5-HT7R enhances neuroimmune resilience and alleviates meningitis by promoting CCR5 ubiquitination

INTRODUCTION

Excessive immune activation induces tissue damage during infection. Compared to external strategies to reconstruct immune homeostasis, host balancing ways remain largely unclear.

OBJECTIVES

Here we found a neuroimmune way that prevents infection-induced tissue damage.

METHODS

By FACS and histopathology analysis of brain Streptococcus pneumonia meningitis infection model and behavioral testing. Western blot, co-immunoprecipitation, and ubiquitination analyze the Fluoxetine initiate 5-HT7R-STUB1-CCR5 K48-linked ubiquitination degradation.

RESULTS

Fluoxetine, a selective serotonin reuptake inhibitor, or the agonist of serotonin receptor 5-HT7R, protects mice from meningitis by inhibiting CCR5-mediated excessive immune response and tissue damage. Mechanistically, the Fluoxetine-5-HT7R axis induces proteasome-dependent degradation of CCR5 via mTOR signaling, and then recruits STUB1, an E3 ubiquitin ligase, to initiate K48-linked polyubiquitination of CCR5 at K138 and K322, promotes its proteasomal degradation. STUB1 deficiency blocks 5-HT7R-mediated CCR5 degradation.

CONCLUSION

Our results reveal a neuroimmune pathway that balances anti-infection immunity via happiness neurotransmitter receptor and suggest the 5-HT7R-CCR5 axis as a potential target to promote neuroimmune resilience.

Negative Regulation of RIG-I by Tim-3 Promotes H1N1 Infection

The mechanisms by which retinoic acid-inducible gene I (RIG-I), a critical RNA virus sensor, is regulated in many biological and pathological processes remain to be determined. Here, we demonstrate that T cell immunoglobulin and mucin protein-3 (Tim-3), an immune checkpoint inhibitor, mediates infection tolerance by suppressing RIG-I-type I interferon pathway. Overexpression or blockade of Tim-3 affects type I interferon expression, virus replication, and tissue damage in mice following H1N1 infection. Tim-3 signaling decreases RIG-I transcription via STAT1 in macrophages and promotes the proteasomal dependent degradation of RIG-I by enhancing K-48-linked ubiquitination via the E3 ligase RNF-122. Silencing RIG-I reversed Tim-3 blockage-mediated upregulation of type I interferon in macrophages. We thus identified a new mechanism through which Tim-3 mediates the immune evasion of H1N1, which may have clinical implications for the treatment of viral diseases.

Screening, identification, purification and homologous modeling of marine cold-active alpha-amylase

BACKGROUND

Cold-active α-amylase is essential in industrial production. However, the number of cold-active α-amylases available for use is limited. Screening microbial strains would lay the groundwork for the future development of the food and pharmaceutical industries.

OBJECTIVE

To screen microbial strains for cold-active α-amylase based on physiological and biochemical identification, as well as homology modelling.

MATERIALS AND METHODS

Cold-active α-amylase strains were screened from water and mud obtained from the Yellow Sea. Colony morphology, Gram staining, scanning electron microscopy and transmission electron microscopy, physiological and biochemical identification and 16S rRNA gene analysis were used to identify strains. A series of steps, including DEAE-anion exchange column chromatography, SephadexG-100 column chromatography, and SDS-PAGE electrophoresis, were used to produce cold-active α-amylase of relatively high purity. Finally, the homology of amylase was modeled to explore the structure and activity site of the enzyme.

RESULTS

The named dsh19-1 strain of cold-active α-amylase was screened and identified as Bacillus. The cold-active α-amylase produced by Bacillus was named AmyD-1. The protein with PDB sequence number 5A2B was found to have 40.6% homology with AmyD-1. The verification score of the 3-D model was 137.07 points. We discovered that the six sites are potential sites for amylase to decompose starch by building a 3-D AmyD-1 model. AmyD-1 has a molecular weight of 1515 bp, and hydrogen bonding may be the primary interaction force between AmyD-1 and glucose molecules.

CONCLUSION

A cold-active α-amylase produced by Bacillus strain dsh19-1 was successfully obtained and named AmyD-1. This enzyme has potential uses in the food and pharmaceutical industries.

[Interference of long noncoding RNA FOXCUT inhibits epithelial-mesenchymal transformation and induces mitochondrial injury in nasopharyngeal carcinoma cells]

OBJECTIVE

To investigate the effects of RNA interference of long noncoding RNA FOXCUT on epithelial mesenchymal transformation and mitochondrial function in nasopharyngeal carcinoma (NPC) cells.

