Do classroom relationships moderate the association between peer defending in school bullying and social-emotional adjustment?

Peer defending has been shown to protect bullied peers from further victimization and social-emotional problems. However, research examining defending behavior has demonstrated positive and negative social-emotional adjustment effects for defending students themselves. To explain these mixed findings, researchers have suggested that associations between defending behavior and social-emotional adjustment may be buffered by protective factors (i.e., defender protection hypothesis) or exacerbated by vulnerability or risk factors (i.e., defender vulnerability hypothesis). Consistent with these hypotheses, the present study aimed to investigate whether relationships with teachers and peers would moderate the association between defending behavior and social-emotional adjustment. This three-wave longitudinal study examined the association between peer nominated defending behavior and later self-reported depressive symptoms and self-esteem in 848 Belgian students in Grades 4-6 (53% girls; Mage = 10.61 years, SD = 0.90 at Wave 1). Peer nominated positive and negative teacher-student relationships (i.e., closeness and conflict) and peer relationships (i.e., acceptance and rejection) were included as moderators. Clustered multiple linear regression analyses demonstrated that defending behavior did not predict later depressive symptoms (ß = -0.04, p = .80) or self-esteem (ß = -0.19, p = .42). The lack of these associations could be explained by the defender protection and vulnerability hypotheses. However, contrary to our expectations, teacher-student closeness and peer acceptance did not play a protective role in the association between defending behavior and social-emotional adjustment (ß = -1.48-1.46, p = .24-0.96). In addition, teacher-student conflict and peer rejection did not put defending students at risk for social-emotional maladjustment (ß = -1.96-1.57, p = .54-0.97). Thus, relationships with teachers and peers did not moderate the association between defending behavior and later depressive symptoms and self-esteem.

Treatment-specific risk of subsequent malignant neoplasms in five-year survivors of diffuse large B-cell lymphoma.

BACKGROUND: The introduction of rituximab significantly improved the prognosis of diffuse large B-cell lymphoma (DLBCL), emphasizing the importance of evaluating the long-term consequences of exposure to radiotherapy, alkylating agents and anthracycline-containing (immuno)chemotherapy among DLBCL survivors. METHODS: Long-term risk of subsequent malignant neoplasms (SMNs) was examined in a multicenter cohort comprising 2373 5-year DLBCL survivors treated at ages 15-61 years in 1989-2012. Observed SMN numbers were compared with expected cancer incidence to estimate standardized incidence ratios (SIRs) and absolute excess risks (AERs/10 000 person-years). Treatment-specific risks were assessed using multivariable Cox regression. RESULTS: After a median follow-up of 13.8 years, 321 survivors developed one or more SMNs (SIR 1.5, 95% CI 1.3-1.8, AER 51.8). SIRs remained increased for at least 20 years after first-line treatment (SIR ≥20-year follow-up 1.5, 95% CI 1.0-2.2, AER 81.8) and were highest among patients ≤40 years at first DLBCL treatment (SIR 2.7, 95% CI 2.0-3.5). Lung (SIR 2.0, 95% CI 1.5-2.7, AER 13.4) and gastrointestinal cancers (SIR 1.5, 95% CI 1.2-2.0, AER 11.8) accounted for the largest excess risks. Treatment with >4500 mg/m2 cyclophosphamide/>300 mg/m2 doxorubicin versus ≤2250 mg/m2/≤150 mg/m2, respectively, was associated with increased solid SMN risk (hazard ratio 1.5, 95% CI 1.0-2.2). Survivors who received rituximab had a lower risk of subdiaphragmatic solid SMNs (hazard ratio 0.5, 95% CI 0.3-1.0) compared with survivors who did not receive rituximab. CONCLUSION: Five-year DLBCL survivors have an increased risk of SMNs. Risks were higher for survivors ≤40 years at first treatment and survivors treated with >4500 mg/m2 cyclophosphamide/>300 mg/m2 doxorubicin, and may be lower for survivors treated in the rituximab era, emphasizing the need for studies with longer follow-up for rituximab-treated patients.

The how and the why of study choice processes in higher education: The role of parental involvement and the experience of having an authentic inner compass.

