FIGURE 1.

HSF1 is transiently expressed during mouse spermatogenesis. A, the localization and expression of HSF1 in specific cell types were examined by immunohistochemistry. Panels a and b, HSF1 immunostaining of wild-type (Hsf1 WT) and Hsf1 knock-out (Hsf1 KO) testis. No signal in the seminiferous epithelium of Hsf1 KO testis indicates specificity of the antibody. Panels c–h, HSF1 immunostaining (red) of WT testis, counterstained with Hoechst (blue). Representative stages are denoted by Roman numerals. Insets show blowups of the selected regions. SC, spermatocyte; RS, round spermatid; ES, elongating spermatid. Scale bars, 100 μm. B, Western blot analysis of HSF1 levels in Hsf1 WT and KO testis. Equal protein loading was assessed by β-tubulin and α-actin. C, a schematic drawing displaying the cell type-specific expression of HSF1 throughout the seminiferous epithelial cycle. Each vertical column, designated by a Roman numeral, depicts a stage of the seminiferous epithelial cycle and is comprised of a defined set of developing germ cells. In the schematic (C), the developmental progression of a cell is followed from the bottom row, left to right. The cycle ends with the release of morphologically mature sperm to the lumen of the tubule. The light absorption patterns of corresponding stages of the seminiferous tubule are shown at the bottom. Stages IX–XI, pale zone (PZ); stages XII–I, weak spot (WS); stages II–VI, strong spot (SS); and stages VII–VIII, dark zone (DZ).