Oncogenic and Tumor Suppressor Functions for Lymphoid Enhancer Factor 1 in E2a-/- T Acute Lymphoblastic Leukemia.

T lymphocyte acute lymphoblastic leukemia (T-ALL) is a heterogeneous disease affecting T cells at multiple stages of their development and is characterized by frequent genomic alterations. The transcription factor LEF1 is inactivated through mutation in a subset of T-ALL cases but elevated LEF1 expression and activating mutations have also been identified in this disease. Here we show, in a murine model of T-ALL arising due to E2a inactivation, that the developmental timing of Lef1 mutation impacts its ability to function as a cooperative tumor suppressor or oncogene. T cell transformation in the presence of LEF1 allows leukemic cells to become addicted to its presence. In contrast, deletion prior to transformation both accelerates leukemogenesis and results in leukemic cells with altered expression of genes controlling receptor-signaling pathways. Our data demonstrate that the developmental timing of Lef1 mutations impact its apparent oncogenic or tumor suppressive characteristics and demonstrate the utility of mouse models for understanding the cooperation and consequence of mutational order in leukemogenesis.

Deletion of IKK2 in haematopoietic cells of adult mice leads to elevated interleukin-6, neutrophilia and fatal gastrointestinal inflammation.

The IκB kinase complex, consisting of IKK1, IKK2 and the regulatory subunit NEMO, is required for NF-κB signalling following the activation of several cell surface receptors, such as members of the Tumour Necrosis Factor Receptor superfamily and the Interleukin-1 Receptor. This is critical for haematopoietic cell proliferation, differentiation, survival and immune responses. To determine the role of IKK in the regulation of haematopoiesis, we used the Rosa26Cre-ERT2 Cre/lox recombination system to achieve targeted, haematopoietic cell-restricted deletion of the genes for IKK1 or IKK2 in vivo. We found that the IKK complex plays a critical role in haematopoietic cell development and function. Deletion of IKK2, but not loss of IKK1, in haematopoietic cells led to an expansion of CD11b/Gr-1-positive myeloid cells (neutrophilia), severe anaemia and thrombocytosis, with reduced numbers of long-term haematopoietic stem cells (LT-HSCs), short-term haematopoietic stem cells (ST-HSCs) and multipotential progenitor cells (MPPs), increased circulating interleukin-6 (IL-6) and severe gastrointestinal inflammation. These findings identify distinct functions for the two IKK catalytic subunits, IKK1 and IKK2, in the haematopoietic system.

Cutting Edge: Lymphomyeloid-Primed Progenitor Cell Fates Are Controlled by the Transcription Factor Tal1.

Lymphoid specification is the process by which hematopoietic stem cells (HSCs) and their progeny become restricted to differentiation through the lymphoid lineages. The basic helix-loop-helix transcription factors E2A and Lyl1 form a complex that promotes lymphoid specification. In this study, we demonstrate that Tal1, a Lyl1-related basic helix-loop-helix transcription factor that promotes T acute lymphoblastic leukemia and is required for HSC specification, erythropoiesis, and megakaryopoiesis, is a negative regulator of murine lymphoid specification. We demonstrate that Tal1 limits the expression of multiple E2A target genes in HSCs and controls the balance of myeloid versus T lymphocyte differentiation potential in lymphomyeloid-primed progenitors. Our data provide insight into the mechanisms controlling lymphocyte specification and may reveal a basis for the unique functions of Tal1 and Lyl1 in T acute lymphoblastic leukemia.

Characterization of Blimp-1 function in effector regulatory T cells.

