Tysnd1 deficiency in mice interferes with the peroxisomal localization of PTS2 enzymes, causing lipid metabolic abnormalities and male infertility.

Peroxisomes are subcellular organelles involved in lipid metabolic processes, including those of very-long-chain fatty acids and branched-chain fatty acids, among others. Peroxisome matrix proteins are synthesized in the cytoplasm. Targeting signals (PTS or peroxisomal targeting signal) at the C-terminus (PTS1) or N-terminus (PTS2) of peroxisomal matrix proteins mediate their import into the organelle. In the case of PTS2-containing proteins, the PTS2 signal is cleaved from the protein when transported into peroxisomes. The functional mechanism of PTS2 processing, however, is poorly understood. Previously we identified Tysnd1 (Trypsin domain containing 1) and biochemically characterized it as a peroxisomal cysteine endopeptidase that directly processes PTS2-containing prethiolase Acaa1 and PTS1-containing Acox1, Hsd17b4, and ScpX. The latter three enzymes are crucial components of the very-long-chain fatty acids ß-oxidation pathway. To clarify the in vivo functions and physiological role of Tysnd1, we analyzed the phenotype of Tysnd1(-/-) mice. Male Tysnd1(-/-) mice are infertile, and the epididymal sperms lack the acrosomal cap. These phenotypic features are most likely the result of changes in the molecular species composition of choline and ethanolamine plasmalogens. Tysnd1(-/-) mice also developed liver dysfunctions when the phytanic acid precursor phytol was orally administered. Phyh and Agps are known PTS2-containing proteins, but were identified as novel Tysnd1 substrates. Loss of Tysnd1 interferes with the peroxisomal localization of Acaa1, Phyh, and Agps, which might cause the mild Zellweger syndrome spectrum-resembling phenotypes. Our data established that peroxisomal processing protease Tysnd1 is necessary to mediate the physiological functions of PTS2-containing substrates.

Conditional expression of constitutively active estrogen receptor α in chondrocytes impairs longitudinal bone growth in mice.

Estrogen plays important roles in the regulation of chondrocyte proliferation and differentiation, which are essential steps for longitudinal bone growth; however, the mechanisms of estrogen action on chondrocytes have not been fully elucidated. In the present study, we generated conditional transgenic mice, designated as caERα(ColII), expressing constitutively active mutant estrogen receptor (ER) α in chondrocytes, using the chondrocyte-specific type II collagen promoter-driven Cre transgenic mice. caERα(ColII) mice showed retardation in longitudinal growth, with short bone lengths. BrdU labeling showed reduced proliferation of hypertrophic chondrocytes in the proliferating layer of the growth plate of tibia in caERα(ColII) mice. In situ hybridization analysis of type X collagen revealed that the maturation of hypertrophic chondrocytes was impaired in caERα(ColII) mice. These results suggest that ERα is a critical regulator of chondrocyte proliferation and maturation during skeletal development, mediating longitudinal bone growth in vivo.

Conditional expression of human bone Gla protein in osteoblasts causes skeletal abnormality in mice.

Bone Gla protein (BGP), also known as osteocalcin, is one of the most abundant γ-carboxylated noncollagenous protein in bone matrix and plays important roles in mineralization and calcium ion homeostasis. BGP is synthesized specifically in osteoblasts; however, its precise function in bone metabolism has not been fully elucidated. To investigate the in vivo function of human BGP (hBGP), we generated CAG-GFP(floxed)-hBGP transgenic mice carrying a transgene cassette composed of the promoter and a floxed GFP linked to hBGP cDNA. The mice were crossed with ColI-Cre mice, which express the Cre recombinase driven by the mouse collagen type 1a1 gene promoter, to obtain hBGP(ColI) conditional transgenic mice that expressed human BGP in osteoblasts. The hBGP(ColI) mice did not survive more than 2days after birth. The analysis of the 18.5-day post coitum fetuses of the hBGP(ColI) mice revealed that they displayed abnormal skeletal growth such as deformity of the rib and short femur and cranium lengths. Moreover, increased BGP levels were detected in the serum of the neonates. These findings indicate that hBGP expression in osteoblasts resulted in the abnormal skeletal growth in the mice. Our study provides a valuable model for understanding the fundamental role of BGP in vivo.

Mechanisms of the hepatoprotective effects of tamoxifen against drug-induced and chemical-induced acute liver injuries.

