon phenotype were identified amongst the F1 progeny (positive mutant rescue). Using Southern hybridi- sation, we isolated the subclone containing the
lon-2 gene. The sequence of the
lon-2 gene was determined using the data of the "C.elegans sequencing project". We plan to forcast the possible function by searching for homologies between the predicted protein sequence and the established protein sequences. Using the known sequence, we isolated the promoter region of this gene and having inserted it in a pPD like expression systems, we are now working on expression pattern of
lon-2.