Regulatory T (Treg) cells maintain immunological tolerance in steady-state and after immune challenge. Activated Treg cells can undergo further differentiation into an effector state that highly express genes critical for Treg cell function, including ICOS, TIGIT and IL-10, although how this process is controlled is poorly understood. Effector Treg cells also specifically express the transcriptional regulator Blimp-1 whose expression overlaps with many of the canonical markers associated with effector Treg cells, although not all ICOS+TIGIT+ Treg cells express Blimp-1 or IL-10. In this study, we addressed the role of Blimp-1 in effector Treg cell function. Mice lacking Blimp-1 specifically in Treg cells mature normally, but succumb to a multi-organ inflammatory disease later in life. Blimp-1 is not required for Treg cell differentiation, with mutant mice having increased numbers of effector Treg cells, but regulated a suite of genes involved in cell signaling, communication and survival, as well as being essential for the expression of the immune modulatory cytokine IL-10. Thus, Blimp-1 is a marker of effector Treg cells in all contexts examined and is required for the full functionality of these cells during aging.

Effector Regulatory T Cell Differentiation and Immune Homeostasis Depend on the Transcription Factor Myb.

FoxP3-expressing regulatory T (Treg) cells are essential for maintaining immune homeostasis. Activated Treg cells undergo further differentiation into an effector state that highly expresses genes critical for Treg cell function, although how this process is coordinated on a transcriptional level is poorly understood. Here, we demonstrate that mice lacking the transcription factor Myb in Treg cells succumbed to a multi-organ inflammatory disease. Myb was specifically expressed in, and required for the differentiation of, thymus-derived effector Treg cells. The combination of transcriptome and genomic footprint analyses revealed that Myb directly regulated a large proportion of the gene expression specific to effector Treg cells, identifying Myb as a critical component of the gene regulatory network controlling effector Treg cell differentiation and function.

Ginástica laboral: compreendendo a baixa adesão pela óptica do funcionário / Labor gym: understanding the low adhesion by the employee standpoint

Introdução: A Ginástica Laboral (GL) tem contribuído, nos últimos tempos, para a melhoria no funcionamento da empresa e na saúde do trabalhador. O presente estudo busca desmistificar por que trabalhadores que, voluntariamente, solicitam ou aceitam participar de um programa de ginástica laboral apresentam baixa adesão às práticas, quando as mesmas lhes são oferecidas. Objetivo: Compreender a baixa adesão da ginástica laboral, pela óptica do funcionário. Método: O estudo baseia-se numa abordagem de pesquisa qualitativa, realizada na cidade de Maceió em 2013, por meio de entrevistas semiestruturadas, com funcionários de uma empresa que trabalham na área de comunicação. Resultados: Foi constatado que muitos dos funcionários não têm a real compreensão dos benefícios que a ginástica laboral proporciona na prevenção de doenças ocupacionais, ocasionando, assim, a baixa adesão por não interromperem suas atividades por alguns minutos para a realização da ginástica. Diante do exposto, é necessário que a empresa e os profissionais que atuam neste meio busquem instrumentos para elaboração de estratégias que melhorem a adesão às práticas da Ginástica Laboral. Conclusão: Através das entrevistas, pode-se atestar, nesta empresa, que muitos dos funcionários possuem uma baixa adesão ao programa de GL por não compreenderem os reais benefícios da mesma. (AU)

Introduction: The Workplace exercise has contributed lately to improve the functioning of the company and the worker health. This study searches to demystify why we find poor adherence of workers to a workplace exercise program even after requesting or accepting to participate in this program. Aim: To focus on understanding the little interest in exercise from the employee perspective. Method: The study, carried out in the city of Maceió in 2013, is based on a qualitative research approach, using semi-structured interviews with employees who work in a communication company. Results: Many of the staff has no real understanding of the benefits that exercise provides for the prevention of occupational diseases. Thus, they do not interrupt their work activities for a few minutes to do the exercises. Based on the above considerations, it is necessary that the company and the physical education professional together seek solutions to planning strategies and improve the interest for the workplace exercises practices. (AU)

Anatomo-radiographic description of the axial skeleton of the crab-eating fox (Cerdocyon thous) / Descrição anátomo-radiográfica do esqueleto axial do cachorro-do-mato (Cerdocyon thous)

