Neurone differentiation in cell lineage mutants of Caenorhabditis elegans.

Abstract

The nematode Caenorhabditis elegans develops by an essentially invariant sequence of cell divisions1–3 leading to an adult complement of 959 somatic cells. In this organism cell fate is correlated with cell lineage, suggesting that genealogy may be a determining factor for the differentiated state of a cell. The study of mutants with altered cell lineages may help elucidate the precise mechanisms by which cell fate is decided. Several cell lineage mutants have been isolated and characterized4,5, some having more and some fewer cell divisions than wild type. We have now investigated the cell types produced by two cell lineage mutants; these mutants exhibit blocks in certain terminal or near terminal cell divisions, which in normal animals generally give rise to daughter cells that differentiate into distinctly different cell types. We find that the blocked cells in the mutants generally exhibit the differentiated characteristics of only one of the two daughter cells that normally would be produced. The differentiated state of the blocked precursors may be due to an intrinsic dominance of one cell type over another hi what is essentially a fused cell, and/or it may reveal the state of commitment of the precursor in wild-type animals.