PLAAT1 deficiency alleviates high-fat diet-induced hepatic lipid accumulation in mice

The phospholipase A and acyltransferase (PLAAT) family is composed of three isoforms in mice (PLAAT1, 3, and 5), all of which function as phospholipid-metabolizing enzymes exhibiting phospholipase A1 /A2 and acyltransferase activities. Plaat3-deficient (Plaat3-/- ) mice were previously reported to show lean phenotype and remarkable hepatic fat accumulation under high-fat diet (HFD) feeding, while Plaat1-/- mice have not been analyzed. In the present study, we generated Plaat1-/- mice and investigated the effects of PLAAT1 deficiency on HFD-induced obesity, hepatic lipid accumulation, and insulin resistance. After HFD treatment, PLAAT1 deficiency caused a lower body weight gain compared to wild-type mice. Plaat1-/- mice also showed reduced liver weight with negligible hepatic lipid accumulation. In accordance with these findings, PLAAT1 deficiency improved HFD-induced hepatic dysfunction and lipid metabolism disorders. Lipidomics analysis in the liver revealed that in Plaat1-/- mice, the levels of various glycerophospholipids tended to increase, while all classes of lysophospholipids examined tended to decrease, suggesting that PLAAT1 functions as phospholipase A1 /A2 in the liver. Interestingly, the HFD treatment of wild-type mice significantly increased the mRNA level of PLAAT1 in the liver. Furthermore, the deficiency did not appear to elevate the risk of insulin resistance in contrast to PLAAT3 deficiency. These results suggested that the suppression of PLAAT1 improves HFD-induced overweight and concomitant hepatic lipid accumulation.

Transcription factor MafB-mediated inhibition of type I interferons in plasmacytoid dendritic cells

Type I IFNs (IFN-α and IFN-β), immunomodulatory cytokines secreted from activated plasmacytoid dendritic cells (pDCs), contribute to the innate defense against pathogenic infections and the pathogenesis of the autoimmune disease psoriasis vulgaris. A previous study has shown that an E26 transformation-specific (Ets) family transcription factor Spi-B can transactivate the type I IFN promoter in synergy with IFN regulatory factor (IRF)-7 and is required for type I IFN production in pDCs. However, the mechanism of negative regulation of type I IFNs by pDCs remains unknown. In this study, we report that a basic leucine zipper (bZip) transcription factor v-maf musculoaponeurotic fibrosarcoma oncogene homolog B (MafB) suppresses the induction of type I IFNs in pDCs. The elevated expression of MafB inhibited the transactivation of type I IFN genes in a dose-dependent manner. At the molecular level, MafB interacted with the Ets domain of Spi-B and interfered with IRF-7-Spi-B complexation. Decreased MafB mRNA expression and degradation of MafB protein in the early phase of immune responses led to the enhancement of type I IFNs in pDCs. In vivo studies indicated that MafB is involved in resistance against imiquimod-induced psoriasis-like skin inflammation. Overall, these findings demonstrate that MafB acts as a negative regulator of type I IFN induction in pDCs and plays an important role in maintaining immune homeostasis.

Galectin-9 deficiency exacerbates lipopolysaccharide-induced hypothermia and kidney injury

BACKGROUND

Galectin-9 (Gal-9) is a multifunctional lectin that moderates inflammation and organ damage. In this study, we tested whether Gal-9 has a protective role in the pathogenesis of endotoxemic acute kidney injury.

METHODS

We examined the levels of Gal-9 in control mice after lipopolysaccharide (LPS) administration. We developed Gal-9 knockout (KO) mice that lack Gal-9 systemically and evaluated the role of Gal-9 in LPS-induced proinflammatory cytokines, vascular permeability, and renal injury.

RESULTS

Gal-9 levels were increased in the plasma, kidney, and spleen within 4 h after LPS administration to wild-type mice. Gal-9 deficiency did not affect the LPS-induced increase in plasma tumor necrosis factor-α levels at 1 h or vascular permeability at 6 h. Lower urine volume and reduced creatinine clearance were observed in Gal-9-KO mice compared with wild-type mice after LPS administration. Gal-9-KO mice had limited improvement in urine volume after fluid resuscitation compared with wild-type mice. LPS reduced the body temperature 12 h after its administration. Hypothermia had disappeared in wild-type mice by 24 h, whereas it was sustained until 24 h in Gal-9-KO mice. Importantly, maintaining body temperature in Gal-9-KO mice improved the response of urine flow to fluid resuscitation.

CONCLUSION

Deficiency in Gal-9 worsened LPS-induced hypothermia and kidney injury in mice. The accelerated hypothermia induced by Gal-9 deficiency contributed to the blunted response to fluid resuscitation.

Metabolic adaptation to glycolysis is a basic defense mechanism of macrophages for Mycobacterium tuberculosis infection

Macrophages are major components of tuberculosis (TB) granulomas and are responsible for host defenses against the intracellular pathogen, Mycobacterium tuberculosis. We herein showed the strong expression of hypoxia-inducible factor-1α (HIF-1α) in TB granulomas and more rapid death of HIF-1α-conditional knockout mice than wild-type (WT) mice after M. tuberculosis infection. Although interferon-γ (IFN-γ) is a critical host-protective cytokine against intracellular pathogens, HIF-1-deficient macrophages permitted M. tuberculosis growth even after activation with IFN-γ. These results prompted us to investigate the role of HIF-1α in host defenses against infection. We found that the expression of lactate dehydrogenase-A (LDH-A) was controlled by HIF-1α in M. tuberculosis-infected macrophages IFN-γ independently. LDH-A is an enzyme that converts pyruvate to lactate and we found that the intracellular level of pyruvate in HIF-1α-deficient bone marrow-derived macrophages (BMDMs) was significantly higher than in WT BMDMs. Intracellular bacillus replication was enhanced by an increase in intracellular pyruvate concentrations, which were decreased by LDH-A. Mycobacteria in phagosomes took up exogenous pyruvate more efficiently than glucose, and used it as the feasible carbon source for intracellular growth. These results demonstrate that HIF-1α prevents the hijacking of pyruvate in macrophages, making it a fundamental host-protective mechanism against M. tuberculosis.

The mechanism of action of Spi-B in the transcriptional activation of the interferon-α4 gene

Plasmacytoid dendritic cells (pDCs) are characterized by an exclusive expression of nucleic acid sensing Toll-like receptor 7 (TLR7) and TLR9, and production of high amounts of type I interferon (IFN) in response to TLR7/9 signaling. This function is crucial for both antiviral immunity and the pathogenesis of autoimmune diseases. An Ets family transcription factor, i.e., Spi-B (which is highly expressed in pDCs) is required for TLR7/9 signal-induced type I IFN production and can transactivate IFN-α promoter in synergy with IFN regulatory factor-7 (IRF-7). Herein, we analyzed how Spi-B contributes to the transactivation of the Ifna4 promoter. We performed deletion and/or mutational analyses of the Ifna4 promoter and an electrophoretic mobility shift assay (EMSA) and observed an Spi-B binding site in close proximity to the IRF-7 binding site. The EMSA results also showed that the binding of Spi-B to the double-stranded DNA probe potentiated the recruitment of IRF-7 to its binding site. We also observed that the association of Spi-B with transcriptional coactivator p300 was required for the Spi-B-induced synergistic enhancement of the Ifna4 promoter activity by Spi-B. These results clarify the molecular mechanism of action of Spi-B in the transcriptional activation of the Ifna4 promoter.