INTRODUCTION: Late adolescents differ in the degree to which they are thoroughly engaged in the study choice process and in the degree to which their choices are autonomous in nature. This study examined the unique and interactive roles of (a) parental involvement in the study choice process and (b) late adolescents' sense of having an authentic inner compass (AIC) in predicting their study choice decision-making. METHOD: A cross-sectional questionnaire study was conducted among 331 12th-grade adolescents from the Flemish part of Belgium (68.3% female; Mage = 18.04, SD = 0.48) in the spring of 2017 and 2018. RESULTS: Results of the latent sum and difference models revealed that late adolescents experiencing a stronger AIC and more need-supportive parental involvement showed more engagement in and autonomous regulation of the study choice process. In contrast, when experiencing more controlling parental involvement or uninvolvement, late adolescents showed more controlled regulation, with parental control also being linked to less commitment. Although mothers were perceived to be more involved than fathers, maternal and paternal involvement were equally strongly related to the study choice tasks. CONCLUSION: Overall, late adolescents' sense of having an AIC and parental involvement were related independently to the outcomes, with sense of having an AIC yielding the strongest associations.

Teachers' and children's perceptions about their relationships: examining the construct of dependency in the Greek sociocultural context.

This study examines teachers' and children's perceptions of dependency, and their linkages with other relationship dimensions, in a cultural context with a more collectivistic orientation. Additionally, it examines the factorial validity and reliability of the Greek version of the Child Appraisal of Relationship with Teacher Scale (CARTS) and teacher-child perceptions' convergence of relationship quality. Participants were 348 kindergarten students and 35 teachers from Greek kindergarten classrooms. The measures used were the Student-Teacher Relationship Scale (STRS) and CARTS. Results verified the factorial validity and internal consistency of the Greek CARTS. Results replicated previous findings suggesting a positive association between Closeness and Dependency in both teachers' and children's perceptions. The finding about the positive association between closeness and dependency in a cultural context with a more collectivistic orientation, challenges the cultural universality of the construct of dependency and highlights the need for a more in-depth examination of the construct of dependency.

Parenting, Effortful Control, and Adolescents' Externalizing Problem Behavior: Moderation by Dopaminergic Genes.

Research shows that genetics and effortful control play an important role in the link between parenting and problem behavior. However, little is known about how these factors act simultaneously. This article used a moderated mediation model to examine whether effortful control mediated the link between parenting and externalizing problem behavior, and whether dopaminergic genes (i.e., polygenic index score including DAT1, DRD2, DRD4, COMT) moderated this link. Two three-wave studies were conducted on community samples (adolescents: Study 1: N = 457; Mage = 15.74; Study 2: N = 221; Mage = 12.84). There was no mediation by effortful control, but a moderation by dopaminergic reactivity was observed. Despite inconsistent evidence, this article indicates that the development of externalizing problem behavior is subject to genetic characteristics and parenting.

RCT to evaluate the influence of adjuvant medical treatment of peritoneal endometriosis on the outcome of IVF.