Although estrogen receptor (ER)α agonists, such as estradiol and ethinylestradiol (EE2), cause cholestasis in mice, they also reduce the degree of liver injury caused by hepatotoxicants as well as ischemia-reperfusion. The functional mechanisms of ERα have yet to be elucidated in drug-induced or chemical-induced liver injury. The present study investigated the effects of an ERα agonist, selective ER modulators (SERMs) and an ER antagonist on drug-induced and chemical-induced liver injuries caused by acetaminophen, bromobenzene, diclofenac, and thioacetamide (TA). We observed hepatoprotective effects of EE2, tamoxifen (TAM) and raloxifene pretreatment in female mice that were exposed to a variety of hepatotoxic compounds. In contrast, the ER antagonist did not show any hepatoprotective effects. DNA microarray analyses suggested that monocyte to macrophage differentiation-associated 2 (Mmd2) protein, which has an unknown function, is commonly increased by TAM and RAL pretreatment, but not by pretreatment with the ER antagonist. In ERα-knockout mice, the hepatoprotective effects of TAM and the increased expression of Mmd2 mRNA were not observed in TA-induced liver injury. To investigate the function of Mmd2, the expression level of Mmd2 mRNA was significantly knocked down to approximately 30% in mice by injection of siRNA for Mmd2 (siMmd2). Mmd2 knockdown resulted in a reduction of the protective effects of TAM on TA-induced liver injury in mice. This is the first report of the involvement of ERα in drug-induced or chemical-induced liver injury. Upregulation of Mmd2 protein in the liver was suggested as the mechanism of the hepatoprotective effects of EE2 and SERMs.

Dual roles of smad proteins in the conversion from myoblasts to osteoblastic cells by bone morphogenetic proteins.

Bone morphogenetic proteins (BMPs) induce ectopic bone formation in muscle tissue in vivo and convert myoblasts such that they differentiate into osteoblastic cells in vitro. We report here that constitutively active Smad1 induced osteoblastic differentiation of C2C12 myoblasts in cooperation with Smad4 or Runx2. In floxed Smad4 mice-derived cells, Smad4 ablation partially suppressed BMP-4-induced osteoblast differentiation. In contrast, the BMP-4-induced inhibition of myogenesis was lost by Smad4 ablation and restored by Smad4 overexpression. A nuclear zinc finger protein, E4F1, was identified as a possible component of the Smad4 complex that suppresses myogenic differentiation in response to BMP signaling. In the presence of Smad4, E4F1 stimulated the expression of Ids. Taken together, these findings suggest that the Smad signaling pathway may play a dual role in the BMP-induced conversion of myoblasts to osteoblastic cells.

Transcriptional coactivator PC4 stimulates promoter escape and facilitates transcriptional synergy by GAL4-VP16.

Positive cofactor 4 (PC4) is a coactivator that strongly augments transcription by various activators, presumably by facilitating the assembly of the preinitiation complex (PIC). However, our previous observation of stimulation of promoter escape in GAL4-VP16-dependent transcription in the presence of PC4 suggested a possible role for PC4 in this step. Here, we performed quantitative analyses of the stimulatory effects of PC4 on initiation, promoter escape, and elongation in GAL4-VP16-dependent transcription and found that PC4 possesses the ability to stimulate promoter escape in response to GAL4-VP16 in addition to its previously demonstrated effect on PIC assembly. This stimulatory effect of PC4 on promoter escape required TFIIA and the TATA box binding protein-associated factor subunits of TFIID. Furthermore, PC4 displayed physical interactions with both TFIIH and GAL4-VP16 through its coactivator domain, and these interactions were regulated distinctly by PC4 phosphorylation. Finally, GAL4-VP16 and PC4 stimulated both initiation and promoter escape to similar extents on the promoters with three and five GAL4 sites; however, they stimulated promoter escape preferentially on the promoter with a single GAL4 site. These results provide insight into the mechanism by which PC4 permits multiply bound GAL4-VP16 to attain synergy to achieve robust transcriptional activation.

[Molecular mechanism of vitamin K and its regulators in bone metabolism].

Two pathways that mediate vitamin K (VK) action in the bone metabolism have been identified. One pathway is well known mechanism, that mediates the posttranslational modification of the target proteins by VK dependent gamma-carboxylase (GGCX). The other pathway is a novel one, that mediates the transcriptional regulation of the target genes by SXR, steroid and xenobiotic receptor. Both mechanisms of VK are involved in modulation of extracellular matrix proteins in the bone.

Estrogen-responsive finger protein as a new potential biomarker for breast cancer.

