What leads from dead-end?

In vitro fertility rate of 129 strain is improved by buserelin (gonadotropin-releasing hormone) administration prior to superovulation

The 129 mice are well recognized for their low fertility and it is speculated that this lack of fertility may be due to the oocyte condition. In this study we investigated superovulation regimens for the 129S1/SvImJ mouse strain to improve the oocyte quality and fertility rate of in vitro fertilization (IVF). Female mice were divided into four groups based on hormone and timing of injection. Group 1 received pregnant mare serum gonadotropin (PMSG) and 48 h later human chorionic gonadotropin (hCG); using the same dose, group 2 received hCG 52 h post-PMSG and group 3, 55 h post-PMSG. Group 4 received buserelin (gonadotropin-releasing hormone agonist [GnRH]) followed 24 h later by PMSG and then hCG 55 h post-PMSG. IVF was performed using 129S1/SvImJ oocytes and sperm; C57BL/6J sperm with 129S1/SvImJ oocytes was used as fertility control. The IVF fertility rate was 1% (Groups 1 and 2), 17% (Group 3) and 55% (Group 4) for 129 oocytes fertilized with 129 sperm. For 129 oocytes fertilized with C57BL/6J sperm, the fertility rate was 5% (Group 1), 10% (Group 2), 40% (Group 3) and 59% (Group 4). These results suggest that extending the interval time between PMSG and hCG and giving GnRH in addition to the standard PMSG and hCG treatments can improve IVF fertility rate of 129S1/SvImJ mouse strains significantly.

Review of MicroRNA Proposed Target Genes in Oral Cancer. Part II

Objectives

Cancer is the product of alterations in oncogenes, tumour suppressor genes and most recently microRNA genes not as a single event or single change but rather as a multistep process. The role of microRNA genes in carcinogenesis is recently explored and appears to be an early event in the pathogenesis of this as well as other disease processes and occurs via gene regulation by their own products, the microRNAs. The purpose of this article was to review the literature concerning MicroRNA proposed target genes in oral cancer.

Material and Methods

A review of the available literature from 2000 to 2011 regarding the potential roles assumed by microRNAs in oral cancer was undertaken using PubMed, Medline, Scholar Google and Scopus. Keywords for the search were: microRNA and oral cancer and target genes, microRNA deregulation and oral cancer, microRNA and carcinogenesis in the head and neck/oral cavity. English language full length articles were reviewed.

Results

Several microRNAs deregulated in oral cancer have been functionally validated and their exact target genes have been identified. Furthermore the carcinogenesis pathways impacted by these alterations has been proposed for some of these microRNAs.

Conclusions

The expanding knowledge of specific roles of certain microRNAs is further contributing to our understanding of the complexity of tumour progression and behaviour. Consideration of this information and incorporation into treatment modalities through targeted therapy could potentially enhance our abilities to improve outcome especially when other established therapies have failed.

Accelerated modification of the zona pellucida is the primary cause of decreased fertilizability of oocytes in the 129 inbred mouse strain

We investigated whether the small litter size in the 129 inbred mouse strain results from a reduction in oocyte fertilizability. Sensitivity of the zona pellucida to α-chymotrypsin was examined for oocytes collected at 14 h (shortly after ovulation), 17 h, and 20 h after hCG injection. Passage of spermatozoa through the zona pellucida (using an in vitro fertilization (IVF) technique) and the density of cortical granules were examined for oocytes collected at 14 and 17 h after hCG injection. The capability of the oolemma to fuse with the sperm plasma membrane was also evaluated by IVF using zona-free eggs. The zona pellucida became markedly resistant to the enzyme 17 h after hCG injection. IVF rates significantly decreased at this time. In addition, there was a significant reduction in the density of cortical granules. When zona-free oocytes were inseminated, high fertilization rates were obtained at both 17 and 14 h after hCG injection. These results indicate that accelerated modification of the zona pellucida primarily causes a decreased fertilizability of oocytes in 129 mice, resulting in the low reproductive performance of this strain.