STUDY QUESTION: Does a 3-month adjuvant hormonal treatment of mild peritoneal endometriosis after laparoscopic surgery influence the outcome of IVF stimulation in terms of number of mature oocytes obtained per cycle? SUMMARY ANSWER: Complementary medical treatment of mild peritoneal endometriosis does not influence the number of oocytes per treatment cycle. WHAT IS KNOWN ALREADY: Endometriosis is a disease known to be related to infertility. However, the influence of superficial endometriosis-and its treatment-is still a matter of debate. STUDY DESIGN, SIZE, DURATION: A prospective controlled, randomized, open label trial was performed between February 2012 and March 2014 and embryological and clinical outcomes were measured. Patients with laparoscopically diagnosed peritoneal endometriosis (n= 120) were treated by laser surgery after which they were sequentially randomized by computer-generated allocation to one of the two groups. The primary outcome of the trial was the number of Metaphase II (MII) oocytes. Sample size was chosen to detect a difference of two MII oocytes with a power of 80%. The control group (Group B) received the classical long protocol IVF stimulation, whereas the research group (Group A) had an additional pituitary suppression, of 3 months using a long-acting GnRH agonist, prior to IVF. PARTICIPANTS/ MATERIALS, SETTING, METHODS: A total of 120 patients were included in the study, 61 of them in the study group and 59 patients in the control group. One patient of the control group was lost to follow up leading to 58 evaluable patients. MAIN RESULTS AND THE ROLE OF CHANCE: There was no difference in terms of the number of MII oocytes obtained per cycle: 8.2 in both groups (difference in MII between A and B: 0.07 [-1.89; 2.04] 95% confidence interval (CI)). Pregnancy rate did not differ, being 39.3% for Group A (24 out of 61 patients) versus 39.7% for Group B (23 out of 58 patients) (95% CI around difference in pregnancy rate between A and B: -0.31% [-17.96%; 17.86%]). However, a significantly (P = 0.025) lower dose of FSH (2561 IU for Group A and 2303 IU for Group B, 95% CI around difference in FSH between B and A: -258.6 IU [-483.4 IU; -33.8 IU]) and a significantly (P = 0.004) shorter stimulation period (Group A 12.3 days and Group B 11.3 days, 95% CI around difference in stimulation period between B and A: -1.03 days [-1.73 days; -0.33 days]) were needed to reach adequate follicle maturation in the control group. LIMITATIONS, REASON FOR CAUTION: The validity of this study is limited to mild peritoneal endometriosis, and does not apply to ovarian endometriosis, which is also commonly seen in infertility patients. WIDER IMPLICATIONS OF THE FINDINGS: There is no indication for complementary medical treatment of peritoneal endometriosis in terms of IVF outcome. On the contrary, stimulation takes longer and requires a higher amount of medication. STUDY FUNDING/COMPETING INTERESTS: There was no external funding for this clinical trial in the IVF Center, AZ Jan Palfijn, Ghent. There are no competing interests to declare. TRIAL REGISTRATION NUMBER: EudraCT nr: 2012-000784-25. TRIAL REGISTRATION DATE: First registration on 29 February 2012 and re-entered on 23 August 2012, NCT01682642 (due to a change of staff). DATE OF FIRST PATIENT'S ENROLLMENT: 8 March 2012.

Depressive symptoms in adolescence: The role of perceived parental support, psychological control, and proactive control in interaction with 5-HTTLPR.

BACKGROUND: Parenting dimensions are associated with depressive symptoms in adolescents. We investigated the role of perceived parenting dimensions and gene-environment interactions between these perceived parenting dimensions and five well-known variable number of tandem repeats (VNTRs): 5-HTTLPR, STin2, DAT1, DRD4, and MAO-A, in depressive symptoms. METHODS: From a non-clinical sample of 1111 Belgian adolescents (mean age: 13.79 years, SD=.94; 51% boys), 1103 adolescents consented for genetic research. Five VNTRs were analyzed using DNA from saliva samples. Perceived parenting dimensions (i.e., support, proactive control, psychological control, punishment, and harsh punishment) were examined using self-report scales completed by adolescents and their parents. Depressive symptoms were investigated using the CES-D self-report scale. Statistical analyses were performed in R using linear regression. RESULTS: Parental support, as perceived by the adolescent, was negatively associated with depressive symptoms (CES-D) and psychological control was positively associated with these symptoms. The only interaction effect withstanding correction for multiple testing was observed for 5-HTTLPR and the difference in proactive control as perceived by adolescents in comparison to parents. Short-allele carriers showed more depressive symptoms when there was a higher discrepancy in proactive control as perceived by adolescents versus parents. CONCLUSIONS: Our results suggest that perceived parenting dimensions are associated with depressive symptoms, as measured by the CES-D. We only found modest evidence for 5-HTTLPR as a moderator in the association between the difference in perception of proactive control (adolescents vs. parents) and depressive symptoms.

Corifollitropin stimulation in combination with GnRH-antagonists after estradiol valerate pre-treatment. A pilot study on patientfriendly IVF.