PURPOSE: Estrogen-responsive finger protein (Efp) is a member of RING finger-B box-Coiled Coil family and is also a downstream target of estrogen receptor alpha. Previously, Efp was shown to mediate estrogen-induced cell growth, which suggests possible involvement in the development of human breast carcinomas. In this study, we examined expression of Efp in breast carcinoma tissues and correlated these findings with various clinicopathologic variables. EXPERIMENTAL DESIGN: Thirty frozen specimens of breast carcinomas were used for immunohistochemistry and laser capture microdissection/real-time PCR of Efp. Immunohistochemistry for Efp was also done in 151 breast carcinoma specimens fixed with formalin and embedded in paraffin wax. RESULTS: Efp immunoreactivity was detected in breast carcinoma cells and was significantly associated with the mRNA level (n = 30). Efp immunoreactivity was positively associated with lymph node status or estrogen receptor alpha status and negatively correlated with histologic grade or 14-3-3sigma immunoreactivity (n = 151). Moreover, Efp immunoreactivity was significantly correlated with poor prognosis of breast cancer patients, and multivariate analyses of disease-free survival and overall survival for 151 breast cancer patients showed that Efp immunoreactivity was the independent marker. CONCLUSIONS: Our data suggest that Efp immunoreactivity is a significant prognostic factor in breast cancer patients. These findings may account for an oncogenic role of Efp in the tumor progression of breast carcinoma.

[Role of estrogen signaling in male bone].

Although estrogen and its receptors (ERalpha and ERbeta) are requisite in male for functions such as reproductive tract, sexual behavior, maintenance of the skeleton, yet essential in female for normal functions. Genetically modified mouse models, and mutation research in human provide new insights for the roles of estrogen signaling in skeletal effects in both genders. Both of genders have androgen and estrogen, and also its receptors. In general, loss of sex steroid causes bone loss, on the other hand, addition of sex steroid maintain bone mass in both of sex. It seems that the differences are its quantity, balance, and expression patterns. The estrogen action regulates the transcription of estrogen responsive genes mediated by distinct estrogen receptors (ERalpha and ERbeta). So far, the mechanism of specific estrogen action is still not clear in bone remodeling in vivo . Here we discuss the role of estrogen signaling in male bone and its current topics of estrogen signaling.

Protein phosphatase 5 is a negative regulator of estrogen receptor-mediated transcription.

Estrogen receptors (ERs) are transcription factors that can be modulated by both estrogen-dependent and growth factor-dependent phosphorylation. A yeast two-hybrid screening identified a serine/threonine protein phosphatase (PP5) as an interactant of ERbeta (1-481), a dominant negative ERbeta mutant. Glutathione S-transferase pull-down assays, mammalian two-hybrid assays, and immunoprecipitation studies showed that PP5 directly binds to both ERalpha and ERbeta via its tetratricopeptide repeat domain. E domains of ERalpha and ERbeta, without containing activation domain core regions in transcription activation function 2, were required for the binding to PP5. In ERalpha-positive breast cancer MCF7 cells, estrogen- and epidermal growth factor-dependent phosphorylation of ERalpha on serine residue 118, a major phosphorylation site of the receptor, was reduced by expressing PP5 but enhanced by PP5 antisense oligonucleotide. Estrogen-induced transcriptional activities of both ERalpha and ERbeta and mRNA expression of estrogen-responsive genes, including pS2, c-myc, and cyclin D1, were suppressed by PP5 but enhanced by PP5 antisense oligonucleotide. A truncated PP5 mutant consisting only of its tetratricopeptide repeat domain acted as a dominant negative PP5 that enhanced serine residue 118 phosphorylation of ERalpha and transactivations by ERalpha and ERbeta. We present the first evidence that PP5 functions as an inhibitory regulator of ER phosphorylation and transcriptional activation in vivo.

Liver-specific γ-glutamyl carboxylase-deficient mice display bleeding diathesis and short life span.

Vitamin K is a fat-soluble vitamin that plays important roles in blood coagulation and bone metabolism. One of its functions is as a co-factor for γ-glutamyl carboxylase (Ggcx). Conventional knockout of Ggcx causes death shortly after birth in homozygous mice. We created Ggcx-floxed mice by inserting loxP sequences at the sites flanking exon 6 of Ggcx. By mating these mice with albumin-Cre mice, we generated Ggcx-deficient mice specifically in hepatocytes (Ggcx(Δliver/Δliver) mice). In contrast to conventional Ggcx knockout mice, Ggcx(Δliver/Δliver) mice had very low activity of Ggcx in the liver and survived several weeks after birth. Furthermore, compared with heterozygous mice (Ggcx(+/Δliver) ), Ggcx(Δliver/Δliver) mice had shorter life spans. Ggcx(Δliver/Δliver) mice displayed bleeding diathesis, which was accompanied by decreased activity of coagulation factors II and IX. Ggcx-floxed mice can prove useful in examining Ggcx functions in vivo.