The aim of this study was to describe the axial skeleton of a wild Brazilian carnivorous, the crab-eating fox (Cerdocyon thous). Five specimens of crab-eating fox were previously unfrozen for radiographic exams and their bones went through dissection and chemical maceration. This animal presents seven cervical vertebrae, and from the third on, they become shorter and wider than the other ones e the spinous process was makeable from the fifth cervical vertebrae on. There are thirteen thoracic vertebrae and the spinous process of the lumbar vertebrae, which are seven, decreases from the fifth on. The sacrum is formed by two vertebrae and there are twenty or twenty one caudal vertebrae. It can be concluded that the crab-eating fox axial skeleton is similar to that of the domestic dog.(AU)

O objetivo deste trabalho foi descrever o esqueleto axial de um carnívoro selvagem brasileiro, o cachorro-do-mato (Cerdocyon thous). Cinco animais foram previamente descongelados para exames radiográficos e posteriormente submetidos a dissecação óssea e maceração química. Os animais apresentavam sete vértebras cervicais e, à partir da terceira, eram mais curtas e largas e o processo espinhoso mais evidente a partir da quinta vértebra cervical. Há treze vértebras torácicas e o processo espinhoso das vértebras lombares, que são sete, diminui partir da quinta vértebra. O sacro é constituído por duas vértebras fundidas e há 20 ou 21 vértebras caudais. Pode-se concluir que o esqueleto axial do cachorro-do-mato se assemelha ao do cão doméstico.(AU)

Inhibitors of DNA binding proteins restrict T cell potential by repressing Notch1 expression in Flt3-negative common lymphoid progenitors.

Lineage commitment is regulated during hematopoiesis, with stepwise loss of differentiation potential ultimately resulting in lineage commitment. In this study we describe a novel population of B/NK bipotent precursors among common lymphoid progenitors in the fetal liver and the bone marrow. The absence of T cell precursor potential, both in vivo and in vitro, is due to low Notch1 expression and secondary to inhibition of E2A activity by members of the inhibitor of DNA binding (Id) protein family. Our results demonstrate a new, Id protein-dependent, molecular mechanism of Notch1 repression, operative in both fetal and adult common lymphoid progenitors, where T cell potential is selectively inhibited without affecting either the B or NK programs. This study identifies Id proteins as negative regulators of T cell specification, before B and NK commitment, and provides important insights into the transcriptional networks orchestrating hematopoiesis.

Raloxifene therapy inhibits osteoclastogenesis during the alveolar healing process in rats.

OBJECTIVE: To investigate the expression of OPG, RANKL and TRAP during alveolar healing process (7, 14, 21, 28 and 42 postoperative days) in ovariectomized rats treated with raloxifene or with oestrogen replacement therapy, using immunohistochemistry reaction approach. MATERIALS AND METHODS: Wistar female rats (10 weeks age) were submitted to ovariectomy surgery (OVX) or sham surgery. The female rats were divided in four groups: (1) sham; (2) OVX/O (ovariectomy and oil); (3) OVX/E2 (ovariectomy and oestrogen replacement); (4) OVX/RLX (ovariectomy and raloxifene therapy). RESULTS: It was observed high amount of OPG immunolabelling with predominance at 14 and 21 postoperative days on sham and OVX/RLX groups, respectively. At 7 postoperative days, there was no difference between the groups for TRAP protein. Otherwise, to the other periods, it was observed greater expression of TRAP and RANKL protein on OVX/O group compared to sham, OVX/E2 and OVX/RLX groups. It was also observed a discrete TRAP immunolabelling at 28 and 42 postoperative days on OVX/RLX group. CONCLUSIONS: Oestrogen deficiency induces osteoclastogenesis in the alveolar healing process. Quantitative changes in the osteoclastic activity could be prevented through the raloxifene therapy.

Action of nicotine and ovariectomy on bone regeneration after tooth extraction in rats.

