Comparative transcriptome and DNA methylation analysis in temperature-sensitive genic male sterile wheat BS366.

BACKGROUND: Known as the prerequisite component for the heterosis breeding system, the male sterile line determines the hybrid yield and seed purity. Therefore, a deep understanding of the mechanism and gene network that leads to male sterility is crucial. BS366, a temperature-sensitive genic male sterile (TGMS) line, is male sterile under cold conditions (12 °C with 12 h of daylight) but fertile under normal temperature (20 °C with 12 h of daylight). RESULTS: During meiosis, BS366 was defective in forming tetrads and dyads due to the abnormal cell plate. During pollen development, unusual vacuolated pollen that could not accumulate starch grains at the binucleate stage was also observed. Transcriptome analysis revealed that genes involved in the meiotic process, such as sister chromatid segregation and microtubule-based movement, were repressed, while genes involved in DNA and histone methylation were induced in BS366 under cold conditions. MethylRAD was used for reduced DNA methylation sequencing of BS366 spikes under both cold and control conditions. The differentially methylated sites (DMSs) located in the gene region were mainly involved in carbohydrate and fatty acid metabolism, lipid metabolism, and transport. Differentially expressed and methylated genes were mainly involved in cell division. CONCLUSIONS: These results indicated that the methylation of genes involved in carbon metabolism or fatty acid metabolism might contribute to male sterility in BS366 spikes, providing novel insight into the molecular mechanism of wheat male sterility.

Epididymal initial segment-specific Cre recombinase activity in Lcn8-Cre knock-in mice.

BACKGROUND: Sperm acquire the ability to fertilize ova through a complex process of epididymal maturation. To identify the functions of genes expressed in the proximal epididymis, mouse models specific to this region are needed. METHODS AND RESULTS: A Lcn8-Cre knock-in mouse line was generated using CRISPR/Cas9 technology. A 37 bp coding sequence of Lcn8 from the ATG start codon was replaced by an NLS-Cre-polyA cassette, resulting in Cre expression and the absence of Lcn8. Epididymal initial segment-specific Cre expression was identified using RT-PCR and western blotting, and the spatial-temporal Cre activity was further confirmed by using the Rosa26tdTomato reporter mice. Immunofluorescence staining showed that active Cre recombinase was present in the principal cells. Histological analyses of sperm and epididymides, and the four-month mating tests, were used to confirm that Cre expression did not affect normal development and male fecundity. CONCLUSIONS: The novel Lcn8-Cre mice can be used to establish epididymal initial segment-specific conditional knock-out mouse models.

Genome-wide identification and analysis of the COI gene family in wheat (Triticum aestivum L.).

BACKGROUND: COI (CORONATINE INSENSITIVE), an F-box component of the Skp1-Cullin-F-box protein (SCFCOI1) ubiquitin E3 ligase, plays important roles in the regulation of plant growth and development. Recent studies have shown that COIs are involved in pollen fertility. In this study, we identified and characterized COI genes in the wheat genome and analyzed expression patterns under abiotic stress. RESULTS: A total of 18 COI candidate sequences for 8 members of COI gene family were isolated in wheat (Triticum aestivum L.). Phylogenetic and structural analyses showed that these COI genes could be divided into seven distinct subfamilies. The COI genes showed high expression in stamens and glumes. The qRT-PCR results revealed that wheat COIs were involved in several abiotic stress responses and anther/glume dehiscence in the photoperiod-temperature sensitive genic male sterile (PTGMS) wheat line BS366. CONCLUSIONS: The structural characteristics and expression patterns of the COI gene family in wheat as well as the stress-responsive and differential tissue-specific expression profiles of each TaCOI gene were examined in PTGMS wheat line BS366. In addition, we examined SA- and MeJA-induced gene expression in the wheat anther and glume to investigate the role of COI in the JA signaling pathway, involved in the regulation of abnormal anther dehiscence in the PTGMS wheat line. The results of this study contribute novel and detailed information about the TaCOI gene family in wheat and could be used as a benchmark for future studies of the molecular mechanisms of PTGMS in other crops.

Transcriptome analysis of wheat seedling and spike tissues in the hybrid Jingmai 8 uncovered genes involved in heterosis.

