Requirement of tissue-selective TBP-associated factor TAFII105 in ovarian development.

Transcription factor TFIID, composed of TBP and TAFII subunits, is a central component of the RNA polymerase II machinery. Here, we report that the tissue-selective TAFII105 subunit of TFIID is essential for proper development and function of the mouse ovary. Female mice lacking TAFII105 are viable but infertile because of a defect in folliculogenesis correlating with restricted expression of TAFII105 in the granulosa cells of the ovarian follicle. Gene expression profiling has uncovered a defective inhibin-activin signaling pathway in TAFII105-deficient ovaries. Together, these studies suggest that TAFII105 mediates the transcription of a subset of genes required for proper folliculogenesis in the ovary and establishes TAFII105 as a cell type-specific component of the mammalian transcriptional machinery.

Enhancement of CD8+ T cell responses by ICOS/B7h costimulation.

Although the recently identified ICOS/B7h costimulatory counterreceptors are critical regulators of CD4(+) T cell responses, their ability to regulate CD8(+) responses is unclear. Here we report using a tumor-rejection model that ectopic B7h expression can costimulate rejection by CD8(+) T cells in the absence of CD4(+) T cells. Although responses of naive T cells were significantly augmented by priming with B7h, B7h was surprisingly effective in mobilizing recall responses of adoptively transferred T cells. To explore why secondary responses of CD8(+) T cells were particularly enhanced by B7h, kinetics of ICOS up-regulation, proliferative responses, and cytokine production were compared from both naive and rechallenged 2C-transgenic T cells costimulated in vitro. Although B7h costimulated proliferative responses from both CD8(+) populations, rechallenged cells were preferentially costimulated for IL-2 and IFN-gamma production. These results indicate that ICOS/B7h counterreceptors likely function in vivo to enhance secondary responses by CD8(+) T cells.

B7h, a novel costimulatory homolog of B7.1 and B7.2, is induced by TNFalpha.

In a screen to identify genes induced by NF-kappaB/Rel transcription factors, we cloned a novel gene, b7h, that is a close homolog of B7 costimulatory ligands expressed on antigen-presenting cells. B7h can costimulate proliferation of purified T cells through a receptor on T cells distinct from CD28 or CTLA-4. Surprisingly, although B7h is expressed in unstimulated B cells, its expression is induced in both 3T3 cells and embryonic fibroblasts treated with TNFalpha, and it is upregulated in nonlymphoid tissues of mice treated with LPS, a potent activator of TNFalpha. These data define a novel costimulatory ligand for T cells and suggest that induction of B7h by TNFalpha may function as a mechanism to directly augment recognition of self during inflammation.

The Ets transcription factor ERM is Th1-specific and induced by IL-12 through a Stat4-dependent pathway.

Interleukin 12 (IL-12)-induced T helper 1 (Th1) development requires Stat4 activation. However, antigen-activated Th1 cells can produce interferon gamma (IFN-gamma) independently of IL-12 and Stat4 activation. Thus, in differentiated Th1 cells, factors regulated by IL-12 and Stat4 may be involved in IFN-gamma production. Using subtractive cloning, we identified ERM, an Ets transcription factor, to be a Th1-specific, IL-12-induced gene. IL-12-induction of ERM occurred in wild-type and Stat1-deficient, but not Stat4-deficient, T cells, suggesting ERM is Stat4-inducible. Retroviral expression of ERM did not restore IFN-gamma production in Stat4-deficient T cells, but augmented IFN-gamma expression in Stat4-heterozygous T cells. Ets factors frequently regulate transcription via cooperative interactions with other transcription factors, and ERM has been reported to cooperate with c-Jun. However, in the absence of other transcription factors, ERM augmented expression of an IFN-gamma reporter by only 2-fold. Thus, determining the requirement for ERM in Th1 development likely will require gene targeting.

Inhibition of Th1 development mediated by GATA-3 through an IL-4-independent mechanism.

