Role of peanut-lectin-affinity molecules (PLAM) on primordial germ cells in the initial determination of sex in anura.

Peanut lectin (PNA) or N-acetylgalactosamine (galNA, a part of the disaccharide unit which is recognized by PNA) was injected into the coelomic cavity of anuran larvae at the developmental stages during which the genital ridges were growing, and the effect of these compounds on the initial determination of gonadal sex was examined. The treatment with PNA tended to inhibit (or perturb) the expression of feminizing gene(s) in Rana japonica, and of both feminizing and masculinizing genes in R. nigromaculata. In contrast, treatment with galNA suppressed the expression of masculinizing gene(s) considerably. In terms of the initial determination of gonadal sex during normal development, these results suggest that the PNA-affinity molecule (PLAM) of primordial germ cells acts as a trigger for the expression of genes that control sexual differentiation of somatic cells. Furthermore, the somatic cells (perhaps mesenchymal and/or epithelial cells), which respond to the stimulus via the PLAM of primordial germ cells, may differ in terms of the threshold for such a response between genetic males and females. This result suggests the mesenchymal and/or epithelial cells are not sexually predetermined, but rather that sexual determination follows the response to some signal(s) mediated by the PLAM.