Pregnancy-associated CA125 antigen as mucin: evaluation of ferning morphology

CA125 antigen is a high molecular mass, structurally heterogeneous, mucin-type molecule expressed during embryonic development as well as in adult human tissues. This study was aimed at investigating its mucin-related property of ferning, as a general complementary way of characterization. Pregnancy-associated CA125 antigen (pCA125) was examined using light, transmission and scanning electron microscopy and compared with cancer-derived CA125 antigen (cCA125). The results obtained for spread-out, air-dried pCA125 and cCA125 samples revealed clear differences in the patterns of crystalline as well as amorphous material. Thus, the fern-like crystals were mainly sparsely distributed and their morphology was atypical. The extent of crystallization of pCA125 was moderately lower than that of cCA125 antigen, whereas variation in the size and spatial organization of fern crystals was evident. Besides the material with a crystalline appearance, differences in the organic substrate were also noticeable. In contrast to the sponge-like appearance of pCA125, cCA125 had a more compact structure. These initial data may be relevant for relating biochemical properties of CA125 antigen with its morphology as a basis for elucidating its still obscure function under different physiological conditions.