Recently, the transcription factor GATA-3 was shown to be selectively expressed in Th2 but not Th1 cells and to augment Th2-specific cytokines. Here, we show that loss of GATA-3 expression by developing Th1 cells requires IL-12 signaling through Stat4 and does not simply result from an absence of IL-4. Moreover, we demonstrate a novel role for GATA-3 in directly repressing Th1 development distinct from its positive actions on Th2-specific cytokines. GATA-3 inhibits Th1 cytokines by a cell-intrinsic mechanism that is not dependent on IL-4 and that may involve repression of IL-12 signaling. Thus, GATA-3 expression and IL-12 signaling are mutually antagonistic, which facilitates rapid dominance of one pathway during early Th development, producing a stable divergence in cytokine profiles.

GATA-3-dependent enhancer activity in IL-4 gene regulation.

Previously, we analyzed the proximal IL-4 promoter in directing Th2-specific activity. An 800-base pair proximal promoter conferred some Th2-selective expression in transgenic mice. However, this region directed extremely low reporter mRNA levels relative to endogenous IL-4 mRNA, suggesting that full gene activity requires additional enhancer elements. Here, we analyzed large genomic IL-4 regions for enhancer activity and interaction with transcription factors. The proximal IL-4 promoter is only moderately augmented by GATA-3, but certain genomic regions significantly enhanced GATA-3 promoter transactivation. Some enhancing regions contained consensus, GATA sites that bound Th2-specific complexes. However, retroviral transduction of GATA-3 into developing T cells induced IL-5 to full Th2 levels, but only partially restored IL-4 production. Thus, we propose that GATA-3 is permissive, but not sufficient, for full IL-4 enhancement and may act through GATA elements surrounding the IL-13/IL-4 gene locus.

p50-NF-kappaB complexes partially compensate for the absence of RelB: severely increased pathology in p50(-/-)relB(-/-) double-knockout mice.

RelB-deficient mice (relB(-/-)) have a complex phenotype including multiorgan inflammation and hematopoietic abnormalities. To examine whether other NF-kappaB/Rel family members are required for the development of this phenotype or have a compensatory role, we have initiated a program to generate double-mutant mice that are deficient in more than one family member. Here we report the phenotypic changes in relB(-/-) mice that also lack the p50 subunit of NF-kappaB (p50(-/-)). The inflammatory phenotype of p50(-/-)relB(-/-) double-mutant mice was markedly increased in both severity and extent of organ involvement, leading to premature death within three to four weeks after birth. Double-knockout mice also had strongly increased myeloid hyperplasia and thymic atrophy. Moreover, B cell development was impaired and, in contrast to relB(-/-) single knockouts, B cells were absent from inflammatory infiltrates. Both p50(-/-) and heterozygous relB(-/+) animals are disease-free. In the absence of the p50, however, relB(-/+) mice (p50(-/-)relB(-/+)) had a mild inflammatory phenotype and moderate myeloid hyperplasia. Neither elevated mRNA levels of other family members, nor increased kappaB-binding activities of NF-kappaB/Rel complexes could be detected in single- or double-mutant mice compared to control animals. These results indicate that the lack of RelB is, in part, compensated by other p50-containing complexes and that the "classical" p50-RelA-NF-kappaB activity is not required for the development of the inflammatory phenotype.

Both multiorgan inflammation and myeloid hyperplasia in RelB-deficient mice are T cell dependent.

Mice with a targeted disruption of RelB, a member of the Rel/NF-kappaB family of transcription factors, have multifocal, mixed inflammatory cell infiltration in several organs, myeloid hyperplasia, and splenomegaly due to extramedullary hemopoiesis. To elucidate the cellular requirements for this complex phenotype, we have bred RelB-deficient (RelB(kappaO)) animals to two strains of immunodeficient mice, recombinase-activating gene-1-deficient (RAG-1(kappaO), lacking B and T cells), and Nur77/N10-transgenic mice (Nur77/N10(TG), lacking only T cells). We also generated mutant mice deficient in both RelB and the p50 subunit of NF-kappaB (p50(kappaO), multiple defects in B cell function). RelB(kappaO)RAG-1(kappaO) and RelB(kappaO)Nur77/N10(TG) mice are disease-free, while RelB(kappaO)p50(kappaO) double-mutant animals develop an even more severe phenotype despite the absence of B cells in the inflammatory infiltrates. Thus, both multiorgan inflammation and myeloid hyperplasia in RelB-deficient mice are T cell dependent, whereas B cells are not crucially involved.