MAIN CONCLUSION: Transcriptome analysis was carried out for wheat seedlings and spikes from hybrid Jingmai 8 and both inbred lines to unravel mechanisms underlying heterosis. Heterosis, known as one of the most successful strategies for increasing crop yield, has been widely exploited in plant breeding systems. Despite its great importance, the molecular mechanism underlying heterosis remains elusive. In the present study, RNA sequencing (RNA-seq) was performed on the seedling and spike tissues of the wheat (Triticum aestivum) hybrid Jingmai 8 (JM8) and its homozygous parents to unravel the underlying mechanisms of wheat heterosis. In total, 1686 and 2334 genes were identified as differentially expressed genes (DEGs) between the hybrid and the two inbred lines in seedling and spike tissues, respectively. Gene Ontology analysis revealed that DEGs from seedling tissues were significantly enriched in processes involved in photosynthesis and carbon fixation, and the majority of these DEGs expressed at a higher level in JM8 compared to both inbred lines. In addition, cell wall biogenesis and protein biosynthesis-related pathways were also significantly represented. These results confirmed that a combination of different pathways could contribute to heterosis. The DEGs between the hybrid and the two inbred progenitors from the spike tissues were significantly enriched in biological processes related to transcription, RNA biosynthesis and molecular function categories related to transcription factor activities. Furthermore, transcription factors such as NAC, ERF, and TIF-IIA were highly expressed in the hybrid JM8. These results may provide valuable insights into the molecular mechanisms underlying wheat heterosis.

Detection rate of prostate cancer following biopsy among the northern Han Chinese population: a single-center retrospective study of 1022 cases.

BACKGROUND: Prostate cancer is known to have ethnic and regional differences. The study aimed to clinically evaluate the detection rate of prostate cancer on transrectal ultrasonography (TRUS)-guided prostate biopsy and analyze its characteristics among the northern Han Chinese population at a single center. METHODS: Between October 2009 and September 2016, a total of 1027 Chinese men, who had undergone TRUS-guided prostate biopsy at Qingdao Municipal Hospital, were retrospectively analyzed. Prostate biopsies were performed in the case of an abnormally elevated serum PSA level, and/or abnormal digital rectal examination (DRE) findings, and/or suspicious prostatic imaging findings. RESULTS: Of the 1022 men enrolled in the analysis, 438 patients (42.8%) were diagnosed with prostate adenocarcinoma histologically. When serum PSA levels were divided into five subgroups (less than 4.0, 4.0 to 10.0, 10.0 to 20.0, 20.0 to 100.0, and ≥ 100.0 ng/ml), the detection rates of prostate cancer were 12.4, 15.9, 34.1, 66.2, and 93.8%, respectively. With serum PSA levels of 4.0 to 10.0 ng/ml, the cancer detection rates for a normal DRE and a suspect DRE finding were 13.5 and 58.2%, respectively. Accordingly, the cancer detection rates for a normal imaging and a suspect imaging finding were 13.5 and 58.2%, respectively. Besides, a large proportion of the patients were in the clinically advanced stage. CONCLUSIONS: The present study data reported a relatively higher prostate cancer detection rate of 42.8% and that the majority of the patients presented with clinically advanced prostate cancers within a local clinical urologic practice. An early detection and screening program for prostate cancer is of great need to reduce the burden from this disease among the northern Han Chinese population.

Decreased expression of elastin and lysyl oxidase family genes in urogenital tissues of aging mice.

AIM: This study aims to investigate the expression levels of elastin and lysyl oxidase (LOX) family members in the urogenital tissues of natural aging mice and accelerated ovarian aging mice. METHOD: Uteri, vaginas and bladders were harvested from 18-month-old female mice and accelerated ovarian aging mice developed by chemotherapeutic agents. Untreated 3-month-old female mice were used as controls. The expression levels of elastin and LOX family members were determined by real-time polymerase chain reaction and western blot. RESULTS: Compared with untreated young female mice, the expression of elastin and LOX family members significantly decreased both in natural aging mice and accelerated ovarian aging mice. CONCLUSION: Aging is a high-risk factor for pelvic floor disorders. The failure of elastic fiber synthesis and assembly due to the decline in expression levels of elastin and LOX family members during aging may explain the molecular mechanism causing pelvic floor disorders.

[Risk factors of prostate cancer in urban Qingdao: a case-control study].

