The E3 Ubiquitin Ligase MIB-1 Is Necessary To Form the Nuclear Halo in Sperm.

Unlike the classical nuclear envelope with two membranes found in other eukaryotic cells, most nematode sperm nuclei are not encapsulated by membranes. Instead, they are surrounded by a nuclear halo of unknown composition. How the halo is formed and regulated is unknown. We used forward genetics to identify molecular lesions behind three classical (fertilization defective) mutations that disrupt the ultrastructure of the sperm nuclear halo. We found and alleles to be nonsense mutations in was caused by a nonsense mutation in GFP::MIB-1 was expressed in the germline during early spermatogenesis, but not in mature sperm. encodes a conserved E3 ubiquitin ligase homologous to vertebrate Mib1 and Mib2, which function in Notch signaling. Here, we show that is important for male sterility and is involved in the regulation or formation of the nuclear halo during nematode spermatogenesis.