Regulation of 3' IgH enhancers by a common set of factors, including kappa B-binding proteins.

Targeted disruption of the p50 subunit of NF-kappa B resulted in isotype class switch defects resembling those observed in mice in which the downstream IgH enhancer 3'alpha E(hs1,2) was deleted. We postulated that kappa B binding proteins may regulate class switching by interacting with 3'alpha E(hs1,2) or with other IgH 3' enhancers with which 3'alpha E(hs1,2) synergizes. kappa B binding sites were identified in 3'alpha E(hs1,2) and 3' alpha-hs4, the distal 3' IgH enhancer. A kappa B binding site within 3'alpha E(hs1,2) contributes to at least half the activity of the enhancer in plasma cells, while the same kappa B binding site participates in the complex repression of the enhancer in B cells. In the case of 3'alpha-hs4, a kappa B binding complex activates the enhancer in pre-B, B cells and plasma cells. Additional binding sites within 3'alpha-hs4 for factors known to regulate 3'alpha E(hs1,2), including Oct-1 and BSAP, were identified, and their contribution to 3'alpha-hs4 regulation during B cell development was assessed. Oct-1 positively regulates the enhancer in pre-B and B cells, while BSAP is a repressor in pre-B cells and an activator at the B cell stage. These studies identify kappa B binding proteins as key modulators of 3'alpha E(hs1,2) and 3'alpha-hs4, and suggest coregulation of the two enhancers by a common set of factors.

B cells from p50/NF-kappa B knockout mice have selective defects in proliferation, differentiation, germ-line CH transcription, and Ig class switching.

To better understand the role of NF-kappaB in normal B cell physiology, we used a purified population of resting B cells from p50/NF-kappa B knockout (p50-/-) mice to determine their ability to proliferate, secrete Ig, express germ-line CHRNA, and undergo Ig isotype switching in vitro in response to a number of distinct stimuli. p50-/- B cells proliferated normally in response to dextran-anti-IgD Abs (alpha delta-dex) and membrane-bound, but not soluble, CD40 ligand (CD40), and they were virtually unresponsive to LPS when compared with control B cells. p50-/- B cells secreted markedly reduced Ig in response to alpha delta-dex or mCD40L in the presence of IL-4 + IL-5, despite their relatively normal proliferative rates, whereas normal Ig secretion was restored by the combination of alpha delta-dex and CD40L. p50-/- B cells expressed normal steady-state levels of germ-line CH gamma 1 and CH alpha RNA but markedly reduced germ-line CH gamma 3 and CH epsilon RNA upon appropriate stimulation. Although p50-/- B cells underwent substantial switching to IgG1, a marked reduction in the switch to IgG3 and IgE, as IgA, was observed. These data are the first to demonstrate key, independent roles for p50/NF-kappaB in normal B cell maturation to Ig secretion, germ-line CH gene activation, and Ig class switching, as well as mitogenesis, and provide a powerful and well-defined in vitro model system for studying the role of p50/NF-kappaB in a wide range of normal cellular functions.

Constitutive NF-kappa B activation, enhanced granulopoiesis, and neonatal lethality in I kappa B alpha-deficient mice.

