[
International C. elegans Meeting,
2001]
BAF is an essential, novel DNA-bridging protein of unknown function. We are using C. elegans to determine BAF's function in vivo , and to understand its interactions with a family of inner nuclear membrane proteins termed LEM-domain proteins. The LEM-domain proteins that are conserved in C. elegans include MAN1 and emerin, loss of which causes Emery-Dreifuss muscular dystrophy in humans. To test the hypothesis that BAF interacts with LEM-domain proteins, we stained C. elegans embryos by direct immunofluorescence using BAF-specific antibodies. Endogenous ceBAF is distributed along the nuclear rim, consistent with its association with inner membrane proteins. However, there appeared to be additional BAF staining in the nuclear interior. By double-staining for BAF plus either MAN1, emerin, or lamins in C. elegans embryos, we found that BAF colocalizes at the nuclear envelope with MAN1 and emerin, and that BAF colocalizes with lamins both at the perimeter and interior of the nucleus. These results support our hypothesis, and suggest that BAF is intimately associated with the nuclear lamina. The RNAi phenotype for BAF is early embryonic lethality associated with chromatin defects such as DNA bridging, super-condensation and perhaps nuclear fragmentation. These phenotypes suggest an essential role for BAF in chromatin decondensation and perhaps chromosome segregation.