Expression of cell-cycle regulator CDK2-associating protein 1 (p12CDK2AP1) in transgenic mice induces testicular and ovarian atrophy in vivo

A mouse-specific retrotransposon drives a conserved Cdk2ap1 isoform essential for development

Retrotransposons mediate gene regulation in important developmental and pathological processes. Here, we characterized the transient retrotransposon induction during preimplantation development of eight mammals. Induced retrotransposons exhibit similar preimplantation profiles across species, conferring gene regulatory activities, particularly through long terminal repeat (LTR) retrotransposon promoters. A mouse-specific MT2B2 retrotransposon promoter generates an N-terminally truncated Cdk2ap1ΔN that peaks in preimplantation embryos and promotes proliferation. In contrast, the canonical Cdk2ap1 peaks in mid-gestation and represses cell proliferation. This MT2B2 promoter, whose deletion abolishes Cdk2ap1ΔN production, reduces cell proliferation and impairs embryo implantation, is developmentally essential. Intriguingly, Cdk2ap1ΔN is evolutionarily conserved in sequence and function yet is driven by different promoters across mammals. The distinct preimplantation Cdk2ap1ΔN expression in each mammalian species correlates with the duration of its preimplantation development. Hence, species-specific transposon promoters can yield evolutionarily conserved, alternative protein isoforms, bestowing them with new functions and species-specific expression to govern essential biological divergence.

MicroRNA-21 is involved in oocyte maturation, blastocyst formation, and pre-implantation embryo development

Follicular fluid is one source of microRNAs (miRNAs). These miRNAs originate from oocytes and their neighboring cells. The changes in the miRNAs profile in the follicular fluid could alter folliculogenesis and oocyte maturation, and lead to infertility. Polycystic ovary syndrome (PCOS) patients have increased miR-21 levels in their sera, granulosa cells, and follicular fluid, and this mi-RNA plays a role in the pathophysiology and follicular dysfunction of PCOS patients. In the current study, we intend to examine whether expression levels of miR-21 influence oocyte maturation and embryo development. We examined miR-21 over-expression and down-regulation of miR-21 by miR-off 21 during in vitro maturation (IVM) to assess its influence on oocyte maturation and embryo development in mice. Over-expression of miR-21 in cumulus cells decreased expansion, meiotic progression, Glutathione-S-transferase GSH levels, and decreased expressions of Bmpr2 and Ptx3 genes. Subsequently, we noted that in vitro fertilization, and the cleavage rate and blastocyst formation significantly increased in cumulus oocyte complexes (COCs) that over-expressed miR-21. Inhibition of miR-21 by miR-off 21 led to increased cumulus expansion and GSH levels, along with decreased cleavage rate and blastocyst formation by alterations in Cdk2ap1 and Oct4 gene expressions. However, oocyte progression from the germinal vesicle (GV) to the metaphase II (MII) stage was not significant. miR-21 altered the gene expression levels in cumulus cells and influenced cytoplasmic oocyte maturation, cumulus expansion, and subsequent embryonic development in mice.

Sonodelivery Facilitates Sustained Luciferase Expression from an Episomal Vector in Skeletal Muscle

Successful gene delivery to skeletal muscle is a desirable goal, not only for treating muscle diseases, but also for immunization, treatment of metabolic disorders, and/or delivering gene expression that can treat systemic conditions, such as bone metastatic cancer, for example. Although naked DNA uptake into skeletal muscle is possible, it is largely inefficient in the absence of additional chemical or physical delivery methods. We describe a system for delivery of non-viral or plasmid DNA to skeletal muscle using ultrasound-assisted sonoporation of a nanoplex combining plasmid DNA and a branched polymer based on poly(cyclooctene-graft-oligopeptide). The materials and methods described herein promise to advance the field of sonodelivery and of gene delivery to muscle for therapeutic applications since a simple system is presented that enables long-term gene expression in vivo with the promise of a minimal inflammatory gene expression profile.

