The Dictyostelium developmental cDNA project: generation and analysis of expressed sequence tags from the first-finger stage of development.

In an effort to identify and characterize genes expressed during multicellular development ill Dictyostelium, we have undertaken a cDNA sequencing project. Using size-fractionated subsets of cDNA from the first finger stage, two sets of gridded libraries were constructed for cDNA sequencing. One, library S, consisting of 9984 clones, carries relatively short inserts, and the other, library L, which consists of 8448 clones, has longer inserts. We sequenced all the selected clones in library S from their 3'-ends, and this generated 3093 non-redundant, expressed sequence tags (ESTs). Among them, 246 ESTs hit known Dictyostelium genes and 910 showed significant similarity to genes of Dictyostelium and other organisms. For library L, 1132 clones were randomly sequenced and 471 non-redundant ESTs were obtained. In combination, the ESTs from the two libraries represent approximately 40% of genes expressed in late development, assuming that the non-redundant ESTs correspond to independent genes. They will provide a useful resource for investigating the genetic networks that regulate multicellular development of this organism.     

Growth inhibition and morphological changes of LLC-PK1 induced by ultimobranchial calcitonins

Ultimobranchial calcitonins (CTs), known to stimulate cAMP production, inhibited the growth of a porcine kidney cell line LLC-PK1. This inhibition was accompanied by degenerative changes including vacuole formation and cell detachment. The electron microscopic study revealed marked swelling of rough endoplasmic reticulum (RER). Other cAMP-increasing agents such as human CT, arginine, vasopressin, and forskolin showed less growth inhibitory activities and no induction of the degenerative changes. These results indicate that the growth inhibition of LLC-PK1 by ultimobranchial CTs is mainly due to cellular death caused by the swelling of RER via a signalling pathway other than the cAMP-dependent event(s).