OBJECTIVE: To demonstrate the feasibility of scheduling an IVF cycle, without disadvantages, in the new patient friendly stimulation protocol using the long acting Corifollitropin Alfa, in combination with GnRH-antagonist protection and GnRH-agonist triggering. STUDY DESIGN: Two groups of ten patients were admitted in the study. Both received the same stimulation protocol with Corifollitropin Alfa in combination with GnRH-antagonist protection. After ultrasound evaluation on day 7 individually dosed Menopur was added. For triggering final oocyte maturation GnRH-agonists were used. The only difference between the two groups was that in the study group, estradiol valerate 4 mg/day was given from day 25 of the preceding cycle for a period of 10 days, thus postponing the start of follicular growth. RESULTS: Scheduling the IVF stimulation by the administration of estradiol valerate 4 mg/day did not influence the hormonal curves, nor the embryological results in comparison to patients with the same stimulation, starting their stimulation at the beginning of menstruation. In this pilot study four out of ten patients turned out to be pregnant, demonstrating an acceptable pregnancy rate. CONCLUSION: The combination of estradiol valerate 4 mg/day pre-treatment with the novel combination of Corifollitropin Alfa stimulation with GnRH-antagonist protection, individually topped off with Menopur, and triggered with GnRH-agonist proved to be a safe, patient-friendly (limited number of injections in comparison to classical IVF) (Patil, 2014) and efficient alternative to classical IVF stimulation protocols, allowing patients - and doctors - to schedule the treatment cycle to their convenience.

Prospective study to assess fluid accumulation and tenosynovial changes in the aromatase inhibitor-induced musculoskeletal syndrome: 2-year follow-up data.

BACKGROUND: Aromatase inhibitors (AIs) frequently lead to the AI-induced musculoskeletal syndrome (AIMSS). Looking into its pathophysiology, 6 months of AI therapy thickens the tendon sheath with intra-articular fluid (IAF) retention and loss of grip strength. We here report 24-month follow-up data. PATIENTS AND METHODS: A prospective cohort study of 33 postmenopausal breast cancer patients received adjuvant endocrine therapy; 27 received an AI and 6 received tamoxifen. At baseline, 6 and 24 months patients had a rheumatologic examination, including a grip strength test, and magnetic resonance imaging of both hands and wrists. The primary end point was tenosynovial changes; secondary end points were changes in morning stiffness, grip strength and IAF. RESULTS: Twenty-three AI and 5 tamoxifen patients completed all investigations. Between month 6 and 24, IAF further increased in AI users (P = 0.04) but not in tamoxifen users, and grip strength further decreased in both groups. The worsened tenosynovial changes were strongly correlated with a decrease in grip strength. At 24 months, morning stiffness continued to be present in over a third of AI users. CONCLUSION: AIMSS represents a substantial problem in breast cancer patients. It is associated with tenosynovial changes, IAF retention, joint stiffness and loss of grip strength that do not improve with prolonged use.

Aromatase inhibitor-induced loss of grip strength is body mass index dependent: hypothesis-generating findings for its pathogenesis.

BACKGROUND: Our preliminary results showed that tenosynovial changes and decrease in grip strength are associated with the aromatase inhibitor-induced musculoskeletal syndrome (AIMSS). Here, we report the final results and assess the relationship between grip strength and body mass index (BMI). PATIENTS AND METHODS: We conducted a prospective study including postmenopausal early breast cancer patients receiving either an aromatase inhibitor (AI) or tamoxifen. Primary end point was change from baseline in tenosynovial abnormalities. Secondary end points were changes from baseline in morning stiffness, intra-articular fluid and grip strength and its association with BMI. RESULTS: After 6 months of therapy, 74% [95% confidence interval (CI) 51% to 89%] of AI-treated patients had worsened tenosynovial abnormalities, 56% (95% CI 34% to 75%) had increased intra-articular fluid, and 22% (95% CI 9% to 45%) had increased morning stiffness. Grip strength decreased 8% for the left hand (95% CI 2% to 21%) and 11% for the right (95% CI 4% to 17%). Regression analysis suggested that grip strength decreased more for subjects with high or with low BMI. CONCLUSIONS: AIMSS is characterized by tenosynovial changes, intra-articular fluid and morning stiffness. We hypothesize that the quadratic association between BMI and loss of grip strength reflects AI-induced changes on the endocrine control of the growth hormone insulin-like growth factor-I pathway.

Smad-interacting protein 1 is a repressor of liver/bone/kidney alkaline phosphatase transcription in bone morphogenetic protein-induced osteogenic differentiation of C2C12 cells.

