[
International C. elegans Meeting,
2001]
Bag1 is a multifunctional protein that interacts with a variety of partner proteins. In mammalian cells, overexpression of Bag1 influences different signal transduction pathways, which in general leads to prevention of apoptosis or inhibition of cell cycle arrest. Interaction partners of Bag1 include Bcl-2, Raf-1 kinase, hormone receptors, and Hsp70. Bag1 enhances the anti-apoptotic function of Bcl-2, stimulates of the Raf-1 kinase activity, and inhibits Hsp70 chaperone activities. We are using C. elegans as a model to investigate the function of Bag1 during development and survival of a complex multicellular organism. We have created and analyzed a deletion mutant of Bag1 (F57B10.11). Null mutants appear similar to the wild type N2 strain with respect to viability, anatomy, timing of development, and life span. This indicates that Bag1 is not an essential gene and, moreover that Bag1 is not essential for Hsp70 activity under physiological conditions. Interestingly, the Bag1 null hermaphrodites show a 20% increase in the number of progeny compared to wild type N2 worms. Given the effect of overexpression of Bag1 on signal transduction pathways in mammalian cells, often reflected in changes in transcriptional activities, we asked whether phenotypic changes in C.elegans caused by deletion of Bag1 could be explained by changes in the mRNA expression profile. We are currently analyzing the mRNA expression profile of adult Bag1 null worms, compared to adult wild type N2 worms, using full genome microarrays. We will report on our progress on the microarray analysis and on the characterization of the phenotype of the Bag1 deletion strain.
[
International Worm Meeting,
2011]
Nematodes are well suited for a comparative study of early embryogenesis. Analyzing development of a single model system like Caenorhabditis elegans does not shed any light on the degree of evolutionary modifications within the taxon Nematoda. For better understanding evolution of development among nematodes including the identification of plesiomorphic and apomorphic characters, we compared early embryogenesis of representatives from all 12 nematode clades (phylogeny after Holterman et al., 2006; Mol. Biol. Evol. 23:1792-1800). Our data reveal that embryogenesis is unexpectedly variable with floating transitions that can be interpreted as frozen images of evolutionary change. Particularly, members of clade 1 and 2 differ massively from the standard C. elegans. Nevertheless, some basic developmental similarities appear to be common among all nematodes, e.g. the general existence of at least partial cell lineages and the influence of Polarity Organizing Centers (POCs). These POCs are required for generating a linear sequence of cells along the a-p axis which constitute the ventral midline. Depending on phylogenetic position fewer or more cells of this midline divide into left and right daughters this way establishing bilateral symmetry within individual lineages. Our studies reveal the stepwise emergence of founder cells and dramatic fate shifts during evolution. The comparison between embryogenesis of the basal nematode Tobrilus stefanskii and the tardigrade Hypsibius dujardini (Gabriel et al., 2007; Dev. Biol. 312, 545-59) with respect to the early cell division pattern revealed surprising similarities between these two. This may be considered as embryological support for the Ecdysozoa hypothesis.