Syndecans promote mycobacterial internalization by lung epithelial cells

Pulmonary tuberculosis (TB) is an airborne disease caused by the intracellular bacterial pathogen Mycobacterium tuberculosis (Mtb). Alveolar epithelial cells and macrophages are the first point of contact for Mtb in the respiratory tract. However, the mechanisms of mycobacterial attachment to, and internalization by, nonprofessional phagocytes, such as epithelial cells, remain incompletely understood. We identified syndecan 4 (Sdc4) as mycobacterial attachment receptor on alveolar epithelial cells. Sdc4 mRNA expression was increased in human and mouse alveolar epithelial cells after mycobacterial infection. Sdc4 knockdown in alveolar epithelial cells or blocking with anti-Sdc4 antibody reduced mycobacterial attachment and internalization. At the molecular level, interactions between epithelial cells and mycobacteria involved host Sdc and the mycobacterial heparin-binding hemagglutinin adhesin. In vivo, Sdc1/Sdc4 double-knockout mice were more resistant to Mtb colonization of the lung. Our work reveals a role for distinct Sdcs in promoting mycobacterial entry into alveolar epithelial cells with impact on outcome of TB disease.

The Recombinant BCG ΔureC::hly Vaccine Targets the AIM2 Inflammasome to Induce Autophagy and Inflammation

BACKGROUND

The recombinant BCG ΔureC::hly (rBCG) vaccine candidate induces improved protection against tuberculosis over parental BCG (pBCG) in preclinical studies and has successfully completed a phase 2a clinical trial. However, the mechanisms responsible for the superior vaccine efficacy of rBCG are still incompletely understood. Here, we investigated the underlying biological mechanisms elicited by the rBCG vaccine candidate relevant to its protective efficacy.

METHODS

THP-1 macrophages were infected with pBCG or rBCG, and inflammasome activation and autophagy were evaluated. In addition, mice were vaccinated with pBCG or rBCG, and gene expression in the draining lymph nodes was analyzed by microarray at day 1 after vaccination.

RESULTS

BCG-derived DNA was detected in the cytosol of rBCG-infected macrophages. rBCG infection was associated with enhanced absent in melanoma 2 (AIM2) inflammasome activation, increased activation of caspases and production of interleukin (IL)-1β and IL-18, as well as induction of AIM2-dependent and stimulator of interferon genes (STING)-dependent autophagy. Similarly, mice vaccinated with rBCG showed early increased expression of Il-1β, Il-18, and Tmem173 (transmembrane protein 173; also known as STING).

CONCLUSIONS

rBCG stimulates AIM2 inflammasome activation and autophagy, suggesting that these cell-autonomous functions should be exploited for improved vaccine design.

CREBH determines the severity of sulpyrine-induced fatal shock

Although the pyrazolone derivative sulpyrine is widely used as an antipyretic analgesic drug, side effects, including fatal shock, have been reported. However, the molecular mechanism underlying such a severe side effect is largely unclear. Here, we report that the transcription factor CREBH that is highly expressed in the liver plays an important role in fatal shock induced by sulpyrine in mice. CREBH-deficient mice were resistant to experimental fatal sulpyrine shock. We found that sulpyrine-induced expression of cytochrome P450 2B (CYP2B) family genes, which are involved in sulpyrine metabolism, in the liver was severely impaired in CREBH-deficient mice. Moreover, introduction of CYP2B in CREBH-deficient liver restored susceptibility to sulpyrine. Furthermore, ectopic expression of CREBH up-regulated CYP2B10 promoter activity, and in vivo knockdown of CREBH in wild-type mice conferred a significant resistance to fatal sulpyrine shock. These data demonstrate that CREBH is a positive regulator of CYP2B in response to sulpyrine administration, which possibly results in fatal shock.

Ecto-nucleoside triphosphate diphosphohydrolase 7 controls Th17 cell responses through regulation of luminal ATP in the small intestine

Extracellular ATP is released from live cells in controlled conditions, as well as dying cells in inflammatory conditions, and, thereby, regulates T cell responses, including Th17 cell induction. The level of extracellular ATP is closely regulated by ATP hydrolyzing enzymes, such as ecto-nucleoside triphosphate diphosphohydrolases (ENTPDases). ENTPDase1/CD39, which is expressed in immune cells, was shown to regulate immune responses by downregulating the ATP level. In this study, we analyzed the immunomodulatory function of ENTPDase7, which is preferentially expressed in epithelial cells in the small intestine. The targeted deletion of Entpd7 encoding ENTPDase7 in mice resulted in increased ATP levels in the small intestinal lumen. The number of Th17 cells was selectively increased in the small intestinal lamina propria in Entpd7(-/-) mice. Th17 cells were decreased by oral administration of antibiotics or the ATP antagonist in Entpd7(-/-) mice, indicating that commensal microbiota-dependent ATP release mediates the enhanced Th17 cell development in the small intestinal lamina propria of Entpd7(-/-) mice. In accordance with the increased number of small intestinal Th17 cells, Entpd7(-/-) mice were resistant to oral infection with Citrobacter rodentium. Entpd7(-/-) mice suffered from severe experimental autoimmune encephalomyelitis, which was associated with increased numbers of CD4(+) T cells producing both IL-17 and IFN-γ. Taken together, these findings demonstrate that ENTPDase7 controls the luminal ATP level and, thereby, regulates Th17 cell development in the small intestine.

A cluster of interferon-γ-inducible p65 GTPases plays a critical role in host defense against Toxoplasma gondii

Interferon-γ (IFN-γ) is essential for host defense against intracellular pathogens. Stimulation of innate immune cells by IFN-γ upregulates ∼2,000 effector genes such as immunity-related GTPases including p65 guanylate-binding protein (Gbp) family genes. We show that a cluster of Gbp genes was required for host cellular immunity against the intracellular parasite Toxoplasma gondii. We generated mice deficient for all six Gbp genes located on chromosome 3 (Gbp(chr3)) by targeted chromosome engineering. Mice lacking Gbp(chr3) were highly susceptible to T. gondii infection, resulting in increased parasite burden in immune organs. Furthermore, Gbp(chr3)-deleted macrophages were defective in IFN-γ-mediated suppression of T. gondii intracellular growth and recruitment of IFN-γ-inducible p47 GTPase Irgb6 to the parasitophorous vacuole. In addition, some members of Gbp(chr3) restored the protective response against T. gondii in Gbp(chr3)-deleted cells. Our results suggest that Gbp(chr3) play a pivotal role in anti-T. gondii host defense by controlling IFN-γ-mediated Irgb6-dependent cellular innate immunity.

Tetraspanin CD151 protects against pulmonary fibrosis by maintaining epithelial integrity

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a chronic pulmonary disorder of unknown etiology with few treatment options. Although tetraspanins are involved in various diseases, their roles in fibrosis have not been determined.

