Expression of Intermediate Filaments in the Balbiani Body and Ovarian Follicular Wall of the Japanese Quail (Coturnix japonica)

In the present study, we examined the distribution of 6 groups
ofintermediate filaments (IFs; cytokeratins, CKs, vimentin,
synemin,desmin, glial fibrillary acidic protein and lamins) in
oocytes andfollicular walls of the Japanese quail (Coturnix
japonica) during theirdevelopment using immunohistochemical and
ultrastructural techniques. Adistinctly vimentin- and
synemin-positive Balbiani body, which is atransient accumulation of
organelles (mitochondria, Golgi complex andendoplasnnic reticulum)
that occurs in the oocytes of all vertebratesincluding birds, could
be detected in the oocytes of primordial andearly pre-vitellogenic
follicles. In larger pre-vitellogenic follicles,the Balbiani body
has dispersed and the positivity of the granulosacells appeared to
concentrate in the basal portion of their cytoplasm.Our
ultrastructural data demonstrated that the matrix of the
Balbianibody consists of fine IFs, which may play a role in the
formation anddispersion of the Balbiani body. Of the CKs studied
(panCK, CK5, CK7,CK8, CK14, CK15, CK18 and CK19), only CK5 showed a
slight positivestaining in both the theca externa and the Balbiani
bodies ofpre-vitellogenic oocytes. In conclusion, our data, which
describe thechanges in avian IF protein expression during
folliculogenesis, suggestthat the functions of the IFs (vimentin
and synemin) of oocytes andfollicular walls are not primarily
mechanical but may be involved in thetransient tethering of
mitochondria in the area of the Balbiani body andin the gain of
endocrine competence during the differentiation ofgranulosa cells.