Transcription factors belonging to the NF-kappa B family are controlled by inhibitory I kappa B proteins, mainly I kappa B alpha and I kappa B beta. Apparently normal at birth, I kappa B alpha-/- mice exhibit severe runting, skin defects, and extensive granulopoiesis postnatally, typically dying by 8 days. Hematopoietic tissues from these mice display elevated levels of both nuclear NF-kappa B and mRNAs of some, but not all, genes thought to be regulated by NF-kappa B. NF-kappa B elevation results in these phenotypic abnormalities because mice lacking both I kappa B alpha and the p50 subunit of NF-kappa B show a dramatically delayed onset of abnormalities. In contrast to hematopoietic cells, I kappa B alpha-/- embryonic fibroblasts show minimal constitutive NF-kappa B, as well as normal signal-dependent NF-kappa B activation that is concomitant with I kappa B beta degradation. Our results indicate that I kappa b beta, but not I kappa B alpha, is required for the signal-dependent activation of NF-kappa B in fibroblasts. However, I kappa B alpha is required for the postinduction repression of NF-kappa B in fibroblasts. These results define distinct roles for the two forms of I kappa B and demonstrate the necessity for stringent control of NF-kappa B.

Embryonic lethality and liver degeneration in mice lacking the RelA component of NF-kappa B.

NF-kappa B, which consists of two polypeptides, p50 (M(r) 50K) and p65/RelA (M(r) 65K), is thought to be a key regulator of genes involved in responses to infection, inflammation and stress. Indeed, although developmentally normal, mice deficient in p50 display functional defects in immune responses. Here we describe the generation of mice deficient in the RelA subunit of NF-kappa B. Disruption of the relA locus leads to embryonic lethality at 15-16 days of gestation, concomitant with a massive degeneration of the liver by programmed cell death or apoptosis. Embryonic fibroblasts from RelA-deficient mice are defective in the tumour necrosis factor (TNF)-mediated induction of messenger RNAs for I kappa B alpha and granulocyte/macrophage colony stimulating factor (GM-CSF), although basal levels of these transcripts are unaltered. These results indicate that RelA controls inducible, but not basal, transcription in NF-kappa B-regulated pathways.

Targeted disruption of the p50 subunit of NF-kappa B leads to multifocal defects in immune responses.

NF-kappa B, a heterodimeric transcription factor composed of p50 and p65 subunits, can be activated in many cell types and is thought to regulate a wide variety of genes involved in immune function and development. Mice lacking the p50 subunit of NF-kappa B show no developmental abnormalities, but exhibit multifocal defects in immune responses involving B lymphocytes and nonspecific responses to infection. B cells do not proliferate in response to bacterial lipopolysaccharide and are defective in basal and specific antibody production. Mice lacking p50 are unable effectively to clear L. monocytogenes and are more susceptible to infection with S. pneumoniae, but are more resistant to infection with murine encephalomyocarditis virus. These data support the role of NF-kappa B as a vital transcription factor for both specific and nonspecific immune responses, but do not indicate a developmental role for the factor.

Sequential induction of NF-kappa B/Rel family proteins during B-cell terminal differentiation.

The NF-kappa B/Rel family of at least five transcription factor polypeptides is thought to function both as a developmental regulator in B cells and as a rapid response system in all cells. To examine this notion in more detail, we determined the protein contents of both the inducible and constitutive NF-kappa B/Rel activities in a pre-B-cell line, 70Z/3, and a mature B-cell line, WEHI 231. NF-kappa B p50/p65 is the major inducible nuclear complex after lipopolysaccharide or phorbol myristate acetate treatment of 70Z/3 cells. The constitutive and inducible complexes in WEHI 231 cells are mainly composed of p50 and Rel. The constitutive or induced activities are all sensitive to I kappa B-alpha, but this inhibitor is very short-lived in WEHI 231 cells, suggesting that the balance between synthesis and degradation of I kappa B-alpha determines whether a particular cell lineage has constitutive activity. A patterned expression of the NF-kappa B/Rel activator proteins emerges from an analysis of other B-lineage cell lines and splenic B cells: mainly p50 and p65 in pre-B (and non-B) cells, a predominance of Rel and p50 in mature B cells, and expression of p52 and RelB in plasmacytoma lines. This ordered pattern of regulators may reflect the requirement for expression of different genes during terminal B-cell differentiation because different combinations of NF-kappa B/Rel family members preferentially activate distinct kappa B sites in reporter constructs.

CD8 is needed for positive selection but differentially required for negative selection of T cells during thymic ontogeny.