OBJECTIVES

To investigate the role of tetraspanin CD151 in pulmonary fibrosis.

METHODS

CD151 knockout (KO) mice were studied by histological, biochemical, and physiological analyses and compared with wild-type mice and CD9 KO mice. Further mechanistic analyses were performed in vitro, in vivo, and on samples from patients with IPF.

MEASUREMENTS AND MAIN RESULTS

A microarray study identified an enrichment of genes involved in connective tissue disorders in the lungs of CD151 KO mice, but not in CD9 KO mice. Consistent with this, CD151 KO mice spontaneously exhibited age-related pulmonary fibrosis. Deletion of CD151 did not affect pulmonary fibroblast functions but instead degraded epithelial integrity via attenuated adhesion strength on the basement membrane; CD151-deleted alveolar epithelial cells exhibited increased α-SMA expression with activation of p-Smad2, leading to fibrotic changes in the lungs. This loss of epithelial integrity in CD151 KO lungs was further exacerbated by intratracheal bleomycin exposure, resulting in severe fibrosis with increased mortality. We also observed decreased numbers of CD151-positive alveolar epithelial cells in patients with IPF.

CONCLUSIONS

CD151 is essential for normal function of alveolar epithelial cells; loss of CD151 causes pulmonary fibrosis as a result of epithelial disintegrity. Given that CD151 may protect against fibrosis, this protein represents a novel target for the treatment of fibrotic diseases.

ATF6beta is a host cellular target of the Toxoplasma gondii virulence factor ROP18

Toxoplasma virulence factor ROP18 targets endoplasmic reticulum–bound transcription factor ATF6β in the host cell, leading to the detrimental loss of ATF6β through proteasome-dependent degradation.

The ROP18 kinase has been identified as a key virulence determinant conferring a high mortality phenotype characteristic of type I Toxoplasma gondii strains. This major effector molecule is secreted by the rhoptries into the host cells during invasion; however, the molecular mechanisms by which this kinase exerts its pathogenic action remain poorly understood. In this study, we show that ROP18 targets the host endoplasmic reticulum–bound transcription factor ATF6β. Disruption of the ROP18 gene severely impairs acute toxoplasmosis by the type I RH strain. Because another virulence factor ROP16 kinase modulates immune responses through its N-terminal portion, we focus on the role of the N terminus of ROP18 in the subversion of host cellular functions. The N-terminal extension of ROP18 contributes to ATF6β-dependent pathogenicity by interacting with ATF6β and destabilizing it. The kinase activity of ROP18 is essential for proteasome-dependent degradation of ATF6β and for parasite virulence. Consistent with a key role for ATF6β in resistance against this intracellular pathogen, ATF6β-deficient mice exhibit a high susceptibility to infection by ROP18-deficient parasites. The results reveal that interference with ATF6β-dependent immune responses is a novel pathogenic mechanism induced by ROP18.

A novel in vivo inducible dendritic cell ablation model in mice

Dendritic cells (DCs) are involved in T cell activation via their uptake and presentation of antigens. In vivo function of DCs was analyzed using transgenic mouse models that express diphtheria toxin receptor (DTR) or the diphtheria toxin-A subunit (DTA) under the control of the CD11c/Itgax promoter. However, CD11c+ cells are heterogeneous populations that contain several DC subsets. Thus, the in vivo function of each subset of DCs remains to be elucidated. Here, we describe a new inducible DC ablation model, in which DTR expression is induced under the CD11c/Itgax promoter after Cre-mediated excision of a stop cassette (CD11c-iDTR). Crossing of CD11c-iDTR mice with CAG-Cre transgenic mice, expressing Cre recombinase under control of the cytomegalovirus immediate early enhancer-chicken beta-actin hybrid promoter, led to the generation of mice, in which DTR was selectively expressed in CD11c+ cells (iDTRDelta mice). We successfully deleted CD11c+ cells in bone marrow-derived DCs in vitro and splenic CD11c+ cells in vivo after DT treatment in iDTRDelta mice. This mouse strain will be a useful tool for generating mice lacking a specific subset of DCs using a transgenic mouse strain, in which the Cre gene is expressed by a DC subset-specific promoter.

[Potential of novel antimycobacterial immune factors, SLPI and lipocalin 2]

Mycobacterium tuberculosis, causing tuberculosis, is the pathogen that invades immune cells, especially macrophages, and evade from the host immune response. Recent studies have reported that M. tuberculosis also invade alveolar epithelial cells as well as alveolar macrophages. However, the role of alveolar epithelial cells in the host defense against M. tuberculosis remains unknown. In this study, we demonstrate that secretory leukocyte protease inhibitor (SLPI) and lipocalin 2 are secreted into the alveolar space by alveolar macrophages and epithelial cells during the early phase of respiratory mycobacterial infection. SLPI kills mycobacteria by enhancing the membrane permeability, and lipocalin 2 is internalized into the alveolar epithelial cells and inhibits intracellular mycobacterial growth by blocking iron uptake. Taken together, these findings highlight a pivotal role for alveolar epithelial cells during mycobacterial infection.

A single polymorphic amino acid on Toxoplasma gondii kinase ROP16 determines the direct and strain-specific activation of Stat3

Infection by Toxoplasma gondii down-regulates the host innate immune responses, such as proinflammatory cytokine production, in a Stat3-dependent manner. A forward genetic approach recently demonstrated that the type II strain fails to suppress immune responses because of a potential defect in a highly polymorphic parasite-derived kinase, ROP16. We generated ROP16-deficient type I parasites by reverse genetics and found a severe defect in parasite-induced Stat3 activation, culminating in enhanced production of interleukin (IL) 6 and IL-12 p40 in the infected macrophages. Furthermore, overexpression of ROP16 but not ROP18 in mammalian cells resulted in Stat3 phosphorylation and strong activation of Stat3-dependent promoters. In addition, kinase-inactive ROP16 failed to activate Stat3. Comparison of type I and type II ROP16 revealed that a single amino acid substitution in the kinase domain determined the strain difference in terms of Stat3 activation. Moreover, ROP16 bound Stat3 and directly induced phosphorylation of this transcription factor. These results formally establish an essential and direct requirement of ROP16 in parasite-induced Stat3 activation and the significance of a single amino acid replacement in the function of type II ROP16.

Lipocalin 2-dependent inhibition of mycobacterial growth in alveolar epithelium

Mycobacterium tuberculosis invades alveolar epithelial cells as well as macrophages. However, the role of alveolar epithelial cells in the host defense against M. tuberculosis remains unknown. In this study, we report that lipocalin 2 (Lcn2)-dependent inhibition of mycobacterial growth within epithelial cells is required for anti-mycobacterial innate immune responses. Lcn2 is secreted into the alveolar space by alveolar macrophages and epithelial cells during the early phase of respiratory mycobacterial infection. Lcn2 inhibits the in vitro growth of mycobacteria through sequestration of iron uptake. Lcn2-deficient mice are highly susceptible to intratracheal infection with M. tuberculosis. Histological analyses at the early phase of mycobacterial infection in Lcn2-deficient mice reveal increased numbers of mycobacteria in epithelial cell layers, but not in macrophages, in the lungs. Increased intracellular mycobacterial growth is observed in alveolar epithelial cells, but not in alveolar macrophages, from Lcn2-deficient mice. The inhibitory action of Lcn2 is blocked by the addition of endocytosis inhibitors, suggesting that internalization of Lcn2 into the epithelial cells is a prerequisite for the inhibition of intracellular mycobacterial growth. Taken together, these findings highlight a pivotal role for alveolar epithelial cells during mycobacterial infection, in which Lcn2 mediates anti-mycobacterial innate immune responses within the epithelial cells.