Interleukin-27 gene delivery for modifying malignant interactions between prostate tumor and bone

We have examined the role of a novel cytokine, interleukin-27 (IL-27), in mediating interactions between prostate cancer and bone. IL-27 is the most recently characterized member of the family of heterodimeric IL-12-related cytokines and has shown promise in halting tumor growth and mediating tumor regression in several cancer models, including prostate cancer. Prostate cancer is frequently associated with metastases to the bone, where the tumor induces a vicious cycle of communication with osteoblasts and osteoclasts to induce bone lesions, which are a significant cause of pain and skeletal-related events for patients, including a high fracture risk. We describe our findings in the effects of IL-27 gene delivery on prostate cancer cells, osteoblasts, and osteoclasts at different stages of differentiation. We applied the IL-27 gene delivery protocol in vivo utilizing sonoporation (sonodelivery) with the goal of treating and reducing the growth of prostate cancer at a bone metastatic site in vivo. We used a new model of immune-competent prostate adenocarcinoma and characterized the tumor growth reduction, gene expression, and effector cellular profiles. Our results suggest that IL-27 can be effective in reducing tumor growth, can help normalize bone structure, and can promote enhanced accumulation of effector cells in prostate tumors. These results are promising, because they are relevant to developing a novel IL-27-based strategy that can treat both the tumor and the bone, by using this simple and effective sonodelivery method for treating prostate tumor bone metastases.

[Expression of cyclin-dependent kinase 2-associated protein 1 in chicken embryos of different sexes]

To investigate the expression and functions of cyclin-dependent kinase 2-associated protein 1 (cdk2ap1) screened by suppression subtractive hybridization in chicken embryo development, a pair of primers was designed to amplify the cdk2ap1 fragment by RT-PCR and subsequently the fragment obtained was cloned into the plasmid pGEM-T. Sense and antisense probes labeled with digoxigenin were generated using SP6 and T7 RNA polymerases, respectively, and used to examine cdk2ap1 expression in chicken embryos of both sexes by whole-mount in situ hybridization. In both sexes, cdk2ap1 was expressed in the head mesenchyme, rhombencephalon, optic vesicles, spinal neural tube, and forelimb of 4.0-day-old embryos and the expression in males was significantly higher than that in females. In addition, in the genital ridge and hindlimb of the 4.0-day-old chicken embryo, cdk2ap1 was obviously expressed in the males but not in females. It is supposed that cdk2ap1 may play a role in the sexual differentiation and development of gonad of chicken embryo.

Isolation and characterization of sexual dimorphism genes expressed in chicken embryonic gonads

In chicken, the bipotential embryonic gonad differentiates into either a pair of testes or an ovary, but few genes that underlying the gonadal sex differentiation have been identified and the sex-determination gene is still unknown. To identify more genes involved in chicken sex differentiation, we employed suppression subtractive hybridization to isolate differentially expressed genes between sexes from chicken gonads during a period of E3.5-E6. A total of 152 cDNA clones corresponding to 88 genes (41 from F-M library and 47 from M-F library) were screened using dot-blot analysis. These genes are located mainly on the macrochromosomes (1-5) with five in the sex chromosomes (one in W and four in Z), encoding four dominating molecular categories belonging to enzyme, DNA association, RNA association, and structural protein. Comparing the obtained cDNA sequences with those in chicken EST database, it showed that cDNAs of 32 genes from F-M library and 16 from M-F library have homologs in two reported embryonic gonad cDNA libraries. Quantitative real-time PCR analysis of eight genes involved in epigenetic and transcription regulation showed significantly different expression between sexes of CDK2AP1, SMARCE1, SAP18, SUDS3, and PQBP1 appeared at the early stage in gonad development (E4). Based on the functional comparison of sexual differentially expressed genes, the roles of some putatively important genes including ATP5A1W, CDK2AP1, mitochondrial transcripts, etc. have been analyzed. In conclusion, characterization of isolated genes would provide valuable clues to identify potential candidates involved in genetic mechanisms of chicken sex differentiation and gonad development.

