对与小鼠胚胎发育相关的印记基因Mcts2的研究

目的：对与小鼠胚胎发育相关的印记基因Mcts2表达模式及生物学功能做初步的分析。方法：采用切片原位杂交,全胚胎原位杂交,Northern blot和real-time PCR对该基因进行了表达谱的分析。结果：切片原位杂交结果显示Mcts2基因在E13.5和E15.5胚胎中的脑、舌、心脏、肺脏、肝脏、肾脏等重要脏器中都有普遍表达。全胚胎原位杂交结果显示Mcts2基因在E10.5胚胎中的前脑、前肢、尾芽中出现较强的信号,其他部位信号较弱。Northern和Real-time PCR实验分析了Mcts2基因在E12.5,E15.5,E18.5胚胎和新生小鼠的脑、心脏、肺脏、肝脏和肾脏中的表达谱,发现Mcts2基因在这几个主要发育时期都有普遍表达,在E15.5胚胎中表达信号最为强烈。结论：Mcts2基因在小鼠胚胎的发育的各主要时期的重要脏器中都有普遍的表达,提示该基因在小鼠胚胎发育过程中起到了重要的作用。     

Lysine 92 amino acid residue of USP46, a gene associated with 'behavioral despair' in mice, influences the deubiquitinating enzyme activity

Deubiquitinating enzymes (DUBs) regulate diverse cellular functions by their activity of cleaving ubiquitin from specific protein substrates. Ubiquitin-Specific Protease 46 (USP46) has recently been identified as a quantitative trait gene responsible for immobility in the tail suspension test and forced swimming test in mice. Mice with a lysine codon (Lys 92) deletion in USP46 exhibited loss of 'behavioral despair' under inescapable stresses in addition to abnormalities in circadian behavioral rhythms and the GABAergic system. However, whether this deletion affects enzyme activity is unknown. Here we show that USP46 has deubiquitinating enzyme activity detected by USP cleavage assay using GST-Ub52 as a model substrate. Interestingly, compared to wild type, the Lys 92 deletion mutant resulted in a decreased deubiquitinating enzyme activity of 27.04%. We also determined the relative expression levels of Usp46 in rat tissues using real-time RT-PCR. Usp46 mRNA was expressed in various tissues examined including brain, with the highest expression in spleen. In addition, like rat USP46, both human and mouse USP46 are active toward to the model substrate, indicating the USP cleavage assay is a simple method for testing the deubiquitinating enzyme activity of USP46. These results suggest that the Lys 92 deletion of USP46 could influence enzyme activity and thereby provide a molecular clue how the enzyme regulating the pathogenesis of mental illnesses.     

Isolation and characterization of the mouse ubiquitin-specific protease Usp15

We have characterized the mouse ortholog of the human ubiquitin-specific protease USP15. Mouse Usp15 consists of 981 amino acids with a predicted molecular mass of 112 kDa, contains the highly conserved Cys and His boxes present in all members of the UBP family of deubiquitinating enzymes, and is 98% identical/99% similar to human USP15. Usp15 shares 59.5% identity/75.5% sequence similarity with the mouse Unp(Usp4) oncoprotein. Recombinant Usp15 demonstrated ubiquitin-specific protease activity against engineered linear fusions of ubiquitin to glutathione S-transferase. Usp15 can also cleave the ubiquitin-proline bond, as can USP15 and Usp4. Alignment of mouse and human Usp15 and Usp4 protein sequences suggested that Usp15/USP15 may be alternately spliced in a manner analogous to Usp4. Sequence analysis of RT-PCR products from several human and mouse cell lines and tissues revealed alternate splicing in all cells studied. Northern blot analysis of both mouse and human Usp15 revealed two differently sized mRNAs in all tissues examined, owing to alternate polyadenylation sites spaced by 1.5 kb. Chromosomal mapping by interspecific backcross analysis localized the Usp15 gene to the distal region of mouse Chromosome (Chr) 10. This region is syntenic with human Chr 12q24, the location of human USP15, and a different location to Unp(Usp4) (Chr 9). Identification of the mouse Usp15 gene (>69.5 kb) and human USP15 gene (145 kb) sequences in genome databases reveals that both are composed of 22 exons with identical splice sites, and both have an exon/intron structure identical to the mouse Usp4 gene, including the alternately spliced exon. Phylogenetic studies suggest that a sequence currently identified as a chicken Usp4 ortholog is in fact a USP15 ortholog, while bona-fide chicken, cow, and rat Usp4 orthologs can be identified in EST databases.     