Myxococcus xanthus twin-arginine translocation system is important for growth and development

The twin-arginine translocation (Tat) system serves to export fully folded proteins across the cytoplasmic membrane. In many bacteria, three major components, TatA, TatB and TatC, are the functionally essential constituents of the Tat system. A Myxococcus xanthus tatB-tatC deletion mutant could aggregate and form mounds, but was unable to form fruiting bodies under nutritionally limiting conditions. When tatB-tatC mutant vegetative cells were cultured with 0.5 M glycerol, the cell morphology changed to spore-like spherical cells, but the spores were not resistant to heat and sonication treatments. In contrast to the wild-type strain, the tatB-tatC mutant also showed a decreased cell growth rate and a lower maximum cell concentration. These results suggest possibility that the Tat system may contribute to export of various important proteins for development and growth for M. xanthus.

Gene expression profiles in Ciona intestinalis tailbud embryos

A set of 3423 expressed sequence tags derived from the Ciona intestinalis tailbud embryos was categorized into 1213 independent clusters. When compared with DNA Data Bank of Japan database, 502 clusters of them showed significant matches to reported proteins with distinct function, whereas 184 lacked sufficient information to be categorized (including reported proteins with undefined function) and 527 had no significant similarities to known proteins. Sequence similarity analyses of the 502 clusters in relation to the biosynthetic function, as well as the structure of the message population at this stage, demonstrated that 390 of them were associated with functions that many kinds of cells use, 85 with cell-cell communication and 27 with transcription factors and other gene regulatory proteins. All of the 1213 clusters were subjected to whole-mount in situ hybridization to analyze the gene expression profiles at this stage. A total of 387 clusters showed expression specific to a certain tissue or organ; 149 showed epidermis-specific expression; 34 were specific to the nervous system; 29 to endoderm; 112 to mesenchyme; 32 to notochord; and 31 to muscle. Many genes were also specifically expressed in multiple tissues. The study also highlighted characteristic gene expression profiles dependent on the tissues. In addition, several genes showed intriguing expression patterns that have not been reported previously; for example, four genes were expressed specifically in the nerve cord cells and one gene was expressed only in the posterior part of muscle cells.

This study provides molecular markers for each of the tissues and/or organs that constitutes the Ciona tailbud embryo. The sequence information will also be used for further genome scientific approach to explore molecular mechanisms involved in the formation of one of the most primitive chordate body plans.

Cross-phylum regulatory potential of the ascidian Otx gene in brain development in Drosophila melanogaster

The origin of molecular mechanisms of cephalic development is an intriguing question in evolutionary and developmental biology. Ascidians, positioned near the origin of the phylum Chordata, share a conserved set of anteroposterior patterning genes with vertebrates. Here we report the cross-phylum regulatory potential of the ascidian Otx gene in the development of the Drosophila brain and the head vertex structures. The ascidian Otx gene rescued the embryonic brain defect caused by a null mutation of the Drosophila orthodenticle (otd) gene and enhanced rostral brain development while it suppressed trunk nerve cord formation. Furthermore, the ascidian Otx gene restored the head vertex defects caused by a viable otd mutation, ocelliless, via specific activation and repression of downstream regulatory genes. These cross-phylum regulatory potentials of the ascidian Otx gene are equivalent to the activities of the Drosophila and human otd/Otx genes in these developmental processes. These results support the notion that basal chordates such as ascidians have the same molecular patterning mechanism for the anterior structures found in higher chordates, and suggest a common genetic program of cephalic development in invertebrate, protochordate and vertebrate.

Hremx, the ascidian homologue of ems/emx, is expressed in the anterior and posterior-lateral epidermis but not in the central nervous system during embryogenesis

Recent comparative studies on expression patterns of homeobox genes in the development between ascidians and vertebrates have come to suggest a possibility that a common basic mechanism may exist in the patterning of the central nervous system (CNS). The ems/emx genes have been demonstrated to be involved in the formation and patterning of the anterior CNS in Drosophila and vertebrate embryos. In the present study, we have isolated and analyzed expression of Hremx, the ascidian homologue of ems/emx with particular attention to whether it is expressed in the larval ascidian CNS. Expression of Hremx was detected in the anterior trunk and lateral tail epidermis but not in the anterior CNS. The two expression domains of the epidermis responded in different ways upon treatment with retinoic acid: the anterior expression domain was unaltered, while the posterior expression domain extended to the anterior. The present result suggests that Hremx may have a function in anterior patterning but not in the patterning of the CNS in the ascidian embryo. We suggest the possibility that the function of ems/emx genes in the patterning of the anterior CNS in Drosophila and vertebrate embryos might have been acquired independently in the lineages to Drosophila and vertebrates.

Early expressed genes showing a dichotomous developing pattern in the lancelet embryo

Lancelets (amphioxus), although showing the most similar anatomical features to vertebrates, never develop a vertebrate-like head but rather several structures specific to this animal. The lancelet anatomical specificity seems to be traceable to early developmental stages, such as the vertebrate dorsal and anterior-posterior determinations. The BMP and Wnt proteins play important roles in establishing the early basis of the dorsal structures and the head in vertebrates. The early behavior of BMP and Wnt may be also related to the specific body structures of lancelets. The expression patterns of a dpp-related gene, Bbbmp2/4, and two wnt-related genes, Bbwnt7 and Bbwnt8, have been studied in comparison with those of brachyury and Hnf-3beta class genes. The temporal expression patterns of these genes are similar to those of vertebrates; Bbbmp2/4 and Bbwnt8 are first expressed in the invaginating primitive gut and the equatorial region, respectively, at the initial gastrula stage. However, spatial expression pattern of Bbbmp2/4 differs significantly from the vertebrate cognates. It is expressed in the mid-dorsal inner layer of gastrulae and widely in the anterior region, in which vertebrates block BMP signaling. The present study suggests that the lancelet embryo may have two distinct developmental domains from the gastrula stage, the domains of which coincide later with the lateral diverticular and the somitocoelomic regions. The embryonic origin of the anterior-specific structures in lancelets corresponds to the anterior domain where Bbbmp2/4 is continuously expressed.

