Before fertilization, chromatins of both mouse oocytes and spermatozoa contain very few acetylated histones. Soon after fertilization, chromatins of both gametes become highly acetylated. The same deacetylation-reacetylation changes occur with histones of somatic nuclei transferred into enucleated oocytes. The significance of these events in somatic chromatin reprogramming to the totipotent state is not known. To investigate their importance in reprogramming, we injected cumulus cell nuclei into enucleated mouse oocytes and estimated the histone deacetylation dynamics with immunocytochemistry. Other reconstructed oocytes were cultured before and/or after activation in the presence of the highly potent histone deacetylase inhibitor trychostatin A (TSA) for up to 9 h postactivation. The potential of TSA-treated and untreated oocytes to develop to the blastocyst stage and to full term was compared. Global deacetylation of histones in the cumulus nuclei occurred between 1 and 3 h after injection. TSA inhibition of histone deacetylation did not affect the blastocyst rate (37% with and 34% without TSA treatment), whereas extension of the TSA treatment beyond the activation point significantly increased the blastocyst rate (up to 81% versus 40% without TSA treatment) and quality (on average, 59 versus 45 cells in day 4 blastocysts with and without TSA treatment, respectively). TSA treatment also slightly increased full-term development (from 0.8% to 2.8%). Thus, deacetylation of somatic histones is not important for reprogramming, and hyperacetylation might actually improve reprogramming.

Memory B cells are essential for generating rapid and robust secondary antibody responses. It has been thought that the unique cytoplasmic domain of IgG causes the prompt activation of antigen-experienced IgG memory B cells. To assess this model, we have generated a mouse containing IgG1 B cells that have never encountered antigen. We found that, upon challenge, antigen-experienced IgG1 memory B cells rapidly differentiated into plasma cells, whereas nonexperienced IgG1 B cells did not, suggesting the importance of the stimulation history. In addition, our results suggest that repression of the Bach2 transcription factor, which results from antigen experience, contributes to predisposition of IgG1 memory B cells to differentiate into plasma cells.

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Intracytoplasmic sperm injection (ICSI) in the human is a very effective procedure which allows the fertilization of the majority of oocytes even in cases of extreme oligoasthenoteratozoospermia. Round-headed acrosomeless human spermatozoa, however, form an exception to this rule, because in about half of the couples with globozoospermia all oocytes remain unfertilized after injection. The incapacity of the spermatozoon to activate the oocyte following injection of round-headed spermatozoa could be the underlying mechanism. To investigate this hypothesis, activation rates of mouse oocytes injected with spermatozoa from a patient with globozoospermia were compared with those obtained after injection with normal spermatozoa. Of mouse oocytes surviving the injection with donor spermatozoa, 95% underwent activation, compared to none of the 88 mouse oocytes surviving the injection with round-headed spermatozoa. After fixation, prematurely condensed sperm chromosomes were found in these oocytes. Parthenogenetic activation of mouse oocytes (8% ethanol at 40 min after injection) injected with round-headed spermatozoa led to the activation of 96% of oocytes. These oocytes developed normally to the first mitosis and were fixed for analysis of the sperm karyotypes. The incidence of chromosomal abnormalities of round-headed spermatozoa (6%) was similar to that in spermatozoa from a fertile donor (9%). These data provide further information on the basic defect in cases of globozoospermia and demonstrate that globozoospermia is not associated with sperm karyotype abnormalities.

NKT cells demonstrate antitumor activity when activated to produce Th1 cytokines by DCs loaded with α-galactosylceramide, the prototypic NKT cell-activating glycolipid antigen. However, most patients do not have sufficient numbers of NKT cells to induce an effective immune response in this context, indicating a need for a source of NKT cells that could be used to supplement the endogenous cell population. Induced pluripotent stem cells (iPSCs) hold tremendous potential for cell-replacement therapy, but whether it is possible to generate functionally competent NKT cells from iPSCs has not been rigorously assessed. In this study, we successfully derived iPSCs both from embryonic fibroblasts from mice harboring functional NKT cell-specific rearranged T cell receptor loci in the germline and from splenic NKT cells from WT adult mice. These iPSCs could be differentiated into NKT cells in vitro and secreted large amounts of the Th1 cytokine IFN-γ. Importantly, iPSC-derived NKT cells recapitulated the known adjuvant effects of natural NKT cells and suppressed tumor growth in vivo. These studies demonstrate the feasibility of expanding functionally competent NKT cells via an iPSC phase, an approach that may be adapted for NKT cell-targeted therapy in humans.