Targeted inactivation of p12, CDK2 associating protein 1, leads to early embryonic lethality

Targeted disruption of murine Cdk2ap1, an inhibitor of CDK2 function and hence G1/S transition, results in the embryonic lethality with a high penetration rate. Detailed timed pregnancy analysis of embryos showed that the lethality occurred between embryonic day 3.5 pc and 5.5 pc, a period of implantation and early development of implanted embryos. Two homozygous knockout mice that survived to term showed identical craniofacial defect, including a short snout and a round forehead. Examination of craniofacial morphology by measuring Snout Length (SL) vs. Face Width (FW) showed that the Cdk2ap1(+/-) mice were born with a reduced SL/FW ratio compared to the Cdk2ap1(+/+) and the reduction was more pronounced in Cdk2ap1(-/-) mice. A transgenic rescue of the lethality was attempted by crossing Cdk2ap1(+/-) animals with K14-Cdk2ap1 transgenic mice. Resulting Cdk2ap1(+/-:K14-Cdk2ap1) transgenic mice showed an improved incidence of full term animals (16.7% from 0.5%) on a Cdk2ap1(-/-) background. Transgenic expression of Cdk2ap1 in Cdk2ap1(-/-:K14-Cdk2ap1) animals restored SL/FW ratio to the level of Cdk2ap1(+/-:K14-Cdk2ap1) mice, but not to that of the Cdk2ap1(+/+:K14-Cdk2ap1) mice. Teratoma formation analysis using mESCs showed an abrogated in vivo pluripotency of Cdk2ap1(-/-) mESCs towards a restricted mesoderm lineage specification. This study demonstrates that Cdk2ap1 plays an essential role in the early stage of embryogenesis and has a potential role during craniofacial morphogenesis.

Cell-cycle regulation and mammalian gametogenesis: a lesson from the unexpected

The progression of mammalian gametogenesis requires a precise balance between cell-cycle activities and elimination of defective gametogenic cells to ensure the perpetuation of species. Both spermatogonia and oogonia are stem cell populations committed to meiosis with the aim of generating haploid gametes for fertilization. At puberty, mitotically dividing spermatogonial cell cohorts maintain the ability of cell renewal and occupy niches in the seminiferous tubule. In contrast, mitotically dividing oogonial cell cohorts produced in the fetal ovary, are exclusively committed to meiosis and produce primordial follicles housing a primary oocyte surrounded by somatic follicular cells. A consistent physiological event during mammalian gametogenesis is the disposal of spermatogenic cells by apoptosis and ovarian follicles by atresia. Cyclin-dependent kinases (Cdks) and their cyclin partners coordinate the activities of the cell cycle. An additional cell-cycle regulatory component is the centrosome. The centrosome harbors regulatory proteins controlling the normal progression of the cell cycle. Changes in individual centrosome proteins can lead to cell-cycle arrest and a decrease in the genomic protective function of p53 that promotes apoptosis. Disruption of cyclin A1, Cdk2, and Cdk4 expression in transgenic mice results in infertility and gonadal atrophy. Cdk-cyclin complexes interact with regulatory proteins, which may fine-tune the activities of the complex. One of the many regulatory proteins is p12, a 115 amino acid growth suppressor polypeptide designated p12(CDK2AP1), partner of Cdk2 and with binding affinity to DNA polymerase alpha/primase. Overexpression of p12 is associated with testicular and ovarian atrophy without affecting fertility. Ectopic expression of p12 was driven by the keratin 14 promoter. Keratin 14 is the pairing partner of keratin 5 and both keratins are expressed in testis. The efficiency of keratin promoters in driving ectopic gonadal gene expression, the association of gonadal atrophy with the ectopic expression of a Cdk2 regulatory protein and the centrosome, as a reservoir of cell-cycle regulatory proteins, open new experimental opportunities to address still lingering questions concerning cell differentiation and division during mammalian gametogenesis.