Left-right asymmetric expression of BbPtx, a Ptx-related gene, in a lancelet species and the developmental left-sidedness in deuterostomes

The long-standing question of how asymmetric development or asymmetric body structures in lancelets (amphioxus) are phylogenetically related to the body plan of other animals is still untouched. Three anterior structures, the preoral pit, club-shaped gland and mouth, are remarkable asymmetric features in developing lancelets that all open on the left side of the body. A Ptx-related gene, BbPtx is the first identified transcription factor gene with an asymmetrical expression pattern in lancelets similar to that in vertebrates, and thus it may provide a clue for the above question. Expression of the BbPtx gene is first detected at the dorsal margin of the blastopore in early mid-gastrulae and then becomes restricted to the left anterodorsal wall of the primitive gut and to the developing left somitocoelomic system. Expression continues on the left side in the developing preoral pit, club-shaped gland and mouth as well as in the mesoderm at the caudal end. Unlike D-Ptx1 in Drosophila, BbPtx is not coexpressed with a fork head gene in lancelets; instead the two genes are expressed in a complementary fashion on the left side of the embryo. The expression pattern of BbPtx is not compatible with the calcichordate hypothesis of Jefferies, in which the proposed ancestor of chordates rotated its tail 90 degrees counterclockwise in relation to the head/trunk. The expression of both BbPtx and vertebrate Pitx2 in tissues derived from the coelom implies that the left-right asymmetric development has a common origin between cephalochordates and vertebrates. Considering the development of the coelom in deuterostomes, however, left-right asymmetric development involving Pitx2-related genes is rather likely to be a primitive character shared among deuterostomes.

Anteroposterior patterning of the epidermis by inductive influences from the vegetal hemisphere cells in the ascidian embryo

Patterning along the anteroposterior axis is a critical step during animal embryogenesis. Although mechanisms of anteroposterior patterning in the neural tube have been studied in various chordates, little is known about those of the epidermis. To approach this issue, we investigated patterning mechanisms of the epidermis in the ascidian embryo. First we examined expression of homeobox genes (Hrdll-1, Hroth, HrHox-1 and Hrcad) in the epidermis. Hrdll-1 is expressed in the anterior tip of the epidermis that later forms the adhesive papillae, while Hroth is expressed in the anterior part of the trunk epidermis. HrHox-1 and Hrcad are expressed in middle and posterior parts of the epidermis, respectively. These data suggested that the epidermis of the ascidian embryo is patterned anteroposteriorly. In ascidian embryogenesis, the epidermis is exclusively derived from animal hemisphere cells. To investigate regulation of expression of the four homeobox genes in the epidermis by vegetal hemisphere cells, we next performed hemisphere isolation and cell ablation experiments. We showed that removal of the vegetal cells before the late 16-cell stage results in loss of expression of these homeobox genes in the animal hemisphere cells. Expression of Hrdll-1 and Hroth depends on contact with the anterior-vegetal (the A-line) cells, while expression of HrHox-1 and Hrcad requires contact with the posterior-vegetal (the B-line) cells. We also demonstrated that contact with the vegetal cells until the late 32-cell stage is sufficient for animal cells to express Hrdll-1, Hroth and Hrcad, while longer contact is necessary for HrHox-1 expression. Contact with the A-line cells until the late 32-cell stage is also sufficient for formation of the adhesive papillae. Our data indicate that the epidermis of the ascidian embryo is patterned along the anteroposterior axis by multiple inductive influences from the vegetal hemisphere cells and provide the first insight into mechanisms of epidermis patterning in the chordate embryos.

Ascidian tail formation requires caudal function

Although the tail is one of the major characteristics of animals of the phylum Chordata, evolutionary aspects of the molecular mechanisms involved in its formation are not clear. To obtain insights into these issues, we have isolated and investigated the caudal gene of an ascidian, one of the lower animal groups among chordates. Ascidian caudal is expressed from the midgastrula stage onward in the lateral walls of the posterior neural tube cell lineage and also in the posterior epidermal cells from the neurula stage. Thus, ascidian caudal expression is restricted to the ectoderm of a tail-forming region throughout embryogenesis. Suppression of caudal function by an antisense oligonucleotide or a dominant negative construct caused inhibition of the cell movement required for tail formation. Overexpression of wild-type caudal mRNA in an ascidian animal cap, an animal half explant prepared at the eight-cell stage, caused elongation of the cap. Furthermore, Xenopus embryos injected with dominant negative ascidian caudal exhibited defects in elongation, suggesting a conserved caudal function among chordates. These results indicate that caudal function is required for chordate tail formation and may play a key role in its evolution.

Structure and developmental expression of the ascidian TRP gene: insights into the evolution of pigment cell-specific gene expression

The tyrosinase family in vertebrates consists of three related melanogenic enzymes: tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2. These proteins control melanin production in pigment cells and play a crucial role in determining vertebrate coloration. We have isolated a gene from the ascidian Halocynthia roretzi which encodes a tyrosinase-related protein (HrTRP) with 45-49% identity with vertebrate TRP-1 and TRP-2. The expression of the HrTRP gene in pigment lineage a8.25 cells starts at the early-mid gastrula stage, which coincides with the stage when these cells are determined as pigment precursor cells; therefore, it provides the earliest pigment lineage-specific marker, which enables us to trace the complete cell lineage leading to two pigment cells in the larval brain. In addition, the expression pattern of the HrTRP gene appears to share similar characteristics with the mouse TRP-2 gene although structurally the HrTRP gene is more closely related to mammalian TRP-1 genes. Based on these observations and on results from molecular phylogenetic and hybridization analyses, we suggest that triplication of the tyrosinase family occurred during the early radiation of chordates. Initially, duplication of an ancestral tyrosinase gene produced a single TRP gene before the urochordate and cephalochordate-vertebrate divergence, and a subsequent duplication of the ancestral TRP gene in the vertebrate lineage gave rise to two TRP genes before the emergence of teleost fishes. Evolution of the melanin synthetic pathway and possible phylogenetic relationships among chordate pigment cells that accommodate the metabolic process are discussed. Dev Dyn 1999;215:225-237.

Vegetal cell fate specification and anterior neuroectoderm formation by Hroth, the ascidian homologue of orthodenticle/otx

To obtain insights into the mechanisms of gastrulation and neural tube formation, we studied the function and regulation of expression of Hroth, the ascidian homologue of orthodenticle/otx, during embryogenesis. Microinjection of synthetic Hroth mRNA into fertilized eggs led to embryos with an expanded trunk and a reduced tail. In these embryos, development of notochord and muscle was effected. Also, Hroth overexpression caused ectopic formation of anterior neuroectoderm, along with suppression of epidermis development, even in the absence of cell-cell interaction. Furthermore, we demonstrated that ectodermal expression of Hroth requires an inductive influence from the vegetal hemisphere cells. These data suggest roles of Hroth in both specification of mesoendodermal cells and anterior neuroectoderm formation.