OBJECTIVE: To investigate the risk factors of prostate cancer in urban Qingdao and provide some theoretical evidence for the scientific prevention and treatment of the disease. METHODS: We performed a hospital-based matched case-control study in Qingdao Municipal Hospital. The cases and controls were matched in age, gender, nationality and the place of residence. All the subjects were interviewed face to face in the hospital using a questionnaire, and the data analyzed by the conditional logistic regression method. RESULTS: According to the 258 valid questionnaires collected, the prostate cancer risk was significantly higher in the cases with a family history of cancer than in those without (OR = 2.58), and so was it in the men with the first spermatorrhea at the age of < or = 15 years than in those at the age of > or = 18 years (OR = 2.27). A decreased risk of prostate cancer was found among the men with the first experience of sexual intercourse between 25 to 30 years of age (OR = 0.76). An increased risk was shown in those with sexual intercourses > or = 4 times per week before 35 years old (OR = 2.57), masturbations > or = 3 times per week (OR = 2.30) and a drinking history (alcohol > or = 150 g/d) of > or = 10 years (OR = 2.83). CONCLUSION: Positive family history of cancer, earlier age of the first spermatorrhea, sexual intercourses > or = 4 times per week before 35 years old, frequent masturbations, and heavy drinking for more than 10 years are risk factors for prostate cancer.

[Tea polyphenols inhibits the proliferation of prostate cancer DU145 cells].

OBJECTIVE: To investigate the effect of tea polyphenols on the proliferation of human prostate cancer cells and its possible mechanism. METHODS: We cultured androgen-independent prostate cancer DU145 cells in the medium with different concentrations (50, 100, 250 and 500 microg/ml) of tea polyphenols, and those in the normal medium as the control. After 48 hours of culture, we detected the survival rate of the cells by MTT assay and determined the expression of survivin by Western blot and quantitative RT-PCR. RESULTS: At 48 hours, the survival rates of the prostate cancer DU145 cells were 0.97 +/- 0.12, 0.71 +/- 0.07, 0.20 +/- 0.03 and 0.08 +/- 0.01 in the 50, 100, 250 and 500 microg/ml tea polyphenols treatment groups, all significantly reduced as compared with the control group (P < 0.01) except that of the 50 microg/ml group (P = 0.42). Furthermore, the survival rate continued to decrease with the prolonging of time, dropping below 5% at 96 hours except in the 50 microg/ml group. The grey values of the survivin expression in the 100, 250 and 500 microg/ml tea polyphenols groups were 13 425 +/- 34, 2 017 +/- 24 and 1 274 +/- 22, respectively, at 48 hours, significantly lower than 15 075 +/- 48 in the control group (P < 0.01). Moreover, the content of survivin mRNA at 48 hours was markedly lower in the 50, 100, 250 and 500 microg/ml treatment groups (0.74 +/- 0.03, 0.64 +/- 0.02, 0.52 +/- 0.01 and 0.21 +/- 0.02) than in the control (P < 0.01). CONCLUSION: Tea polyphenols can inhibit the proliferation of human prostate cancer DU145 cells, which may be associated with the decreased expression of the survivin gene.

The efficacy and safety of alpha-adrenergic blockers for medical expulsion therapy in patients with ureteral calculi: A meta-analysis of placebo-controlled trials.

PURPOSE: Alpha-adrenergic blockers are commonly used as a medical expulsive therapy (MET) for patients with ureteral calculi. The aim of this meta-analysis was to evaluate the efficacy and safety of alpha-adrenergic blockers compared with a placebo when used as a MET. MATERIALS AND METHODS: We carried out a systematic search of the PubMed, EMBASE, and Web of Science databases, and the Cochrane Library, for relevant articles from inception to November 2020. Our aim was to identify placebo-controlled trails in which patients were randomized to receive either alpha-adrenergic blockers (tamsulosin, alfuzosin, doxazosin, terazosin, naftopidil, or silodosin) or a placebo for the treatment of ureteral calculi. RESULTS: According to strict inclusion criteria, database searches identified 8 placebo-controlled studies that included 2284 patients. Generally, α-blockers had no significant effect on the clearance of stones in the urinary tract (risk ratio [RR] = 1.05; 95% confidence interval [CI] = 1.00-1.11). However, subgroup analysis showed that α-blockers were effective in treating distal urinary tract stones (RR = 1.08; 95% CI = 1.02-1.15). With regards to adverse events, our analysis showed that the combination of MET with α-blockers was likely to cause dizziness (RR = 1.37; 95% CI = 1.06-1.79) and retrograde ejaculation (RR = 3.10; 95% CI = 1.81-5.29). CONCLUSION: Although α-blockers cannot improve the overall ureteral stone clearance rate, these drugs are still effective for the treatment of stones in the distal urinary tract. However, the application of α-blockers is likely to cause dizziness and/or retrograde ejaculation.

A novel mouse line with epididymal initial segment-specific expression of Cre recombinase driven by the endogenous Lcn9 promoter.