PURPOSE: The purpose of this study was to evaluate the effects of nicotine and ovariectomy on alveolar bone regeneration after exodontias in rats. MATERIALS AND METHODS: For 30 days, sham ovariectomized (OVX)/NaCl, sham OVX/nicotine, OVX/NaCl, and OVX/nicotine animals were given 2 daily injections of saline or hemisulfate of nicotine. After this period, exodontic procedures were carried out and treatment continued up to the time of euthanasia on days 7 and 14 when the alveoli were removed for further analyses. RESULTS: The data confirmed that nicotine significantly delays the alveolar regeneration process after dental extraction in rats and showed that the association of nicotine with ovariectomy exacerbates these results. CONCLUSION: These results indicate that nicotine potentiated the effect of estrogen deficiency on bone regeneration induced by ovariectomy.

Reduced EBF expression underlies loss of B-cell potential of hematopoietic progenitors with age.

Aging is accompanied by a reduction in the generation of B lymphocytes leading to impaired immune responses. In this study, we have investigated whether the decline in B lymphopoiesis is due to age-related defects in the hematopoietic stem cell compartment. The ability of hematopoietic stem cells from old mice to generate B cells, as measured in vitro, is decreased 2-5-fold, while myeloid potential remains unchanged. This age-related decrease in B-cell potential is more marked in common lymphoid progenitors (CLP) and was associated with reduced expression of the B-lineage specifying factors, EBF and Pax5. Notably, retrovirus-mediated expression of EBF complemented the age-related loss of B-cell potential in CLP isolated from old mice. Furthermore, transduction of CLP from old mice with a constitutively active form of STAT5 restored both EBF and Pax5 expression and increased B-cell potential. These results are consistent with a mechanism, whereby reduced expression of EBF with age decreases the frequency with which multipotent hematopoietic progenitors commit to a B-cell fate, without altering their potential to generate myeloid cells.

Histomorphometric analysis and immunolocalization of RANKL and OPG during the alveolar healing process in female ovariectomized rats treated with oestrogen or raloxifene.

OBJECTIVE: To investigate the effects of bone-resorption inhibitors (oestrogen and raloxifene) on the RANKL/OPG balance during the chronology of the alveolar healing process in ovariectomized (OVX) rats by means of immunocolocalization and histomorphometric analysis. MATERIALS AND METHODS: One hundred sixty female Wistar rats at 70 days of age were either OVX or sham-operated and divided into four groups: sham, OVX/Oil, OVX with E(2) replacement (17beta-estradiol, 400 microg/month), OVX with RLX treatment (1mg/kg bw/day). The 60-day treatment started 8 days after ovariectomy. The incisors were extracted to allow analysis of 7, 14, 21, 28 and 42 days of wound healing. After obtaining the histological samples, slides were stained with hematoxylin and eosin or subjected to immunocolocalization reaction for RANKL and OPG. Results were quantitatively evaluated. RESULTS: Histomorphometric analysis showed that the sham group presented the highest and OVX/Oil group the lowest mean bone formation value in the post-extraction period. The immunocolocalization analysis showed a larger increase in bone turnover at 7 postoperative days in OVX/Oil and sham groups and decreasing bone turnover in the other periods. The OVX/Oil group showed a large decrease in bone turnover at 14 postoperative days, a period demonstrated by mild cellular activity. OVX/E(2) and sham groups showed a decreased bone turnover at 28 postoperative days while OVX/RLX group showed a decreased bone turnover at 21 postoperative days. On the 42nd postoperative day, sham and OVX/RLX groups showed an established alveolar bone healing process. CONCLUSIONS: Ovariectomy delays the alveolar healing process and interferes with bone turnover through the balance between RANKL and OPG. Oestrogen replacement or raloxifene treatment did not totally recover the oestrogen-deficient state. However raloxifene treatment showed more satisfactory results than oestrogen replacement.

Osteocalcin immunolabeling during the alveolar healing process in ovariectomized rats treated with estrogen or raloxifene.

