Mari Yokoyama, Yasuhiro Takegawa and Tadashi Yamashita
Ovaries are often found in pairs as part of the vertebrate female reproductive system that maintains immature egg cells until they become mature with ovulation. The ovary is also an internal secretion organ for both estrogen and progesterone. Estrogen is responsible for the appearance of secondary sex characteristics of females at puberty and for the maturation and maintenance of the reproductive organs. Progesterone functions mainly to regulate the condition of the endometrium, preparing it to accept a fertilized egg. On the other hand, glycans are a main component of the animal cell surface and show structural changes during early development and cell differentiation. In the present study, to clarify the relation between the changes in glycan structures and ovarian functions such as ovulation, we used a system in which ovulation was induced by sex hormone treatment. As a result, it was found that glycoproteins including terminal sialic acids, especially N-glycolyl neuraminic acid-type glycans, increased during development of the ovary. Furthermore, to find specific glycoproteins with the N-glycolyl neuraminic acid-type glycan that were induced by hormone treatment, we established a method for the purification of glycoproteins, using sialic acid followed by detection using mass spectrometry. Applying the modified protocol, transferrin could be detected as the protein that changed the amount of glycans in the developmental cycle of the ovary. Thus, this protocol will be a useful tool for the detection of glycoproteins with sialic acid residues. It may also be a valuable method for use with other organs.