Spermatozoa released from testes undergo a maturation process and acquire the capacity to fertilize ova through epididymal transit. The epididymis is divided into four regions, each with unique morphology, gene profile, luminal microenvironment and distinct function. To study the functions of relevant genes in the epididymal initial segment (IS), a novel IS-specific mouse model, Lcn9-Cre knock-in (KI) mouse line was generated via CRISPR/Cas9 technology. The TAG stop codon was replaced by a 2A-NLS-Cre cassette, resulting in the co-expression of Lcn9 and Cre recombinase. IS-specific Cre expression was first observed from postnatal day 17. Using the Rosa26tdTomato reporter mice, the Cre-mediated DNA recombination was detected exclusively in principal cells. The epididymal IS-specific Cre activity in vivo was further confirmed using Lcn9-Cre mice crossed with a mouse strain carrying Tsc1 floxed alleles (Tsc1flox/+). Cre expression did not affect either normal development or male fecundity. Different from any epididymis-specific Cre mice reported previously, the novel Lcn9-Cre mouse line can be used to introduce entire IS-specific conditional gene editing for gene functional study.

[CuZn-SOD and MDA in the serum and EPS of chronic prostatitis patients: quantitative determination and analysis].

OBJECTIVE: Chronic prostatitis (CP) is a common disease in adult males. Oxidative stress injury has been found to play a significant role in the pathogenesis of CP in recent studies. This study aimed to determine the contents of CuZn-super oxide dismutase (CuZn-SOD) and malondialdehyde (MDA) in the serum and EPS in CP patients and healthy men, and investigate their significance in the diagnosis and treatment of the CP. METHODS: A total of 120 out-patients with confirmed CP were equally divided into a type II, a type IIIA and a type IIIB group, and another 40 healthy males were included as controls. We determined the contents of CuZn-SOD and MDA in the serum and EPS of each group and compared their differences. RESULTS: No significant differences were found in the serum CuZn-SOD content among the four groups (P > 0.05). The MDA contents were markedly higher in the CP groups than in the control (P < 0.01), but with no significant differences among the three CP groups (P > 0.05). The CuZn-SOD contents in EPS were remarkably lower in the type II and type III A than in the type III B and control groups (P < 0.01), but with no significant differences between the type II and type III A as well as between the type III B and control groups (P > 0.05). The MDA contents in EPS were markedly higher in the type II and type III A than in the type III B and control groups (P < 0.01), but with no significant differences between the type II and type III A as well as the type III B and control groups (P > 0.05). CONCLUSION: Oxidative stress is stronger in type II and type III A CP patients than in healthy men, but has no significant difference between type III B patients and non-CP males. Determining the contents of CuZn-SOD and MDA in the serum and EPS could be very valuable for the diagnosis and assessment of chronic prostatitis.

[The significance of Ki-67 antigen expression in the distinction between benign and malignant pheochromocytomas].

OBJECTIVES: To investigate the expression of Ki-67 antigen in benign and malignant pheochromocytomas, and to evaluate whether the expression of Ki-67 antigen could serve as a diagnostic marker for predicting the biological behaviour of these tumors. METHODS: Ki-67 antigen were detected by immunohistochemical technique and image analysis in 57 cases of clinically documented benign and malignant pheochromocytomas were analyzed. Aside from histological study, Ki-67 immunohistochemistry studies were performed to get the Ki-67 index. Statistical analysis was performed between these groups. RESULTS: Ki-67 index was low in benign pheochromocytomas (average 0.98%), and high in malignant pheochromocytomas (average 3.78%). There was statistically significant difference in expressions of Ki-67 antigen between benign and malignant pheochromocytomas. The Ki-67 index of 2 cases in benign pheochromocytomas (5.1%, 2/39) and 10 cases in malignant pheochromocytomas (55.6%, 10/18) was higher than 3%. The accuracy, sensitivity, specificity, positive predictive value and negative predictive value of Ki-67 index higher than 3% to diagnosis malignant pheochromocytomas was 82.5%, 55.6%, 94.9%, 83.3% and 82.2%. The follow-ups indicated the survival rate of patients with higher Ki-67 index was lower than those with lower Ki-67 index. CONCLUSIONS: Ki-67 may serve as a useful marker of the biological behavior of tumors, and can provide useful information for prognosis of tumor patients. Immunohistochemical assessment of Ki-67 antigen can be useful in the differential diagnosis of malignant from benign pheochromocytomas. Ki-67 index (> 3%) is a useful marker for distinguishing benign from malignant tumors or for predicting the malignant potential of pheochromocytomas.