The influence of an estrogen-deficient state was evaluated in this study and also its treatments with estrogen (E(2)) or with raloxifene (RLX) on the expression of osteocalcin during the periods of the chronology of the alveolar bone healing process (7, 14, 21, 28 and 42 post-extraction days) by means of immunohistochemistry reactions and histomorphometric analysis. Rats (200-220 g) with oestrus cycles normal were either OVX or sham-operated and divided into four groups: sham, OVX control (OVX/O), estrogen (OVX/E(2); 17 beta-estradiol, 400 microg/mo) and raloxifene (OVX/RLX; 1 mg/kg bw/d) groups. Histomorphometric analysis showed the sham group presented the highest mean value of bone formation post-extraction. The reaction of immunohistochemistry for osteocalcin presented stronger expression of osteocalcin with predominance at 14 and 21 days on sham group. The OVX/RLX group presented better results than OVX/E(2), considering the expression of osteocalcin in osteoblastic lineage cells, but still inferior than the sham group. It was concluded that ovariectomy decreases the mineralization process and the osteocalcin expression during the chronology of the alveolar healing process that is not totally recovered with estrogen replacement or raloxifene treatment.

A s-myly route toward lymphoid differentiation.

In this issue of Immunity, Ng et al. (2009) show that lymphoid-lineage priming occurs in hematopoietic stem cells and is dependent on the Ikaros transcription factor, as is repression of self-renewal genes during lymphoid differentiation.

Transcriptional regulation of lymphocyte development.

B lymphocytes and T lymphocytes develop from hematopoietic stem cells through a series of intermediates with progressively decreased lineage differentiation potential. Differentiation is preceded by increased accessibility of the chromatin at genes that are poised for expression in the progeny of a multipotent cell. During the process of differentiation there is increased expression of lineage-associated genes and repression of lineage-inappropriate genes resulting in commitment to differentiation through a specific lineage. These transcriptional events are coordinated by networks of transcription factors and their associated chromatin remodeling factors. The B lymphocyte lineage provides a paradigm for how these events unfold to promote specification and commitment to a single developmental pathway.

E2A proteins promote development of lymphoid-primed multipotent progenitors.

The first lymphoid-restricted progeny of hematopoietic stem cells (HSCs) are lymphoid-primed multipotent progenitors (LMPPs), which have little erythromyeloid potential but retain lymphoid, granulocyte, and macrophage differentiation capacity. Despite recent advances in the identification of LMPPs, the transcription factors essential for their generation remain to be identified. Here, we demonstrated that the E2A transcription factors were required for proper development of LMPPs. Within HSCs and LMPPs, E2A proteins primed expression of a subset of lymphoid-associated genes and prevented expression of genes that are not normally prevalent in these cells, including HSC-associated and nonlymphoid genes. E2A proteins also restricted proliferation of HSCs, MPPs, and LMPPs and antagonized differentiation of LMPPs toward the myeloid fate. Our results reveal that E2A proteins play a critical role in supporting lymphoid specification from HSCs and that the reduced generation of LMPPs underlies the severe lymphocyte deficiencies observed in E2A-deficient mice.

Interleukin-7 is necessary to maintain the B cell potential in common lymphoid progenitors.

Interleukin-7 (IL-7) promotes survival and expansion of lymphoid precursors. We show here that, in addition, IL-7 has a fundamental role, as early as the stage of the multipotent (B/T/NK) common lymphoid progenitor (CLP), in maintaining the B cell differentiation program open. CLPs generated in the absence of IL-7 have normal T/NK differentiation potential, but severely impaired B potential. Accordingly, CLPs from IL-7-deficient mice express lower amounts of early B cell factor (EBF) and Pax5 than wild-type CLPs, but similar amounts of GATA-3. Importantly, induced overexpression of EBF is sufficient to restore the B potential in these cells. These results indicate that IL-7 directs commitment of CLPs by modulating EBF expression. This is the first example of a cytokine influencing lymphoid lineage commitment in multipotent progenitors and highlights the relevance of the expression of a functional IL-7 receptor at the CLP stage.