Up-regulation of liver/bone/kidney alkaline phosphatase (LBK-ALP) has been associated with the onset of osteogenesis in vitro. Its transcription can be up-regulated by bone morphogenetic proteins (BMPs), constitutively active forms of their cognate receptors, or appropriate Smads. The promoter of LBK-ALP has been characterized partially, but not much is known about its transcriptional modulation by BMPs. A few Smad-interacting transcriptional factors have been isolated to date. One of them, Smad-interacting protein 1 (SIP1), belongs to the family of two-handed zinc finger proteins binding to E2-box sequences present, among others, in the promoter of mouse LBK-ALP. In the present study we investigated whether SIP1 could be a candidate regulator of LBK-ALP transcription in C2C12 cells. We demonstrate that SIP1 can repress LBK-ALP promoter activity induced by constitutively active Alk2-Smad1/Smad5 and that this repression depends on the binding of SIP1 to the CACCT/CACCTG cluster present in this promoter. Interestingly, SIP1 and alkaline phosphatase expression domains in developing mouse limb are mutually exclusive, suggesting the possibility that SIP1 could also be involved in the transcriptional regulation of LBK-ALP in vivo. Taken together, these results offer an intriguing possibility that ALP up-regulation at the onset of BMP-induced osteogenesis could involve Smad/SIP1 interactions, resulting in the derepression of that gene.

Transforming growth factor beta signalling in vitro and in vivo: activin ligand-receptor interaction, Smad5 in vasculogenesis, and repression of target genes by the deltaEF1/ZEB-related SIP1 in the vertebrate embryo.

The identification and characterization of components of the transforming growth factor beta (TGFbeta) signalling pathway are proceeding at a very fast pace. To illustrate a number of our activities in this field, we first summarize our work aiming at the selection from a large collection of single residue substitution mutants of two activin A polypeptides in which D27 and K102, respectively, have been modified. This work has highlighted the importance of K102 and its positive charge for binding to activin type II receptors. Activin K102E, which did not bind to high-affinity receptor complexes, may be a valuable beta chain, when incorporated in recombinant inhibin to unambiguously detect novel inhibin binding sites at the cell surface. We then illustrate how Smad5 knockout mice and an overexpression approach with a truncated TGFbeta type II receptor in the mouse embryo can contribute to the identification of a novel TGFbeta-->TbetaRII/ALK1-->Smad5 pathway in endothelial cells in the embryo proper and the yolk sac vasculature. We conclude with a summary of our results with a Smad-interacting transcriptional repressor but focus on its biological significance in the vertebrate embryo.

Structure of the Bacillus cell fate determinant SpoIIAA in phosphorylated and unphosphorylated forms.

BACKGROUND: The asymmetric cell division during sporulation in Bacillus subtilis gives rise to two compartments: the mother cell and the forespore. Each follow different programs of gene expression coordinated by a succession of alternate RNA polymerase sigma factors. The activity of the first of these sigma factors, sigmaF, is restricted to the forespore although sigmaF is present in the predivisional cell and partitions into both compartments following the asymmetric septation. For sigmaF to become active, it must escape from a complex with its cognate anti-sigma factor, SpoIIAB. This relief from SpoIIAB inhibition requires the dephosphorylation of the anti-sigma factor antagonist, SpoIIAA. The phosphorylation state of SpoIIAA is thus a key determinant of sigmaF activity and cell fate. RESULTS: We have solved the crystal structures of SpoIIAA from Bacillus sphaericus in its phosphorylated and unphosphorylated forms. The overall structure consists of a central beta-pleated sheet, one face of which is buried by a pair of alpha helices, while the other is largely exposed to solvent. The site of phosphorylation, Ser57, is located at the N terminus of helix alpha2. The phosphoserine is exceptionally well defined in the 1.2 A electron density maps, revealing that the structural changes accompanying phosphorylation are slight. CONCLUSIONS: Comparison of unphosphorylated and phosphorylated SpoIIAA shows that covalent modification has no significant effect on the global structure of the protein. The phosphoryl group has a passive role as a negatively charged flag rather than the active role it plays as a nucleus of structural reorganization in many eukaryotic signaling systems.

The two-handed E box binding zinc finger protein SIP1 downregulates E-cadherin and induces invasion.

