TITLE:
Expression of a Testis-Specific Nuclear Protein, TRA98, in Mouse Testis during Spermatogenesis. A Quantitative and Qualitative Immunoelectron Microscopy (IEM) Analysis
AUTHORS:
Natsuki Inoue, Yuko Onohara, Sadaki Yokota
KEYWORDS:
Nuclear Protein, TRA98, Testis, Stage Cycle, Immunocytochemistry
JOURNAL NAME:
CellBio,
Vol.1 No.1,
April
2,
2013
ABSTRACT: TRA98 is a
testis-specific nuclear protein, but its biological role is unclear. We
analyzed the localization of TRA98 indeveloping spermatogenic cells using immunofluorescence (IF) and immunoelectron
microscopy (IEM). TRA98 was localized exclusively to the nuclei. In
spermatocytes, IF staining was associated with certain sub-nuclear structures to show a reticular pattern; the XY body
was strongly stained. In spermatids, both reticular and punctate staining
patterns were observed. In late spermatids, staining decreased as cell differentiation
proceeded. However, epididymal sperm were strongly stained when smear
preparations were not fixed, or followed by treatment with4 Murea or 2% mercaptoethanol. IEM
showed that gold signals were closely associated with electron-dense masses but
not with the nucleoli. We then investigated the expression of TRA98 indifferentiating spermatocytes
using a quantitative IEM technique. A small expression peak was observed around
stage II-III and a second large peak was noted at stage XI. In spermatids, a
single expression peak was observed at step 5; labeling density then decreased gradually but did not reach
zero. In early spermatids, heterochromatin was stained much more than
euchromatin. The results suggest that the function of TRA98 increases at three
points during spermatogenesis. In addition, TRA98 is maintained in the sperm
head and carried into the egg after fertilization.