MicroRNA-24 targeting RNA-binding protein DND1 in tongue squamous cell carcinoma

Deregulations of microRNA have been frequently observed in tongue squamous cell carcinoma (TSCC), but their roles in tumorigenesis are not entirely clear. Here, we reported the up-regulation of miR-24 in TSCC. MiR-24 up-regulation reduced the expression of RNA-binding protein dead end 1 (DND1). Knockdown of miR-24 led to enhanced expression of DND1. The direct targeting of miR-24 to the DND1 mRNA was predicted bioinformatically and confirmed by luciferase reporter gene assays. Furthermore, the miR-24-mediated change in DND1 expression suppressed the expression of cyclin-dependent kinase inhibitor 1B (CDKN1B), and also led to enhanced proliferation and reduced apoptosis in TSCC cells.

Low fertility in vivo resulting from female factors causes small litter size in 129 inbred mice

Purpose

129 inbred mice show poor reproductive ability, as evidenced by small litters; however, the exact cause of this is unknown. In the present in vivo study we examined fertility and subsequent post-implantation development in an attempt to clarify the cause of small litter size in 129 mice.

Methods

129 or C57BL/6J females that displayed vaginal plugs 1 day after mating with males of the same strain were examined for the presence of fertilized eggs. Reciprocal matings were also performed between 129 and C57BL/6J mice. Subsequent post-implantation development of fertilized eggs was examined by dissecting females 18-19 days after the vaginal plugs were found.

Results

Mean numbers of recovered eggs were 7.9 and 8.0 in 129 and C57BL/6J mice, respectively. Half of the recovered eggs were unfertilized in 129 mice, whereas all were fertilized in C57BL/6J mice. Mean numbers of live fetuses 18-19 days after mating were significantly lower in 129 mice (4.7) than in C57BL/6J mice (7.3). In different types of pairings using both strains of mice, the fertility was significantly lower whenever 129 females were used.

Conclusions

The small litter size in 129 mice is caused by low fertility resulting from female factors.

Mouse apolipoprotein B editing complex 3 (APOBEC3) is expressed in germ cells and interacts with dead-end (DND1)

BACKGROUND

The dead-end (Dnd1) gene is essential for maintaining the viability of germ cells. Inactivation of Dnd1 results in sterility and testicular tumors. The Dnd1 encoded protein, DND1, is able to bind to the 3'-untranslated region (UTR) of messenger RNAs (mRNAs) to displace micro-RNA (miRNA) interaction with mRNA. Thus, one function of DND1 is to prevent miRNA mediated repression of mRNA. We report that DND1 interacts specifically with APOBEC3. APOBEC3 is a multi-functional protein. It inhibits retroviral replication. In addition, recent studies show that APOBEC3 interacts with cellular RNA-binding proteins and to mRNA to inhibit miRNA-mediated repression of mRNA.

METHODOLOGY/PRINCIPAL FINDINGS

Here we show that DND1 specifically interacts with another cellular protein, APOBEC3. We present our data which shows that DND1 co-immunoprecipitates APOBEC3 from mammalian cells and also endogenous APOBEC3 from mouse gonads. Whether the two proteins interact directly remains to be elucidated. We show that both DND1 and APOBEC3 are expressed in germ cells and in the early gonads of mouse embryo. Expression of fluorescently-tagged DND1 and APOBEC3 indicate they localize to the cytoplasm and when DND1 and APOBEC3 are expressed together in cells, they sequester near peri-nuclear sites.

CONCLUSIONS/SIGNIFICANCE

The 3'-UTR of mRNAs generally encode multiple miRNA binding sites as well as binding sites for a variety of RNA binding proteins. In light of our findings of DND1-APOBEC3 interaction and taking into consideration reports that DND1 and APOBEC3 bind to mRNA to inhibit miRNA mediated repression, our studies implicate a possible role of DND1-APOBEC3 interaction in modulating miRNA-mediated mRNA repression. The interaction of DND1 and APOBEC3 could be one mechanism for maintaining viability of germ cells and for preventing germ cell tumor development.