Cloning and embryonic expression of Hrsna, a snail family gene of the ascidian Halocynthia roretzi: implication in the origins of mechanisms for mesoderm specification and body axis formation in chordates

snail family genes encode a transcription factor with specific zinc finger motifs. In vertebrates, they are expressed in the entire mesoderm in early embryogenesis and later in the paraxial mesoderm and the tail-bud, suggesting roles in specification and morphogenesis of the paraxial mesoderm. In the present study, a snail family gene Hrsna from a member of the chordates, an ascidian (Halocynthia roretzi), was cloned to obtain an insight into the origin of the mechanisms of mesoderm specification and body axis formation as observed in vertebrates. Expression of Hrsna during ascidian embryogenesis was found to be quite similar to that of vertebrate snail genes. First, before gastrulation, Hrsna was initially expressed in most precursors of mesodermal tissues including the notochord where As-T, the ascidian homolog of brachyury, was expressed. Hrsna expression persisted in the paraxial mesoderm, the mesenchyme and muscle, but not in the notochord precursors. Also, just as vertebrate snail family genes are expressed in the border of the neural plate that develops into dorsal neural tube and neural crest cells, so Hrsna expression was detected in the precursors of lateral and dorsal regions of the neural tube. However, Hrsna expression was not detected in the tip of the tail, unlike in vertebrate counterparts. In the light of the present findings, similarity and dissimilarity of mechanisms governing mesoderm specification and body axis formation between ascidians and vertebrates are discussed.

Opsonic complement component C3 in the solitary ascidian, Halocynthia roretzi

The recent identification of two mannose-binding lectin-associated serine protease clones from Halocynthia roretzi, an ascidian, suggested the presence of a complement system in urochordates. To elucidate the structure and function of this possibly primitive complement system, we have isolated cDNA clones for ascidian C3 (AsC3) and purified AsC3 protein from body fluid. The deduced primary structure of AsC3 shows overall similarity to mammalian C3, including a typical thioester site with the His residue required for nucleophilic activation of the thioester. AsC3 has a two-subunit chain structure, and the alpha-chain is cleaved at a specific site near to the N terminus upon activation. Ascidian body fluid contains an opsonic activity which enhances phagocytosis of yeast by ascidian blood cells, and Ab against AsC3 inhibits this opsonic activity. These results indicate that the complement system played a pivotal role in innate immunity by enhancing phagocytosis before the emergence of the vertebrates and well ahead of the establishment of adaptive immunity, which is believed to have occurred at about the time of the appearance of cartilaginous fish.

Two lineages of mannose-binding lectin-associated serine protease (MASP) in vertebrates

Mannose-binding lectin-associated serine protease (MASP) is a newly identified member of the serine protease superfamily. MASP is involved in host defense against pathogens through a novel system of complement activation, designated the lectin pathway. To elucidate the origin of the lectin pathway and the molecular evolution of MASP, we cloned six MASP cDNAs from five vertebrate species going from mammal to cyclostome. An alignment of the amino acid sequences deduced from the cDNAs revealed the presence of two different lineages of the MASP gene. This classification was supported by the precise correlation with two types of exon organization for the protease domain. One of the two lineages is unique in that a single exon encodes the protease domain, unlike most other serine proteases. All members of this group, termed the AGY type, have an AGY codon at the active site serine. A phylogenetic tree suggests that the AGY type diverged from another lineage, termed the TCN type, before the emergence of primitive vertebrates. Furthermore, the presence of MASP or MASP-like sequences in most vertebrate species suggests that the lectin pathway functions extensively in vertebrates and that its origin is traced back to the invertebrate stage.

Analysis of temporal expression pattern and cis-regulatory sequences of chicken pepsinogen A and C

Three groups of pepsinogens exist in vertebrates, namely, pepsinogen A, pepsinogen C, and prochymosin, which are produced at different developmental stages. In the chicken, prochymosin is expressed only in the embryonic stage, while pepsinogens A and C are secreted from adult chicken proventricular (glandular stomach) mucosa. In order to understand the mechanism of transcriptional regulation of these genes, we have cloned the genes encoding chicken pepsinogens A and C and analyzed the sequences possibly involved in their regulation. 5'-Upstream sequences of both genes contain putative binding motifs for transcription factors such as GATA, Sox, and HNF-3 beta, which are expressed in the chicken gut epithelium. Moreover, we found seven putative binding motifs for human MZF-1 in intron 8 of pepsinogen A gene. These transcription factors may act as regulators of expression of chicken pepsinogen genes.

Retinoic acid affects patterning along the anterior-posterior axis of the ascidian embryo

Because retinoic acid (RA) is known to affect anterior posterior patterning in vertebrate embryos, it was questioned whether it shows similar effects in a more primitive chordate, the ascidian Halocynthia roretzi. Ascidian embryos treated with RA exhibited truncated phenotypes in a dose-dependent manner similar to the anterior truncations seen in vertebrate embryos. The most severely affected larvae possessed a round trunk without the papillae characteristic of the anterior terminal epidermis. Retinoic acid also altered the expression of HrHox-1 and Hroth in a dose-dependent manner. Expression of HrHox-1 increased, whereas expression of Hroth decreased with increasing levels of RA. In treated embryos, HrHox-1 was first expressed pan-ectodermally, then degraded in all but specific regions of the embryo. By contrast, initiation of Hroth expression was not affected, but epidermal expression was lost while expression in the neural tube narrowed toward the anterior in tail-bud embryos. These alterations in the expression of homeobox genes appear to correlate closely to the morphological defects elicited by RA treatment, suggesting broad conservation of developmental patterning mechanisms within the Phylum Chordata.

Tripartite organization of the ancestral chordate brain and the antiquity of placodes: insights from ascidian Pax-2/5/8, Hox and Otx genes

Ascidians and vertebrates belong to the Phylum Chordata and both have dorsal tubular central nervous systems. The structure of the ascidian neural tube is extremely simple, containing less than 400 cells, among which less than 100 cells are neurons. Recent studies suggest that, despite its simple organization, the mechanisms patterning the ascidian neural tube are similar to those of the more complex vertebrate brain. Identification of homologous regions between vertebrate and ascidian nervous systems, however, remains to be resolved. Here we report the expression of HrPax-258 gene: an ascidian homologue of vertebrate Pax-2, Pax-5 and Pax-8 genes. Molecular phylogenetic analyses indicate that HrPax-258 is descendant from a single precursor gene that gave rise to the three vertebrate genes. The expression pattern of HrPax-258 suggests that this subfamily of Pax genes has conserved roles in regional specification of the brain. Comparison with expression of ascidian Otx (Hroth) and a Hox gene (HrHox1) by double-staining in situ hybridizations indicate that the ascidian brain region can be subdivided into three regions; the anterior region marked by Hroth probably homologous to the vertebrate forebrain and midbrain, the middle region marked by HrPax-258 probably homologous to the vertebrate anterior hindbrain (and maybe also midbrain) and the posterior region marked by Hox genes which is homologous to the vertebrate hindbrain and spinal cord. Later expression of HrPax-258 in atrial primordia implies that basal chordates such as ascidians have already acquired a sensory organ that develops from epidermal thickenings (placodes) and expresses HrPax-258; we suggest it is homologous to the vertebrate ear. Therefore, placodes are not likely to be a newly acquired feature in vertebrates, but may have already been possessed by the earliest chordates.