Transcriptional downregulation of E-cadherin appears to be an important event in the progression of various epithelial tumors. SIP1 (ZEB-2) is a Smad-interacting, multi-zinc finger protein that shows specific DNA binding activity. Here, we report that expression of wild-type but not of mutated SIP1 downregulates mammalian E-cadherin transcription via binding to both conserved E2 boxes of the minimal E-cadherin promoter. SIP1 and Snail bind to partly overlapping promoter sequences and showed similar silencing effects. SIP1 can be induced by TGF-beta treatment and shows high expression in several E-cadherin-negative human carcinoma cell lines. Conditional expression of SIP1 in E-cadherin-positive MDCK cells abrogates E-cadherin-mediated intercellular adhesion and simultaneously induces invasion. SIP1 therefore appears to be a promoter of invasion in malignant epithelial tumors.

SIP1 (Smad interacting protein 1) and deltaEF1 (delta-crystallin enhancer binding factor) are structurally similar transcriptional repressors.

BACKGROUND: Smad proteins are intracellular mediators of transforming growth factor-beta (TGFbeta) signalling that regulate gene expression by interacting with different classes of transcription factors including DNA-binding multi-zinc finger proteins. One of these, Smad interacting protein 1 (SIP1), is a novel two-handed zinc-finger protein that displays strong similarity with the transcriptional repressor delta-crystallin enhancer binding factor (deltaEF1). Here, we summarize what is known about the mechanism of action of both proteins and their role in vertebrate embryogenesis. Our data are discussed together with the present knowledge on other zinc-finger containing Smad interacting proteins. METHODS: The activities and function of SIP1 have been analysed through documentation of expression patterns, the effect of over-expression of SIP1 on target-gene expression, and promoter studies using Xenopus embryos. Moreover, S1P1/Smad complexes and their association with target promoter DNA were analyzed in biochemical studies. RESULTS: SIP1 is a transcriptional repressor displaying overlapping DNA binding specificities with deltaEF1. An in vivo target of SIP1 in Xenopus is a gene required for the formation of mesoderm, Brachyury (XBra). Our data indicate that SIP1 is required to confine XBra gene expression to the mesoderm. Furthermore, the expression pattern in Xenopus invites us to speculate that SIP1 plays a role in specification/differentiation of neuroectoderm. Unlike deltaEF1, SIP1 can bind directly to activated receptor regulated Smads (R-Smads) and recruit them to the DNA. This indicates that Smads may modulate the activity of SIP1 as a transcriptional repressor. CONCLUSIONS: Our data point to a role of SIP1 in developmental processes regulated by members of the TGFbeta family such as induction of mesoderm (mediated through activin-like signalling) and inhibition of neuroectoderm formation (mediated by bone morphogenetic proteins [BMPs]). Whereas SIP1 could act in TGFbeta signal transduction by virtue of interaction with activated R-Smads, genetic studies in the mouse indicate that deltaEF1 may act in certain TGFbeta pathways-i.e., BMPs and growth and differentiation factors (GDFs)-as well. The molecular mechanisms by which these transcriptional repressors act, as well as the function of the SIP1/Smad interaction, remain to be elucidated. CLINICAL RELEVANCE: Mutations in components of the TGFbeta signalling pathways have been associated with disease and congenital malformations. We anticipate that identification of Smad interacting transcription factors including SIP1 and their targets will help us to understand the molecular basis of certain pathologies.

Self-representations and socioemotional competence in young children: a 3-year longitudinal study.

In a longitudinal study, the connections between children's self-representations at age 5 and their self-perceptions, socioemotional competence according to the teacher, and peer acceptance at age 8 were examined. The sample consisted of 60 children (33 boys, 27 girls). Self-representations at age 5 were assessed by the Puppet Interview (J. Cassidy, 1988). Results generally revealed the expected connections between the positiveness of self at age 5 and self-perceptions and socioemotional functioning 3 years later. These findings support the predictive validity of the Puppet Interview. Moreover, they suggest that young children do possess at least a rudimentary sense of being generally worthy and lovable, which can be assessed by using adequate, age-appropriate interviews.

Crystallization of full-length CysB of Klebsiella aerogenes, a LysR-type transcriptional regulator.

CysB is a positive regulator of transcription of genes involved in cysteine biosynthesis in Gram-negative bacteria and belongs to the large family of LysR-type transcriptional regulators. The full-length protein from Klebsiella aerogenes has been crystallized from solutions containing PEG 8000 in the presence and in the absence of the inducer N-acetylserine by the method of vapour diffusion in hanging drops. For the complexed protein different crystal forms appear in the same drops.

