A rat H1t‐GFP transgene recapitulates endogenous H1t expression pattern in mouse

H1 histones bind to linker DNA. H1t (H1f6), a testis‐specific linker histone variant, is present in pachytene spermatocytes and spermatids. The expression of H1t histone coincides with the acquisition of metaphase I competence in pachytene spermatocytes. Here we report the generation of H1t‐GFP transgenic mice. The H1t‐GFP (H1 histone testis‐green fluorescence protein) fusion protein expression recapitulates the endogenous H1t expression pattern. This protein appears first in mid pachytene spermatocytes in stage V seminiferous tubules, persists in round spermatids and elongating spermatids, but is absent in elongated spermatids. The strong green fluorescence signal, due to the high abundance of H1t‐GFP, is maintained in spermatocytes after induction towards metaphase I through treatment with okadaic acid. Therefore, H1t‐GFP can be used as a visual marker for monitoring the progression of meiosis in vitro and in vivo, as well as fluorescence‐activated cell sorting (FACS) sorting of germ cells.     

Histone H1t is not replaced by H1.1 or H1.2 in pachytene spermatocytes or spermatids of H1t-deficient mice

The linker histone gene H1t is exclusively expressed in the mammalian testis. In former experiments we have shown that H1.1 and H1.2 histone gene expression is significantly enhanced in testis of adult H1t deficient mice. In this report we have quantified the mRNA of different H1 genes in 9-day- and 20-day-old wild type and H1t knock out mice. In addition, we have analysed the distribution of H1.1 and H1.2 protein by immunofluorescent staining in spread male germ cells. The aim of this work was to answer the question whether H1t can be replaced during spermatogenesis by H1.1 or H1.2. In our experiments we could not detect elevated levels of H1.1 or H1.2 in pachytene spermatocytes or haploid cells of H1t deficient testis. Therefore, in these cells, H1t seems not to be replaced by H1.1 or H1.2.     

CD1d induction in solid tumor cells by histone deacetylase inhibitors through inhibition of HDAC1/2 and activation of Sp1

CD1d is a MHC class-like molecule that presents glycolipids to natural killer T (NKT) cells, then regulates innate and adaptive immunity. The regulation of CD1d gene expression in solid tumors is still largely unknown. Gene expression can be epigenetically regulated by DNA methylation and histone acetylation. We found that histone deacetylase inhibitors, trichostatin A (TSA) and suberoylanilide hydroxamic acid (SAHA), induced CD1d gene expression in human (A549 and NCI-H292) and mouse (TC-1 and B16/F0) cancer cells. Simultaneous knockdown of HDAC1 and 2 induced CD1d gene expression. Sp1 inhibitor mitramycin A (MTM) blocked TSA- and SAHA-induced CD1d mRNA expression and Sp1 luciferase activity. Co-transfection of GAL4-Sp1 and Fc-luciferase reporters demonstrated that TSA and SAHA induced Sp1 luciferase reporter activity by enhancing Sp1 transactivation activity. The binding of Sp1 to CD1d promoter and histone H3 acetylation on Sp1 sites were increased by TSA and SAHA. These results indicate that TSA and SAHA could up-regulate CD1d expression in tumor cells through inhibition of HDAC1/2 and activation of Sp1.