Rcan2 and estradiol independently regulate body weight in female mice.

Rcan2 increases food intake and plays an important role in the development of age- and diet- induced obesity in male mice. However, in females, wild-type mice grow almost at a similar rate as Rcan2-/- mice on normal chow diet from 6 weeks of age. Here we showed that the ability of Rcan2 to promote weight gain was attenuated by energy expenditure mediated by 17ß-estradiol in female mice. Using ovariectomy-operated models, we found that 17ß-estradiol deprivation did not alter food intake, but induced more weight gain in wild-type mice than Rcan2-/- mice. If wild-type mice ingested equally as Rcan2-/- mice, in the same ovarian state they exhibited similar weight changes, but the mice in ovariectomized groups were significantly heavier than the ovarian-intact mice, suggesting that body weight is not only regulated by Rcan2, but also by 17ß-estradiol. Furthermore, we demonstrated that Rcan2 and 17ß-estradiol independently regulated body weight even on high-fat diets. Therefore, our findings indicate that Rcan2 and 17ß-estradiol regulate body weight through different mechanisms. Rcan2 increases food intake, whereas 17ß-estradiol promotes energy expenditure. These findings provide novel insights into the sexual dimorphism of body weight regulation.

Downregulation of fatty acid synthase complex suppresses cell migration by targeting phosphor-AKT in bladder cancer.

The aim of the present study was to investigate the effect of fatty acid synthase complex (FASN) on the migration capacity of bladder transitional cell carcinoma (BTCC) cells and the involvement of matrix metalloproteinase­9 (MMP­9) via targeting of phospho­AKT (p­AKT). FASN­specific small­interfering RNA (FASN­siRNA) was used to inhibit FASN gene expression in the 5637 and 253J BTCC cell lines. The knockdown efficiency of FAM­conjugated FASN­siRNA was confirmed by fluorescence microscopy. The migratory abilities of BTCC cells were assessed using a Transwell assay. Furthermore, protein and mRNA expression of FASN, p­AKT, AKT, and migration­associated protein MMP­9 were detected by western blot analysis. Treatment with FASN inhibitor Cer and FASN­siRNA decreased the migratory capacity of bladder cancer cells and reduced the levels of p­AKT as well as the expression of MMP­9. These results indicated that FASN inhibition suppressed the migratory capacity of BTCC cells through suppressing AKT activation and consequently reducing MMP­9 expression. Targeting FASN may represent a promising novel therapeutic strategy for BTCC.

A disputed evidence on obesity: comparison of the effects of Rcan2(-/-) and Rps6kb1(-/-) mutations on growth and body weight in C57BL/6J mice.

It is widely accepted that body weight and adipose mass are tightly regulated by homeostatic mechanisms, in which leptin plays a critical role through hypothalamic pathways, and obesity is a result of homeostatic disorder. However, in C57BL/6J mice, we found that Rcan2 increases food intake and plays an important role in the development of age- and diet-induced obesity through a leptin-independent mechanism. RCAN2 was initially identified as a thyroid hormone (T3)-responsive gene in human fibroblasts. Expression of RCAN2 is regulated by T3 through the PI3K-Akt/PKB-mTOR-Rps6kb1 signaling pathway. Intriguingly, both Rcan2(-/-) and Rps6kb1(-/-) mutations were reported to result in lean phenotypes in mice. In this study we compared the effects of these two mutations on growth and body weight in C57BL/6J mice. We observed reduced body weight and lower fat mass in both Rcan2(-/-) and Rps6kb1(-/-) mice compared to the wild-type mice, and we reported other differences unique to either the Rcan2(-/-) or Rps6kb1(-/-) mice. Firstly, loss of Rcan2 does not directly alter body length; however, Rcan2(-/-) mice exhibit reduced food intake. In contrast, Rps6kb1(-/-) mice exhibit abnormal embryonic development, which leads to smaller body size and reduced food intake in adulthood. Secondly, when fed a normal chow diet, Rcan2(-/-) mice weigh significantly more than Rps6kb1(-/-) mice, but both Rcan2(-/-) and Rps6kb1(-/-) mice develop similar amounts of epididymal fat. On a high-fat diet, Rcan2(-/-) mice gain body weight and fat mass at slower rates than Rps6kb1(-/-) mice. Finally, using the double-knockout mice (Rcan2(-/-) Rps6kb1(-/-)), we demonstrate that concurrent loss of Rcan2 and Rps6kb1 has an additive effect on body weight reduction in C57BL/6J mice. Our data suggest that Rcan2 and Rps6kb1 mutations both affect growth and body weight of mice, though likely through different mechanisms.