During thymic development, immature thymocytes expressing major histocompatibility complex (MHC) class I-restricted T cell receptors (TcR) differentiate into CD8+ T cells with cytolytic functions. To evaluate the role of CD8 in positive and negative selection during thymic ontogeny, mice rendered CD8-null by gene targeting were bred with three lines of transgenic mice expressing unique MHC class I-restricted TcR. In all three instances CD8 was required for positive selection of MHC class I-restricted transgenic T cells. The efficiency of positive selection decreased in accordance with a reduced level of CD8 expression on thymocytes. Surprisingly, there was a differential requirement for CD8 expression in negative selection of MHC class I-restricted thymocytes, depending on the antigen specificity of TcR. These observations show that CD8 is essential for positive selection but is differentially required for negative selection of MHC class I-restricted T cells. Thus thymic selection, at least for negative selection, can occur in the absence of the CD8 accessory molecule.

Functional analysis of the murine T-cell receptor beta enhancer and characteristics of its DNA-binding proteins.

The minimal T-cell receptor (TCR) beta-chain (TCR beta) enhancer has been identified by transfection into lymphoid cells. The minimal enhancer was active in T cells and in some B-lineage cells. When a larger fragment containing the minimal enhancer was used, its activity was apparent only in T cells. Studies with phytohemagglutinin and 4 beta-phorbol-12,13-dibutyrate revealed that the enhancer activity was increased by these agents. By a combination of DNase I footprinting, gel mobility shift assay, and methylation interference analysis, seven different motifs were identified within the minimal enhancer. Furthermore, competition experiments showed that some of these elements bound identical or similar factors that are known to bind to the TCR V beta promoter decamer or to the immunoglobulin enhancer kappa E2 or muEBP-E motif. These shared motifs may be important in the differential gene activity among the different lymphoid subsets.

Positive selection of transgenic receptor-bearing thymocytes by Kb antigen is altered by Kb mutations that involve peptide binding.

A specific interaction between the class I major histocompatibility complex molecule Kb and thymocytes expressing the antigen receptor from the cytolytic T lymphocyte 2C enhances maturation of T cells of the CD8 lineage in transgenic mice. By analyzing transgenic mice backcrossed to Kbm mutant strains of mice, we have identified five bm mutations of the Kb antigen-encoding gene that alter the positive selection of thymocytes induced by Kb antigen. Compared with Kb, Kbm10 and Kbm1 did not induce significant maturation of 2C T-cell receptor-bearing thymocytes, and Kbm8 antigen positively selected for transgenic thymocytes only weakly. Altering residue 77 of Kb molecule from aspartic acid to serine made Kbm3 and Kbm11 allogeneic targets for the 2C antigen receptor and caused deletion of transgenic thymocytes. This deletion spared T cells that expressed low levels of CD8, a result differing from the total deletion of CD8-bearing T cells seen in mice that expressed the original target alloantigen Ld. This evidence indicates that (i) self-peptides bound to thymic major histocompatibility complex molecules can influence the positive selection of thymocytes and (ii) thymocytes with apparently weak interaction with self-major histocompatibility complex antigens can escape clonal deletion.

Evidence for CD8-independent T cell maturation in transgenic mice.

Double-negative (CD4-/CD8-) T cells expressing the alpha/beta transgenic TCR from the 2C cell line (anti-H-2Ld) were examined in the periphery of animals whose MHC type produces positive, negative, or no selection for differentiation of the TCR on single positive (CD8+) cells. Regardless of the selection haplotype the CD4-/CD8- cells are capable of activation by anticlonotypic mAb indicating that negative selection does not inactivate the "forbidden" TCR. Rather, the lack of response to H-2Ld in the negative haplotype is likely to absence of CD8 required to produce a functional response to H-2Ld. The similarity of surface phenotype and functional activity of these CD4-/CD8- cells maturing in different haplotypes suggests they may arise by an alternative lineage which, unlike the dominant TCR alpha/beta pathway, does not require coexpression of CD4/CD8.