Alastalo T P, Lönnström M, Leppä S, Kaarniranta K, Pelto-Huikko M, Sistonen L, Parvinen M
Department of Anatomy, University of Turku, Finland.
Exp Cell Res. 1998 Apr 10;240(1):16-27. doi: 10.1006/excr.1997.3926.
Heat shock transcription factors (HSFs) are generally known as regulators of cellular stress response. The mammalian HSF1 functions as a classical stress factor, whereas HSF2 is active during certain developmental processes, including embryogenesis and spermatogenesis. In the present study, we examined HSF2 expression at specific stages of the rat seminiferous epithelial cycle. We found that expression of the alternatively spliced HSF2-alpha and HSF2-beta isoforms is developmentally regulated in a stage-specific manner. Studies on cellular localization demonstrated that HSF2 is present in the nuclei of early pachytene spermatocytes at stages I-IV and in the nuclei of round spermatids at stages V-VIIab. In contrast a strong HSF2 immunoreactivity was detected in small distinct cytoplasmic regions from zygotene spermatocytes to maturation phase spermatids. Immunoelectron microscopic analysis revealed that these structures are mainly cytoplasmic bridges between germ cells. Our results on cellular localization of HSF2 and stage-specific expression of the HSF2 isoforms indicate that HSF2, in addition to its function as a nuclear transcription factor, may be involved in other cellular processes during spermatogenesis, possibly in the sharing process of gene products between the germ cells.
热休克转录因子（HSFs）通常被认为是细胞应激反应的调节因子。哺乳动物的HSF1作为一种典型的应激因子发挥作用，而HSF2在某些发育过程中具有活性，包括胚胎发生和精子发生。在本研究中，我们检测了大鼠生精上皮周期特定阶段的HSF2表达。我们发现，选择性剪接的HSF2-α和HSF2-β异构体的表达在发育过程中以阶段特异性方式受到调控。细胞定位研究表明，HSF2存在于I-IV期早期粗线期精母细胞的细胞核中，以及V-VIIab期圆形精子细胞的细胞核中。相反，从偶线期精母细胞到成熟阶段精子细胞，在小的离散细胞质区域检测到强烈的HSF2免疫反应性。免疫电子显微镜分析显示，这些结构主要是生殖细胞之间的细胞质桥。我们关于HSF2细胞定位和HSF2异构体阶段特异性表达的结果表明，HSF2除了作为核转录因子发挥功能外，可能还参与精子发生过程中的其他细胞过程，可能参与生殖细胞之间基因产物的共享过程。
