Abstract
Heat shock factor 1 (HSF1) is an important transcription factor in cellular stress responses, cancer, aging, and developmental processes including gametogenesis. Disruption of Hsf1, together with another HSF family member, Hsf2, causes male sterility and complete lack of mature sperm in mice, but the specific role of HSF1 in spermatogenesis has remained unclear. Here, we show that HSF1 is transiently expressed in meiotic spermatocytes and haploid round spermatids in mouse testis. The Hsf1−/− male mice displayed regions of seminiferous tubules containing only spermatogonia and increased morphological abnormalities in sperm heads. In search for HSF1 target genes, we identified 742 putative promoters in mouse testis. Among them, the sex chromosomal multicopy genes that are expressed in postmeiotic cells were occupied by HSF1. Given that the sex chromatin mostly is repressed during and after meiosis, it is remarkable that HSF1 directly regulates the transcription of sex-linked multicopy genes during postmeiotic repression. In addition, our results show that HSF1 localizes to the sex body prior to the meiotic divisions and to the sex chromocenter after completed meiosis. To the best of our knowledge, HSF1 is the first known transcription factor found at the repressed sex chromatin during meiosis.
Highlights
Could mask the incompletely synapsed X and Y chromosomes from meiotic surveillance mechanisms [2,3,4]
Heat shock factor 1 (HSF1) Is Transiently Expressed in Spermatocytes and Round Speramplicons were labeled with Cy5 dye, and the total input ampli- matids—It has been reported previously that in mice kept cons were labeled with Cy3 dye and under normal physiological conditions, HSF1 is expressed in all cohybridized to high density oligonucleotide tiling arrays. testicular cells [24]
The two-channel raw data were normalized between chan- tigated HSF1 expression in mouse testis, where the cycle of the nels with the Lowess normalization method and ChIP-to-input seminiferous epithelium is composed of 12 stages (I–XII), each log2 ratios were produced separately from all three replicates
Summary
Mice—Hsf knock-out mice were maintained in a mixed genetic background bred from a congenic stock (C57BL/6J; Hsf1) intercrossed with BALB/c, and they have been described previously [31]. Histology—Whole WT and Hsf1Ϫ/Ϫ testes were fixed in 4% paraformaldehyde overnight, embedded in paraffin, and cut into 4-m sections. Analysis of Sperm Head Morphology—Adult WT and Hsf1Ϫ/Ϫ male cauda epididymes were isolated, and sperm head morphology was classified into groups of normal, slightly abnormal, and grossly abnormal, as described earlier [35]. ChIP—Testes were isolated from adult WT mice and lysed in 4 ml of buffer, and the ChIP assays for the ChIP-chip screen were performed as described earlier [36]. All reactions were made in triplicate, using samples derived from at least three biological repeats These primers and probes were used: Sly (F, 5Ј-att caa tga aga aaa aga aaa atc agt-3Ј; R, 5Ј-cca tgg act tct atg cat tt-3Ј; probe (P), 5Ј-Fam gga agc ag. Unpaired Student’s t test was used for calculation of the p value in comparisons between WT and Hsf1Ϫ/Ϫ
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