Desialylation of core type 1 O-glycan in the equine embryonic capsule coincides with immobilization of the conceptus in the uterus

• Published in: Carbohydrate research 2007-06, Vol.342 (8), p.1110-1115
• Main Authors: Arar, Sharif, Chan, Kenneth H., Quinn, Bette A., Waelchli, Rudolf O., Hayes, M. Anthony, Betteridge, Keith J., Monteiro, Mario A.
• Format: Article
• Language: English
• Subjects: Animals; Carbohydrate Sequence; Chromatography, Gas; Core type 1; Embryonic capsule; Equine pregnancy; Female; Fertilization; Glycoproteins - chemistry; Horses; Mass spectrometry; Monosaccharides - analysis; O-Glycan; Polysaccharides - analysis; Polysaccharides - chemistry; Pregnancy; Sialic acid; Uterus - physiology
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2007.02.016

Equine embryo capsule during pre-fixation (mobile stage) expressed a sialylated core type 1: Neu5Ac-(2→3)-Gal-(1→3)-GalNAc Equine embryo capsule post-fixation (non-mobile stage) expressed a desialylated core type 1: Gal-(1→3)-GalNAc During the second and third weeks of pregnancy, the equine conceptus expands rapidly while it is enclosed within a glycan capsule. Around day 16 of gestation, the conceptus loses its mobility in the uterus by a process termed ‘fixation’, coinciding with various changes in the capsule. Here, we compared the structure of the carbohydrate moieties expressed by the capsule during pre- and post-fixation periods. The glycan structures were studied by chemical analyses in combination with mass spectrometry. Capsule material from conceptuses collected before fixation (days 13–16) was observed to carry a sialylated core type 1 O-linked glycan, Neu5Ac-(2→3)-Gal-(1→3)-GalNAc-(1→Ser/Thr. By comparison, analysis of post-fixation capsules (days 17–19) revealed a desialylated core type 1, Gal-(1→3)-GalNAc-(1→Ser/Thr. The equine embryonic capsule also furnished 4-substituted GlcNAc, 4-substituted Glc and 2,3,4,6-tetrasubstituted Glc residues, the concentrations of which did not change between pre- and post-fixation stages. The loss of sialic acid from the sialylated core type 1 in the capsule appears to be directly related to successful fixation of the conceptus, and thus critical to the continuance of pregnancy in horses.