Early specification of intestinal epithelium in the chicken embryo: a study on the localization and regulation of CdxA expression

CdxA, a chicken homeobox-containing gene related to caudal in Drosophila, has been implicated in the regionalization of endoderm. It is reported here that, in the development of the chicken embryo, CdxA expression appears in the endoderm at day 1.5 of development as bilateral bands on either side of the splanchnopleure which later contribute to intestinal epithelium. The CdxA-expressing area extends medially and caudally as formation of the gut tube progresses. It is also shown that the rostral limit of CdxA expression demarcates the boundary between stomach and duodenum after day 3 of development. CdxA is not expressed in digestive tract appendages which open into the intestine, such as pancreas, liver and allantois. Early restriction of CdxA expression in intestinal lineage suggests that the intestinal specification involving CdxA expression commences before the gut tube is formed. The expression of CdxA in epithelial-mesenchymal tissue recombinants suggests that mesenchymal influence regulating CdxA expression plays an important role in confirming the boundary between the stomach and intestine. Chronological change in the spatial distribution of CdxA transcripts and the results of tissue recombination experiments, together with precise fate maps of early endoderm and splanchnic mesoderm, lead to a model of mechanisms by which intestinal specification is brought about.

Hroth an orthodenticle-related homeobox gene of the ascidian, Halocynthia roretzi: its expression and putative roles in the axis formation during embryogenesis

To obtain insight into the axis-forming mechanism in ascidian embryogenesis, Hroth, an ascidian counterpart of orthodenticle/otx, was isolated from Halocynthia roretzi and its expression in embryogenesis was examined by whole mount in situ hybridization. It was revealed that Hroth is expressed in both involuting mesoendoderm and anterior ectoderm during gastrulation while later expression is restricted to the sensory vesicle and anterior epidermis. Expression pattern of Hroth around gastrulation was compared with that of Hrlim, the ascidian LIM class homeobox gene that is known to be expressed during gastrulation. In the light of the present findings on the expression of Hroth, properties of the axis-forming mechanism in ascidian embryogenesis are discussed.

Homeobox genes exhibit evolutionary conserved regionalization in the central nervous system of an ascidian larva

Animals in each subgroup of the phylum Chordata exhibit a similar process by which they form a tubular central nervous system (CNS). However, little is known about spatial relationship among the CNSs of chordates; vertebrates, cephalochordates and urochordates (tunicates). Ascidians constitute a major animal group in the subphylum Urochordata. In the present study, we examined the expression patterns of labial and orthodenticle related genes of the ascidian, Halocynthia roretzi, in the developing larval CNS. These homeobox genes exhibited region-specific expression patterns that are strikingly similar to those of murine Hoxb-1 and Otx2. The regionalization as characterized by the expression of these genes supports the division of the ascidian larval CNS suggested by the previous morphological studies. Furthermore, conservation of the expression pattern of the homeobox genes suggests that such regionalization occurred in the CNS of a putative common ancestor of chordates.

Expression of the labial group Hox gene HrHox-1 and its alteration induced by retinoic acid in development of the ascidian Halocynthia roretzi

Ascidian embryogenesis shares several developmental features with vertebrates. Thus, it is presumed that some molecular mechanisms that are critical for vertebrate development may also act in the early development of ascidians. Here, we investigated expression of the ascidian labial group Hox gene HrHox-1 in the development of Halocynthia roretzi. HrHox-1 showed a spatially restricted expression pattern along the anterior-posterior axis, which is remarkably similar to that of the vertebrate gene, Hoxb-1. The expression of HrHox-1, however, was exclusively in tissues of ectoderm origin unlike its vertebrate counterpart. Exposure of the embryos to 10(−6) M all-trans retinoic acid induced a larval phenotype with elimination of the anteriormost structures, the papillae. In this phenotype, the level of HrHox-1 expression was enhanced and ectopic expression was observed at the anterior terminal epidermis where the papillae are otherwise formed. These observations suggest that there are some conserved mechanisms in the spatial regulation of expression of labial group genes in embryogenesis of ascidians and vertebrates.

Spatially and temporally regulated expression of the LIM class homeobox gene Hrlim suggests multiple distinct functions in development of the ascidian, Halocynthia roretzi

Hrlim is a LIM class homeobox gene that was first isolated from the ascidian Halocynthia roretzi. To assess its roles in early development of the ascidian, spatial and temporal expression of Hrlim was examined by whole mount in situ hybridization. This revealed that transcription of Hrlim is activated at the 32-cell stage specifically in the endoderm lineage. Hrlim is also transiently expressed in all notochord precursor cells. Expression in the endoderm lineage continues through to the middle of gastrulation. After gastrulation, Hrlim is expressed in certain lineages that give rise to subsets of cells in the brain and spinal cord. Based on these observations, it is suggested that Hrlim plays multiple distinct roles in ascidian embryogenesis.

Mesenchymal regulation of epithelial gene expression in developing avian stomach: 5′-flanking region of pepsinogen gene can mediate mesenchymal influence on its expression

The expression of a gene encoding an embryonic chick pepsinogen was investigated in developing avian gut. Expression is restricted to the epithelial layer of the embryonic proventriculus (glandular stomach). We can therefore regard this gene as a marker gene for proventricular epithelial differentiation. There is some considerable evidence in favour of epithelial-mesenchymal interactions being important during the development of the gastrointestinal system; for example, pepsinogen expression is induced in proventricular and gizzard (muscular stomach) epithelial by the proventricular mesenchyme but is suppressed by the gizzard mesenchyme. In the present paper, we studied how the mesenchymes influence this gene expression pattern. For this we produced constructs containing various portions of the 5′-flanking region of the embryonic chick pepsinogen gene, driving reporter sequences (beta-galactocidase or luciferase), and these constructs were transfected into dissociated epithelial cells either from the proventriculus or gizzard. We then recombined these cells with mesenchymal cells and cultured them as cell aggregates. In this way, we were able to dissect the timing and other requirements of the epithelial-mesenchymal interactions for expression of embryonic chick pepsinogen gene. We also report that 1.1 kb of 5′-flanking sequence is sufficient to drive correct expression of embryonic chick pepsinogen gene, although further enhancement was seen if the constructs contained 3.2 kb of upstream sequence.

Developmental changes of DNA methylation pattern of embryonic chick pepsinogen gene

Embryonic chick pepsinogen (ECPg) is one of the pepsinogen isozymogens and its expression is restricted to epithelial cells of the embryonic chick proventriculus (glandular stomach). To examine whether DNA methylation is involved in the regulation of organ-specific and developmental stage-specific expression of ECPg gene, we analyzed the extent of methylation of ECPg gene in normal embryonic and hatched chick organs using methylation-sensitive restriction enzymes. In the proventriculus some CCGG sites underwent demethylation in the gene region after the onset of transcription of the ECPg gene. By contrast, these sites were kept methylated throughout the development in the other organs which do not express ECPg gene. GCGC sites in the gene region became methylated in organs which do not express the ECPg gene, after the initiation of transcription of the ECPg gene in the proventriculus. In the proventriculus, GCGC sites, which were methylated in other organs, were kept unmethylated throughout the development. The methylation state of CpG sites showed no change in the proventriculus of a chick 2 weeks after hatching when the expression of the ECPg gene had completely ceased. The data presented here demonstrate that the DNA methylation is involved in the regulation of organ-specific expression, but stage-specific expression might be brought about by some other mechanisms.

