In a recent study, we have used single-cell sensitive RT-PCR (retro transcriptase - polymerase chain reaction) technology and immunocytochemistry, to determine the timing of 1) gene expression of alpha6 and beta1 integrins, and of 2) localization of these integrin subunits on the plasma membrane in primordial germ cells and in oocytes during oogenesis (Zuccotti et al., 1998).

We found that both alpha6 and beta1 genes are expressed in female germ cells during all the stages of development analyzed, from 10.5 d.p.c. to 18.5 d.p.c., during oocyte growth and in ovulated eggs. The alternatively spliced isoform alpha6B is expressed from 10.5 d.p.c., whereas alpha6A begins to be expressed at 12.5 d.p.c., suggesting a different role for the two variants. In situ immunodetection of alpha6 or beta1 shows a ring of fluorescence on the female germ cell plasma membrane for both integrins at 10.5 d.p.c., then the fluorescent signal becomes undetectable at 12.5 d.p.c. to reappear again, this time with a patchy distribution, at 18.5 d.p.c.. This pattern of localization is maintained in oocytes isolated from newborn individuals and only when oocytes during growth reach the size of about 25-30 um in diameter the fluorescence becomes homogenous all around the whole oocyte surface.