Conditional expression of constitutively active estrogen receptor α in osteoblasts increases bone mineral density in mice.

Estrogen plays an important role in maintaining bone density in women. Estrogen receptor (ER) is expressed in osteoblasts and osteoclasts; however, the precise mechanism of ER in bone is not fully understood. In the present study, we generated a conditional transgenic mouse caERα(ColI) that expresses the constitutively active ERα in osteoblasts using collagen type I promoter-driven Cre transgenic mice. The caERα(ColI) mice showed increased bone mineral density (BMD). Osteoblasts prepared from caERα(ColI) mice expressed high levels of osteoprotegerin and decreased levels of IL-6, both of which are known to regulate osteoclast differentiation. These results suggest that ERα regulates osteoprotegerin and IL-6 production in osteoblasts and modulates BMD. The conditional transgenic mouse model is useful for understanding the in vivo function of ERα.

A ß-synuclein mutation linked to dementia produces neurodegeneration when expressed in mouse brain.

The discovery of α-synuclein (αS) mutations has made a major contribution to the understanding of the pathogenesis of α-synucleinopathies such as Parkinson's disease and dementia with Lewy bodies (DLB). In contrast, less attention has been paid to ß-synuclein (ßS) mutations. In this paper, we show that transgenic (tg) mice expressing DLB-linked P123H ßS develop progressive neurodegeneration, as characterized by axonal swelling, astrogliosis and behavioural abnormalities, with memory disorder being more prominent than motor deficits. Furthermore, cross-breeding of P123H ßS tg mice with αS tg mice, but not with αS knockout mice, greatly enhanced neurodegeneration phenotypes. These results suggest that P123H ßS is pathogenic and cooperates with pathogenic αS to stimulate neurodegeneration in mouse brain, indicating a causative role of P123H ßS in familial DLB. Given the neuritic pathology of ßS in sporadic α-synucleinopathies, it appears that alteration of ßS can contribute to the pathogenesis of a broad range of α-synucleinopathies.

Glutathione S-transferase theta 1 expressed in granulosa cells as a biomarker for oocyte quality in age-related infertility.

OBJECTIVE: The goal of this study was to identify a reliable biomarker for age-related infertility. DESIGN: Laboratory study. SETTING: ART laboratory. PATIENT(S): Patients undergoing intracytoplasmic sperm injection or IVF cycles. INTERVENTION(S): Expression of Glutathione S-transferase (GST) mRNA and protein in mural and cumulus granulosa cells obtained from infertile patients were examined by reverse transcriptase-polymerase chain reaction and immunofluorescence. MAIN OUTCOME MEASURE(S): Correlation between the expression of GST theta 1 (GSTT1) in granulosa cells and oocyte quality was a main outcome measure. RESULT(S): Expression of GSTT1 in granulosa cells from male factor patients was positively correlated with age and negatively with cumulus-oocyte complex maturity. When samples with high and low GSTT1 in granulosa cells were extracted from the other infertility factors, cumulus-oocyte complex maturity in the high GSTT1 group was significantly lower than that in the low GSTT1 group (high: 27.2% vs. low: 51.3%). The developmental capacity of oocytes in the high GSTT1 group was likely to be lower (high: 26.4% vs. low: 43.9%). Up-regulation of GSTT1 during aging may be promoted by FSH and H(2)O(2), determined by an in vitro model. CONCLUSION(S): GSTT1 is a good indicator for age-related infertility.

The fission yeast protein Ker1p is an ortholog of RNA polymerase I subunit A14 in Saccharomyces cerevisiae and is required for stable association of Rrn3p and RPA21 in RNA polymerase I.

A heterodimer formed by the A14 and A43 subunits of RNA polymerase (pol) I in Saccharomyces cerevisiae is proposed to correspond to the Rpb4/Rpb7 and C17/C25 heterodimers in pol II and pol III, respectively, and to play a role(s) in the recruitment of pol I to the promoter. However, the question of whether the A14/A43 heterodimer is conserved in eukaryotes other than S. cerevisiae remains unanswered, although both Rpb4/Rpb7 and C17/C25 are conserved from yeast to human. To address this question, we have isolated a Schizosaccharomyces pombe gene named ker1+ using a yeast two-hybrid system, including rpa21+, which encodes an ortholog of A43, as bait. Although no homolog of A14 has previously been found in the S. pombe genome, functional characterization of Ker1p and alignment of Ker1p and A14 showed that Ker1p is an ortholog of A14. Disruption of ker1+ resulted in temperature-sensitive growth, and the temperature-sensitive deficit of ker1delta was suppressed by overexpression of either rpa21+ or rrn3+, which encodes the rDNA transcription factor Rrn3p, suggesting that Ker1p is involved in stabilizing the association of RPA21 and Rrn3p in pol I. We also found that Ker1p dissociated from pol I in post-log-phase cells, suggesting that Ker1p is involved in growth-dependent regulation of rDNA transcription.

