Jensen et al. (1994) describe the primary structure, glycosylation and tissue localization of fetal antigen 1 isolated from second-trimester human amniotic fluid. FA1 is a single-chained, heterogeneous glycoprotein of 225-262 amino acid residues. FA1 has six well conserved epidermal-growth-factor motifs and contains up to ten O-glycosylation and N-glycosylation sites, six of which are differentially glycosylated. Alignment to the translated sequences of Mus. musculus dlk and human dlk revealed 86% and 99% identity, respectively, to a 259-amino-acid residue overlap, and this high similarity extends with minor corrections to the human adrenal-specific mRNA, pG2 as well. In 1997, Jensen et al. described an ELISA technique for quantification of FA1.
General function
Ligand, Hormone, Growth factor
Comment
Cellular localization
Secreted, Plasma membrane
Comment
FA1 is synthesized as a membrane anchored protein and released into the circulation after enzymic cleavage. Circulating FA1 represents the post-translationally modified gene product of human dlk which, in turn, is identical to human adrenal-specific mRNA pG2.
Ovarian function
Comment
Expression regulated by
Comment
Ovarian localization
Theca, Stromal cells
Comment
Immunohistochemical analysis of the ovary by Jensen et al. (1999) showed the presence of FA1 in the theca interna and the hilus cells hut not in the granulosa cells or the oocyte. In follicular fluid the concentration of FA1 was three times higher than that of serum.