While C. elegans oocytes do not have a thick cumulus layer or zona pellucida as in mammals, the nematode egg surface is coated with similar O-linked glycoproteins. PNA lectin and anti-chondroitin antibody staining show strong reactivity for both mucin-type and proteoglycan-type sugars. O-glycanase treatment specifically eliminates the PNA staining pattern, indicating that the predominant egg coat glycoproteins are modified with galactose-<font face=symbol>b</font>1,3-GalNac-O-serine/threonine. The role of mucin-type sugars in oogenesis was evaluated using mutants in polypeptide GalNAc transferases (ppGaNTases), which modify serine and threonine side chains of mucin-type glycoproteins. While deletion mutants in
gly-5, -6, -7, -8, -9, -10, -11 did not impair oogenesis, a null mutation in the ppGaNTase
gly-3 resulted in hermaphrodite sterility. When
gly-3-deficient L4 larva molt into adults, the gonad shape and DTC is normal. PNA lectin staining shows that both wild type and
gly-3 L4 larva and very young adults express a similar pattern of mucin-type glycoproteins in both the distal tip cell and germ cells. As adults mature in the first two days of adulthood, wild type germ cell migrate from the center core of the gonad to the edge, forming a cylindrical arrangement of germline nuclei and an open core of cytoplasmic material. This morphogenetic process is accompanied by an elevated expression of mucin-type sugars on the apical and lateral membranes of germ cells. However, in two-day old
gly-3 hermaphrodites, the gonads lack the elevated expression of mucin-type sugars on the germ cell surface and the natural morphogenetic change of
gly-3 germ cells is lost. By the second day of adulthood,
gly-3 gonads begin to loose some of their structural integrity, germ cells begin to budding off the sides of the gonads, and occasionally extend extra gonad arms. As the
gly-3 animals develop from two to three-day old adults a greater percentage of germ cells enter into meiosis; however, oocytes do not form and oocyte markers (J67 and PNA reactivity) are not expressed. Instead, the meiotic cells experience nuclear compaction and lead to an over-abundance of spermatid-like cells. Anti-SP56 antibody staining shows that
gly-3 gonads are masculinized by the second and third day of adulthood and high levels of ectopic sperm protein expression extends far into the distal germ cells at a time when SP56 protein production is normally shut down in wild type adults. Consequently, mucin-type glycosylation is required for morphogenetic movements of germ cells, the structural integrity of the gonads, and maintenance of genetic signals for mitotic cell division and the gender switch of the adult gonad.