Estradiol plays a role in regulating the expression of lysyl oxidase family genes in mouse urogenital tissues and human Ishikawa cells.

The lysyl oxidase (LOX) family encodes the copper-dependent amine oxidases that play a key role in determining the tensile strength and structural integrity of connective tissues by catalyzing the crosslinking of elastin or collagen. Estrogen may upregulate the expression of LOX and lysyl oxidase-like 1 (LOXL1) in the vagina. The objective of this study was to determine the effect of estrogen on the expression of all LOX family genes in the urogenital tissues of accelerated ovarian aging mice and human Ishikawa cells. Mice and Ishikawa cells treated with estradiol (E2) showed increased expression of LOX family genes and transforming growth factor ß1 (TGF-ß1). Ishikawa cells treated with TGF-ß1 also showed increased expression of LOX family genes. The Ishikawa cells were then treated with either E2 plus the TGF-ß receptor (TGFBR) inhibitor SB431542 or E2 alone. The expression of LOX family genes induced by E2 was reduced in the Ishikawa cells treated with TGFBR inhibitor. Our results showed that E2 increased the expression of the LOX family genes, and suggest that this induction may be mediated by the TGF-ß signal pathway. E2 may play a role in regulating the expression of LOX family genes.

Accelerated ovarian aging in mice by treatment of busulfan and cyclophosphamide.

Busulfan/cyclophosphamide (Bu/Cy) conditioning regimen has been widely used to treat cancer patients, while their effects on major internal organs in females are not fully understood. We treated female mice with Bu/Cy, and examined the histopathology of major internal organs on Day 30 after the treatment. The results show that Bu/Cy treatment affected the ovaries most extensively, while it had less effect on the spleen, lungs, and kidneys, and no effect on the heart, liver, stomach, and pancreas. To better understand the effect of Bu/Cy on the ovaries, we counted follicles, and determined the levels of ovarian steroids. The Bu/Cy-treated mice showed a reduction of primordial and primary follicles (P<0.01) on Day 30 and a marked loss of follicles at all developmental stages (P<0.01) on Day 60. Plasma levels of estradiol and progesterone in Bu/Cy-treated mice decreased by 43.9% and 61.4%, respectively. Thus, there was a gradual process of follicle loss and low estradiol in Bu/Cy-treated mice; this is a profile similar to what is found in women with premature ovarian failure (POF). The Bu/Cy-treated mice may serve as a useful animal model to study the dynamics of follicle loss in women undergoing POF.

Induced pluripotent stem cells: origins, applications, and future perspectives.

Embryonic stem (ES) cells are widely used for different purposes, including gene targeting, cell therapy, tissue repair, organ regeneration, and so on. However, studies and applications of ES cells are hindered by ethical issues regarding cell sources. To circumvent ethical disputes, great efforts have been taken to generate ES cell-like cells, which are not derived from the inner cell mass of blastocyst-stage embryos. In 2006, Yamanaka et al. first reprogrammed mouse embryonic fibroblasts into ES cell-like cells called induced pluripotent stem (iPS) cells. About one year later, Yamanaka et al. and Thomson et al. independently reprogrammed human somatic cells into iPS cells. Since the first generation of iPS cells, they have now been derived from quite a few different kinds of cell types. In particular, the use of peripheral blood facilitates research on iPS cells because of safety, easy availability, and plenty of cell sources. Now iPS cells have been used for cell therapy, disease modeling, and drug discovery. In this review, we describe the generations, applications, potential issues, and future perspectives of iPS cells.

Conditional gene manipulation: Cre-ating a new biological era.

To solve the problem of embryonic lethality in conventional gene knockouts, site-specific recombinase (SSR) systems (Cre-loxP, Flp-FRT, and ΦC31) have been used for tissue-specific gene knockout. With the combination of an SSR system and inducible gene expression systems (tetracycline and tamoxifen), stage-specific knockout and transgenic expression can be achieved. The application of this "SSR+inducible" conditional tool to genomic manipulation can be extended in various ways. Alternatives to conditional gene targeting, such as conditional gene trapping, multipurpose conditional alleles, and conditional gene silencing, have been developed. SSR systems can also be used to construct precise disease models with point mutations and chromosomal abnormalities. With these exciting achievements, we are moving towards a new era in which the whole genome can be manipulated as we wish.