Regulation of androgen receptor by androgen and epidermal growth factor in a human prostatic cancer cell line, LNCaP

The effects of androgen and epidermal growth factor (EGF) on cell proliferation and the expression of mRNA and protein of androgen receptor (AR) were examined in an androgen-sensitive human prostatic cancer cell line, LNCaP, by Northern and Western blot analyses. The addition of 1 nM dihydrotestosterone (DHT), at which the proliferation of the cells was most stimulated, did not change the level of AR mRNA but increased the level of AR protein by reducing the turnover rate of the AR protein. EGF also stimulated the proliferation of the cells but repressed the expression of AR mRNA and protein. This repression was found to be exerted primarily at the level of transcription. When DHT and EGF were added simultaneously to the cells, the level of AR mRNA was reduced to the same degree as was accomplished by the addition of EGF alone. On the other hand, the level of AR protein increased but this increase was about 70% of that attained following the addition of DHT alone. The stimulatory effects of EGF and DHT on cell proliferation were found to be additive. These results indicate that EGF down-regulates the level of AR mRNA and thereby also that of AR protein irrespective of the presence of DHT, and that EGF stimulates the proliferation of LNCaP cells through a different pathway from that of DHT.

Properties of isolated extrachromosomal nucleoli from Tetrahymena pyriformis

Extrachromosomal nucleoli were isolated from log phase cells of Tetrahymena pyriformis (amicronucleate strain) in a highly purified state. Nucleoli located at the periphery of the macronucleus were detached from the nucleoplasmic mass of isolated macronuclei with agitation and separated from macronuclei by filtration through a Nuclepore membrane filter (pore size 5 microm). The filtrate constitutes the crude nucleolar preparation, as judged by electron microscopy and DNA analysis. Further purification of the nucleoli was performed by isopycnic centrifugation of the filtrate in a Metrizamide density gradient. After this step, the purity of the nucleoli, as defined by rDNA content and measured by analytical CsCl centrifugation, was almost 100%. Electron microscopy of the purified nucleoli revealed structures that resemble those of an in situ nucleoli. Undegraded 35S pre-rRNA, together with 26S and 17S rRNA, could be isolated from purified nucleoli. In vitro RNA synthetic activity was associated with isolated nucleoli. This activity is insensitive to low and high concentrations of alpha-amanitin, indicating that the form I RNA polymerase is functioning.

Molecular cloning and expression of a novel homeobox gene AHox1 of the ascidian, Halocynthia roretzi

We have isolated a novel ascidian homeobox gene, designated AHox1, by screening the genomic DNA of Halocynthia roretzi with the Bombyx mori Antennapedia type homeobox as a probe. The AHox1 gene encodes a protein that consists of 741 amino acids. The homeobox of AHox1 is interrupted by 2 introns each of which is about 300 bp in length and it shows about 70% similarity at a deduced amino acid level to that of Drosophila H2.0. This suggests that AHox1 is one of the most diverged homeobox genes so far characterized. Northern blot hybridization with an AHox1 probe showed the presence of single transcripts approximately 2.8 kb in length in larvae, juveniles and some adult tissues. The expression of AHox1 is scarcely detected during the course of early development but it increases to a moderate level at the larval stage. After metamorphosis, the level of AHox1 expression increases as development proceeds. In situ hybridization to the juvenile 7 days after metamorphosis showed that the site of AHox1 expression is the epithelium of digestive tract. Among the adult tissues examined, digestive tract, digestive gland and coelomic cells were the major sites of the expression of AHox1. In gonad, body wall muscle and pharyngeal epithelium, the expression of AHox1 is relatively weak. These results suggest that AHox1 is primarily expressed in the tissues of endodermal origin and that the gene expression may be associated with differentiation of the endodermal tissues.

Long-term follow-up study of children developmentally retarded by early environmental deprivation

In 1972, two children representing a case of severe developmental retardation were discovered and taken into custody. The children, an older sister (referred to as F) and a younger brother (referred to as G), were found to have achieved no more than the physical and mental age level normal to children 1 year of age or less, in spite of their actual respective chronological ages of 6 and 5. Investigation revealed that the children's developmental retardation was due both to extreme social isolation and to complex deprivation. By following their sensorimotor, linguistic, cognitive, and socio-emotional development from the time of discovery to the date of this writing, we have found that their physical and motor development or recovery has proceeded smoothly, whereas their linguistic and cognitive development has continued to show such weaknesses as defective functioning of internal speech (Vygotsky, 1962) and poor ability to deal with abstract, linguistic subjects. F and G have continued to exhibit a tendency toward undersocialization, but this has at times been rather a positive factor in the process of attaining ego identity during adolescence, especially for G, serving to protect him from unreasonable social pressures to conform to group behavior. In combination with other cases of severe deprivation, the case of F and G holds some interesting implications for theories of human development, particularly the notion of critical periods.

Nuclear localization of a DNA-binding C-terminal domain from Balbiani ring coded secretory protein

All known Balbiani ring (BR) genes in Chironomus tentans, coding for giant secretory proteins, the sp-I family, end with a short (110 codons) 3'-end exon which is highly conserved in evolution and is structurally unrelated to the sequences characterizing the core of these proteins. We find that the expressed product, the C-terminal domain, shows sequence-specific DNA binding and that it is likely to be absent in one of the sp-I components, sp-Ib, believed to be coded by the BR2.2 gene. Immunohistochemistry shows that material with reactivity towards antibody against the C-terminal domain is present in the nuclei, and specifically enriched in Balbiani ring 1 and 2. Western blotting of extracts from isolated nuclei demonstrates a component with the same antibody reactivity and of an apparent size somewhat larger than that of the domain. The possibility is discussed that the C-terminal part, which is part of the secretion when derived from some of the BR genes, might be cleaved off and function as a feedback signal to control BR gene activity when derived from the BR2.2 gene.

Subrepeats within the BR1 beta repeat unit in Chironomus pallidivittatus can be classified into different types depending on codon usage

A new type of repeat unit was isolated from Balbiani ring 1 of Chironomus pallidivittatus and designated BR1 beta repeat. It consists of a constant and a subrepeated part, like previously described units belonging to the core blocks of the BR genes. The subrepeated part contains 10-codon subrepeats with an arrangement similar to the subrepeats of the previously described BR2 beta gene. The present unit differs from earlier reported core units firstly in a much lower number of copies (about 15) per genome, which are tandemly arranged. Secondly, the number of subrepeats per BR1 beta repeat unit can show great variations. On the basis of the pattern of codon usage, three types of subrepeats can be distinguished. One type lies 5'-proximal in the subrepeat array and consists of variable numbers of subrepeats almost identical at the nucleotide level. The last complete subrepeat represents another type, with consistent differences in codon usage as compared to subrepeats of the proximal type. Finally, there is an intermediate type represented by the subrepeat preceding the distal one. Here, codon characteristics from proximal and distal subrepeats are mixed in a patchy and irregular way. The evolution of the arrays can be understood either as being the result of subrepeat formation in two steps (occurring before and after amplification of whole repeat units) or as the result of a continuous process in which there is evidence for participation of gene conversion.