The bone morphogenetic protein 2 signaling mediator Smad1 participates predominantly in osteogenic and not in chondrogenic differentiation in mesenchymal progenitors C3H10T1/2.

The role of the bone morphogenetic protein (BMP)-signaling mediator Smad1 in osteogenic or chondrogenic differentiation was investigated in murine parental mesenchymal progenitors C3H10T1/2 and its derivatives constitutively expressing BMP-2 (C3H10T1/2-BMP-2) and, therefore, undergo BMP-mediated osteogenic/ chondrogenic development. The functions of the three Smad1 domains, that is, the N-terminal (MH1) domain, the C-terminal (MH2) domain, and the midregional proline-rich linker domain, were documented and compared with full-length Smadl. We showed that expression of the MH2 domain in parental C3H10T1/2 cells was sufficient to initiate osteogenic differentiation. Interestingly, MH1 was sufficient to initiate transcription of osteogenic marker genes like the osteocalcin or parathyroid hormone/parathyroid hormone-related protein (PTH/PTHrP) receptor. However, MH1 interfered with the histologically distinct formation of osteoblast-like cells. A dominant-negative effect on MH2-mediated osteogenic development in C3H10T1/2 cells was observed by the dose-dependent trans-expression of the midregional linker domain. Importantly, in contrast to osteogenic differentiation, Smad1 and its domains do not mimic or interfere with BMP-2-dependent chondrogenic development as monitored by the inability of MH2 to give rise to histologically distinct chondrocytes in parental C3H10T1/2 cells and by the inefficiency of the MH1 or linker domain to interfere with BMP-2-mediated chondrogenic differentiation.

New mode of DNA binding of multi-zinc finger transcription factors: deltaEF1 family members bind with two hands to two target sites.

SIP1, a Smad-interacting protein, and deltaEF1, a transcriptional repressor involved in skeletal and T-cell development, belong to the same family of DNA binding proteins. SIP1 and deltaEF1 contain two separated clusters of zinc fingers, one N-terminal and one C-terminal. These clusters show high sequence homology and are highly conserved between SIP1 and deltaEF1. Each zinc finger cluster binds independently to a 5'-CACCT sequence. However, high-affinity binding sites for full-length SIP1 and deltaEF1 in the promoter regions of candidate target genes like Xenopus Xbra2, and human alpha4-integrin and E-cadherin, are bipartite elements composed of one CACCT and one CACCTG sequence, the orientation and spacing of which can vary. Using transgenic Xenopus embryos, we demonstrate that the integrity of these two sequences is necessary for correct spatial expression of a Xbra2 promoter-driven reporter gene. Both zinc finger clusters must be intact for the high-affinity binding of SIP1 to DNA and for its optimal repressor activity. Our results show that SIP1 binds as monomer and contacts one target sequence with the first zinc finger cluster, and the other with the second cluster. Our work redefines the optimal binding site and, consequently, candidate target genes for vertebrate members of the deltaEF1 family.

SIP1, a novel zinc finger/homeodomain repressor, interacts with Smad proteins and binds to 5'-CACCT sequences in candidate target genes.

Activation of transforming growth factor beta receptors causes the phosphorylation and nuclear translocation of Smad proteins, which then participate in the regulation of expression of target genes. We describe a novel Smad-interacting protein, SIP1, which was identified using the yeast two-hybrid system. Although SIP1 interacts with the MH2 domain of receptor-regulated Smads in yeast and in vitro, its interaction with full-length Smads in mammalian cells requires receptor-mediated Smad activation. SIP1 is a new member of the deltaEF1/Zfh-1 family of two-handed zinc finger/homeodomain proteins. Like deltaEF1, SIP1 binds to 5'-CACCT sequences in different promoters, including the Xenopus brachyury promoter. Overexpression of either full-length SIP1 or its C-terminal zinc finger cluster, which bind to the Xbra2 promoter in vitro, prevented expression of the endogenous Xbra gene in early Xenopus embryos. Therefore, SIP1, like deltaEF1, is likely to be a transcriptional repressor, which may be involved in the regulation of at least one immediate response gene for activin-dependent signal transduction pathways. The identification of this Smad-interacting protein opens new routes to investigate the mechanisms by which transforming growth factor beta members exert their effects on expression of target genes in responsive cells and in the vertebrate embryo.