Multiple Synaptonemal Complexes (Polycomplexes) in Wild-Type Hermaphroditic Caenorhabditis elegans and their absence in males.
Abstract
Multiple synaptonemal complexes (polycomplexes) (PC) are similar in structure to synaptonemal complexes (SC) and are also highly conserved through evolution. They have been described in over 70 organisms throughout all life forms, and in other nematodes. Extranuclear Fibrillar Material (FM) is observed adjacent to the nuclear envelope at leptotene and zygotene, forms into PCs, contributes to the formation of the SCs, and the attachment of the telomeres of the chromosomes. The existence of PCs in XX Wild-type hermaphrodites of C. elegans, as well as other organisms, are restricted to meiotic and germ-line derived tissues. Although PCs may be present prior to or after SC formation in other nematodes, e.g. Ascaris, their formation and function are different at each stage. In C. elegans, PCs were observed only prior to pachytene, at the leptotene/zygotene interface, and disappeared afterwards. The structure and biochemical composition of PCs is similar to SCs such that the basic unit is tripartite, consisting of two lateral elements and a central region, within which transverse elements exist. The SYP-1 protein, localized in the central element of SCS in C. elegans, along with HTP-1 and HAL-2, are integral to the highly organized structure of the polycomplexes. Polycomplexes were not observed in the XO male reproductive form of C. elegans , inferring different levels of control of the pairing of homologous chromosomes and attachment to the nuclear envelope during meiotic prophase.