A novel role for the deubiquitinase USP1 in the control of centrosome duplication

Defects in the regulation of centrosome duplication lead to tumorigenesis through abnormal cell division and resulting chromosome missegregation. Therefore, maintenance of accurate centrosome number is critical for cell fate. The deubiquitinating enzyme USP1 plays important roles in DNA repair and cell differentiation. Importantly, increased levels of USP1 are detected in certain types of human cancer, but little is known about the significance of USP1 overexpression in cancer development. Here we show that Usp1 plays a novel role in regulating centrosome duplication. The ectopic expression of wild-type Usp1, but not C90S Usp1 (catalytically inactive mutant form), induced centrosome amplification. Conversely, ablation of Usp1 in mouse embryonic fibroblasts (MEFs) showed a significant delay in centrosome duplication. Moreover, Usp1-induced centrosome amplification caused abnormal mitotic spindles, chromosome missegregation and aneuploidy. Interestingly, loss of inhibitor of DNA binding protein 1 (ID1) suppressed Usp1-induced centrosome amplification. Taken together, our results strongly suggest that Usp1 is involved in the regulation of centrosome duplication, at least in part via ID1, and Usp1 may exert its oncogenic activity, partially through inducing centrosome abnormality.     

Mice lacking the USP2 deubiquitinating enzyme have severe male subfertility associated with defects in fertilization and sperm motility

The ubiquitin-proteasome system plays an important role in spermatogenesis. However, the functions of deubiquitinating enzymes in this process remain poorly characterized. We previously showed that the deubiquitinating enzyme USP2 is induced in late elongating spermatids. To identify its function, we generated mice lacking USP2. Usp2 -/- mice appeared normal, and the weights of major organs, including the testis, did not differ from wild type (Usp2 +/+). However, although the numbers of testicular spermatids and epididymal spermatozoa were normal in Usp2 -/- males, these animals had a severe defect in fertility, yielding only 12% as many offspring as Usp2 +/+ littermates. Spermatogenesis in Usp2 -/- mice was morphologically normal except for the presence of abnormal aggregations of elongating spermatids and formation of multinucleated cells in some tubules. The epididymal epithelium was morphologically normal in Usp2 -/- mice, but some abnormal cells other than sperm were present in the lumen. Usp2 -/- epididymal spermatozoa manifested normal motility when incubated in culture media, but rapidly became immotile when incubated in PBS in contrast to Usp2 +/+ spermatozoa, which largely maintained motility under this condition. Usp2 -/- and +/+ spermatozoa underwent acrosome reactions in vitro with similar frequency. In vitro fertilization assays demonstrated a severe defect in the ability of Usp2 -/- spermatozoa to fertilize eggs. This could be bypassed by intracytoplasmic sperm injection or removal of the zona pellucida, which resulted in fertilization rates similar to that of Usp2 +/+ mice. We demonstrate for the first time, using mouse transgenic approaches, a role for the ubiquitin system in fertilization.     

USP4 inhibits p53 through deubiquitinating and stabilizing ARF-BP1

Tumour suppressor p53 levels in the cell are tightly regulated by controlled degradation through ubiquitin ligases including Mdm2, COP1, Pirh2, and ARF-BP1. The ubiquitination process is reversible via deubiquitinating enzymes, such as ubiquitin-specific peptidases (USPs). In this study, we identified ubiquitin-specific peptidase 4 (USP4) as an important regulator of p53. USP4 interacts directly with and deubiquitinates ARF-BP1, leading to the stabilization of ARF-BP1 and subsequent reduction of p53 levels. Usp4 knockout mice are viable and developmentally normal, but showed enhanced apoptosis in thymus and spleen in response to ionizing radiation. Compared with wild-type mouse embryonic fibroblasts (MEFs), Usp4-/- MEFs exhibited retarded growth, premature cellular senescence, resistance to oncogenic transformation, and hyperactive DNA damage checkpoints, consistent with upregulated levels and activity of p53 in the absence of USP4. Finally, we showed that USP4 is overexpressed in several types of human cancer, suggesting that USP4 is a potential oncogene.     