Alleviation of PC4-mediated transcriptional repression by the ERCC3 helicase activity of general transcription factor TFIIH.

Positive cofactor 4 (PC4), originally identified as a transcriptional coactivator, possesses the ability to suppress promoter-driven as well as nonspecific transcription via its DNA binding activity. Previous studies showed that the repressive activity of PC4 on promoter-driven transcription is alleviated by transcription factor TFIIH, possibly through one of its enzymatic activities. Using recombinant TFIIH, we have analyzed the role of TFIIH for alleviating PC4-mediated transcriptional repression and determined that the excision repair cross complementing (ERCC3) helicase activity of TFIIH is the enzymatic activity that alleviates PC4-mediated repression via beta-gamma bond hydrolysis of ATP. In addition, the alleviation does not require either ERCC2 helicase or cyclin-dependent kinase 7 kinase activity. We also show that, as complexed within TFIIH, the cyclin-dependent kinase 7 kinase does not possess the activity to phosphorylate PC4. Thus, TFIIH appears to protect promoters from PC4-mediated repression by relieving the topological constraint imposed by PC4 through the ERCC3 helicase activity rather than by reducing the repressive activity of PC4 via its phosphorylation.

Estrogen activates cyclin-dependent kinases 4 and 6 through induction of cyclin D in rat primary osteoblasts.

Estrogen plays important roles in maintaining bone density and protecting against osteoporosis, but the underlying mechanisms of estrogen action via estrogen receptors (ERs) in bone remain to be clarified. In the present study, we isolated primary osteoblasts derived from transgenic rats harboring a dominant negative ER mutant, rat ERalpha (1-535) cDNA, and from their wild-type littermates. We observed that the rate of cell growth of osteoblasts from the transgenic rats was reduced compared to that of wild-type osteoblasts. Utilizing cDNA microarray analysis, we found that mRNA level of cyclin D2 was lower in the osteoblasts from the transgenic rats. D-type cyclins including cyclin D1, cyclin D2, and cyclin D3 are cell cycle regulators that promote progression through the early-to-mid G1 phase of the cell cycle. The protein levels of D-type cyclins including cyclin D2 and cyclin D3 but not cyclin D1 were elevated in wild-type osteoblasts with 17beta-estradiol treatment, resulting in the activation of cyclin-dependent kinases 4 and 6 (Cdk4/6) activities and the promotion of cell growth. Moreover, an anti-estrogen ICI 182,780 abolished the induction of the expression of D-type cyclins by 17beta-estradiol. Our findings indicate that estrogen and its receptors enhance Cdk4/6 activities through the induction of D-type cyclins, leading to the growth promotion of osteoblasts.

Efp targets 14-3-3 sigma for proteolysis and promotes breast tumour growth.

Oestrogen exerts its influence on target organs through activating oestrogen receptors (ERs) and regulating downstream genes by means of their oestrogen-responsive elements. Efp, a target gene product of ER alpha, is a member of the RING-finger B-box coiled-coil (RBCC) motif family. Efp is predominantly expressed in various female organs as well as in breast cancers, and is thought to be essential for oestrogen-dependent cell proliferation and organ development Efp-disrupted mice display underdeveloped uteri and reduced oestrogen responsiveness. Here we show that Efp is a RING-finger-dependent ubiquitin ligase (E3) that targets proteolysis of 14-3-3 sigma, a negative cell cycle regulator that causes G2 arrest. We demonstrate that tumour growth of breast cancer MCF7 cells implanted in female athymic mice is reduced by treatment with antisense Efp oligonucleotide. Efp-overexpressing MCF7 cells in ovariectomized athymic mice generate tumours in the absence of oestrogen. Loss of Efp function in mouse embryonic fibroblasts results in an accumulation of 14-3-3 sigma, which is responsible for reduced cell growth. These data provide an insight into the cell-cycle machinery and tumorigenesis of breast cancer by identifying 14-3-3 sigma as a target for proteolysis by Efp, leading to cell proliferation.