Diagnosing cellular defects in an unexplained case of total fertilization failure.

Despite the advent of ICSI, cases of total fertilization failure (TFF) often lead to cycle cancellation with limited diagnostic and therapeutic strategies currently available. We report on the case of an infertile couple who failed to conceive after repeated IVF and ICSI. Sperm of the husband were morphologically normal and passed a functional test assessing their ability to activate mouse oocytes. Whether oocytes were activated artificially with calcium ionophore after injection of husband's or with donor sperm, all oocytes failed to fertilize. Multiple polar bodies and two disorganized spindle structures were predominantly observed, pointing towards a cytoplasmic defect in the oocytes as the primary cause of the couple's infertility. In fact, injection of husband's sperm into donor oocytes resulted in the delivery of healthy twins. This report describes a course of action that may be applied for couples with TFF after both IVF and ICSI.

Mouse sperm desiccated and stored in trehalose medium without freezing.

Mouse sperm with and without trehalose were desiccated under nitrogen gas and stored at 4 degrees C and 22 degrees C. After rehydration, sperm were injected into oocytes using intracytoplasmic sperm injection and embryonic development was followed. Sperm were dried for 5.0, 6.25, or 7.5 min, stored at 22 degrees C for 1 wk with and without trehalose. The percentages of blastocysts that developed from sperm with trehalose were 51%, 31%, and 20%, respectively, which was significantly higher than sperm without trehalose (10%, 3%, and 5%, respectively). Desiccation and storage in medium with trehalose significantly increased sperm developmental potential compared to medium without trehalose. Sperm dried for 5 min produced more blastocysts than sperm dried for 6.25 or 7.5 min. When sperm were dried in trehalose for 5 min and stored for 1 wk, 2 wk, 1 mo, or 3 mo at 4 degrees C, the percentages of blastocysts were 73%, 84%, 63%, and 39%; whereas those stored at 22 degrees C for 1 wk, 2 wk, or 1 mo were significantly lower (53%, 17%, and 6%, respectively). Embryos from sperm partially desiccated in trehalose for 5 min and stored at 4 degrees C for 1 or 3 mo were transferred to 10 pseudopregnant recipients. Implantation rates were 81% and 48%; live fetuses were 26% and 5%, respectively. One of the recipients delivered three live fetuses. The results show that trehalose has a significant beneficial effect in preserving the developmental potential of mouse sperm following partial desiccation and storage at temperatures above freezing.

Intracytoplasmic sperm injection (ICSI) enables rescue of valuable mutant mouse strains.

Genetically altered mice are important research tools for the study of human development and disease. Occasionally, whether or not related to the genetic mutation, mice may become infertile with age and, thus, risk loss of the mutant line. Under conditions in which assisted reproduction techniques (ARTs), such as in vitro fertilization, are unsuccessful, a new strategy, intracytoplasmic sperm injection (ICSI), may be applicable. This technique has been perfected for use in the mouse and is now considered a reliable, effective, and efficient ART. In the study reported here, we "rescued" (i.e., produced offspring, using ICSI from a "last-of-line" mutant male mouse) four lines that otherwise had become infertile and unresponsive to conventional ART's. A total of 26 live pups were produced from eight pregnant recipient foster mothers. Five mutant male mice were derived (one each from three lines, and two from one line), and all survived to adulthood. We found that live born mice could be successfully derived by use of ICSI that subsequently could breed by natural mating to reestablish the mutant line. Because of its effectiveness and reliability under these conditions, ICSI should be considered a powerful addition to the armamentarium of ART's applicable in the genetically-altered mouse, especially when only one male may still be available.

Desiccation tolerance of spermatozoa dried at ambient temperature: production of fetal mice.

Long-term preservation of mouse sperm by desiccation is economically and logistically attractive. The current investigation is a feasibility study of the preservation of mouse sperm by convective drying in an inert gas (nitrogen). Mouse sperm from the B6D2F1 strain isolated in an EGTA-supplemented Tris-HCl buffer were dried using three different drying rates and were stored for 18-24 h at 4 degrees C. The mean final moisture content was <5% for all the protocols. After intracytoplasmic sperm injection (ICSI), the mean blastocyst formation rates were 64%, 58%, and 35% using the rapid-, moderate-, and slow-drying protocols, respectively. The slow-drying protocol resulted in a rate of development significantly lower than that observed using rapid- and moderate-drying protocols and indicated that a slower drying rate may be detrimental to the DNA integrity of mouse sperm. The transfer of 85 two- or four-cell embryos that were produced using rapidly desiccated sperm resulted in 11 fetuses (13%) on Day 15 compared with the production of 34 fetuses (40%) produced using the transfer of 86 two- or four-cell embryos that were produced using fresh sperm (P < 0.05). The results demonstrate the feasibility of using a convective drying protocol for the successful desiccation of mouse sperm and identifies some of the important parameters required for optimization of the procedure.

Lyn tyrosine kinase inhibits nuclear export of the p53 tumor suppressor.

The p53 tumor suppressor is activated in the cellular response to stress. Mdm2 inhibits p53-dependent transactivation and promotes degradation of p53 by the ubiquitin-proteosome pathway. The present studies demonstrate that p53 binds directly to the nuclear Lyn tyrosine kinase. Lyn increases p53 levels and stimulates p53-mediated transcription by a kinase-independent mechanism. The results also demonstrate that Lyn increases nuclear levels of ubiquitinated p53 by inhibiting export of p53 to the cytoplasm. In concert with these results, Lyn reverses Mdm2-mediated degradation of p53 and increases p53-dependent apoptosis. Our findings support a previously undefined role for nuclear Lyn in both activation and Mdm2-mediated regulation of p53.