Grb10基因在小鼠胚期特异性表达分析

生长因子受体结合蛋白10(Growth factor receptor-bound protein 10, Grb10)是一个存在于小鼠11号染色体和人7号染色体的母本表达的印记基因。文章利用原位杂交技术和定量RT-PCR方法对不同发育阶段的小鼠胚胎Grb10 基因进行时空表达谱的分析, 以确定该基因在胚胎发育中其表达与组织发育的关系。定量RT-PCR数据结果表明, Grb10在E8.5-E13.5 (Embryonic days 8.5-13.5), 表达水平逐渐增高, 在E13.5达到高峰, 后期表达量回落。在胚胎发育的中后期脑、心、肺组织的表达水平呈递减趋势。肝脏组织中Grb10表达水平较为恒定, 在E18.5出现高峰。原位杂交数据验证了定量RT-PCR的结果, 并且说明了Grb10在其他如骨、肾和肌肉等组织器官的高表达水平。研究结果表明Grb10基因是小鼠胚期发育的一个重要的基因。     

Conserved expression of the PRELI domain containing 2 gene (<Emphasis Type="Italic">Prelid2</Emphasis>) during mid-later-gestation mouse embryogenesis

Prelid2, which belongs to the PRELI domain containing family, is identified as a conserved evolution gene. The expression and regulation during embryonic development of the prelid2 gene is unknown. In this study, we investigated the prelid2 gene expression and regulation using mouse embryos model, by in situ hybridization analysis, RT-PCR and bisulfite sequencing. In situ hybridization analysis showed that prelid2 gene expression were found in midbrain, spinal cord, optic eminence, otic vesicle and tail at E9.5 and E10.5 embryos, in forebrain, hindbrain, heart, lung, liver and kidney at E13.5 and E15.5 embryos. Real-time quantitative RT-PCR results verified the expression pattern in the four major mouse organs, brain, heart, lung, and liver during organs differentiation and formation. Bisulfite sequencing illustrated the consistent result of expression and its unmethylation status in the genomic promoter region at E12.5, E18.5, and new born. Thus, the prelid2 gene is a widely-spread, persistently expressed and unmethylated gene in mouse embryonic development. Our results suggest that the PRELI domain containing 2 gene is involved in mouse embryonic development.     

In situ hybridization analysis of the temporospatial expression of the midkine/pleiotrophin family in rat embryonic pituitary gland

Pituitary gland development is controlled by numerous signaling molecules, which are produced in the oral ectoderm and diencephalon. A newly described family of heparin-binding growth factors, namely midkine (MK)/pleiotrophin (PTN), is involved in regulating the growth and differentiation of many tissues and organs. Using in situ hybridization with digoxigenin-labeled cRNA probes, we detected cells expressing MK and PTN in the developing rat pituitary gland. At embryonic day 12.5 (E12.5), MK expression was localized in Rathke’s pouch (derived from the oral ectoderm) and in the neurohypophyseal bud (derived from the diencephalon). From E12.5 to E19.5, MK mRNA was expressed in the developing neurohypophysis, and expression gradually decreased in the developing adenohypophysis. To characterize MK-expressing cells, we performed double-staining of MK mRNA and anterior pituitary hormones. At E19.5, no MK-expressing cells were stained with any hormone. In contrast, PTN was expressed only in the neurohypophysis primordium during all embryonic stages. In situ hybridization clearly showed that MK was expressed in primitive (immature/undifferentiated) adenohypophyseal cells and neurohypophyseal cells, whereas PTN was expressed only in neurohypophyseal cells. Thus, MK and PTN might play roles as signaling molecules during pituitary development.