METHODS

FOXCUT expression levels were detected by RT-PCR in tumor tissues and adjacent tissues from 50 patients with NPC and in NP69, CNE1, CNE2, SUNE2, HER2 and 5-8F cell lines. CNE1 cells were transfected with a short hairpin RNA (shRNA) targeting FOXCUT or a negative control RNA construct (shRNA-NC), and the changes in cell proliferation and morphology were assessed with CCK8 assay, clone formation assay and microscopic observation. An immunofluorescence assay was used to examine the vimentin-positive cells, and the levels of SOD, MDA and LDH in the cells were detected. The changes of mitochondrial membrane potential were detected with flow cytometry, and the expression levels of E-cad, N-cad, vimentin, Bax, Bcl-2, caspase-3 and c-Myc in the cells were detected with Western blotting.

RESULTS

The expression level of FOXCUT was significantly increased in NPC tissues as compared with the adjacent tissues (P < 0.001). Compared with NP69 cells, CNE1, CNE2, SUNE2, HER2 and 5-8F cells all exhibited significantly increased expressions of FOXCUT (P < 0.001). In CNE1 cells, transfection with FOXCUT shRNA significantly inhibited cell proliferation and clone formation (P < 0.001), and caused obvious changes in cell morphology. FOXCUT knockdown significantly decreased the expressions of N-cad and vimentin, increased E- cad expression and the contents of MDA and LDH (P < 0.05), reduced vimentin- positive cells and the activity of SOD, and caused a shift of red fluorescent cells to green fluorescent cells and an increased percentage of green fluorescent cells. FOXCUT knockdown also resulted in significantly increased expressions of Bax/Bcl2 and cleaved Cas3/Cas3 and a lowered expression of c-Myc.

CONCLUSIONS

Interference of FOXCUT can inhibit the proliferation and epithelial-mesenchymal transformation, enhance oxidative stress, induce mitochondrial function injury, and promote apoptosis in NPC cells, suggesting the potential of FOXCUT interference for targeted treatment of NPC.

Ubiquitination and degradation of NF90 by Tim-3 inhibits antiviral innate immunity

Nuclear factor 90 (NF90) is a novel virus sensor that serves to initiate antiviral innate immunity by triggering stress granule (SG) formation. However, the regulation of the NF90-SG pathway remains largely unclear. We found that Tim-3, an immune checkpoint inhibitor, promotes the ubiquitination and degradation of NF90 and inhibits NF90-SG-mediated antiviral immunity. Vesicular stomatitis virus (VSV) infection induces the up-regulation and activation of Tim-3 in macrophages, which in turn recruit the E3 ubiquitin ligase TRIM47 to the zinc finger domain of NF90 and initiate a proteasome-dependent degradation via K48-linked ubiquitination at Lys297. Targeted inactivation of Tim-3 enhances the NF90 downstream SG formation by selectively increasing the phosphorylation of protein kinase R and eukaryotic translation initiation factor 2α, the expression of SG markers G3BP1 and TIA-1, and protecting mice from VSV challenge. These findings provide insights into the crosstalk between Tim-3 and other receptors in antiviral innate immunity and its related clinical significance.

Peripheral Injection of Tim-3 Antibody Attenuates VSV Encephalitis by Enhancing MHC-I Presentation

Viral encephalitis is the most common cause of encephalitis. It is responsible for high morbidity rates, permanent neurological sequelae, and even high mortality rates. The host immune response plays a critical role in preventing or clearing invading pathogens, especially when effective antiviral treatment is lacking. However, due to blockade of the blood-brain barrier, it remains unclear how peripheral immune cells contribute to the fight against intracerebral viruses. Here, we report that peripheral injection of an antibody against human Tim-3, an immune checkpoint inhibitor widely expressed on immune cells, markedly attenuated vesicular stomatitis virus (VSV) encephalitis, marked by decreased mortality and improved neuroethology in mice. Peripheral injection of Tim-3 antibody enhanced the recruitment of immune cells to the brain, increased the expression of major histocompatibility complex-I (MHC-I) on macrophages, and as a result, promoted the activation of VSV-specific CD8⁺ T cells. Depletion of macrophages abolished the peripheral injection-mediated protection against VSV encephalitis. Notably, for the first time, we found a novel post-translational modification of MHC-I by Tim-3, wherein, by enhancing the expression of MARCH9, Tim-3 promoted the proteasome-dependent degradation of MHC-I via K48-linked ubiquitination in macrophages. These results provide insights into the immune response against intracranial infections; thus, manipulating the peripheral immune cells with Tim-3 antibody to fight viruses in the brain may have potential applications for combating viral encephalitis.

Tim-3 Promotes Listeria monocytogenes Immune Evasion by Suppressing Major Histocompatibility Complex Class I

BACKGROUND

T-cell immunoglobulin and mucin protein 3 (Tim-3) is an immune checkpoint inhibitor that has therapeutic implications for many tumors and infectious diseases. However, the mechanisms by which Tim-3 promotes immune evasion remain unclear.

METHODS

In this study, we demonstrated that Tim-3 inhibits the expression of major histocompatibility complex class I (MHC-I) in macrophages at both the messenger ribonucleic acid and protein levels by inhibiting the STAT1-NLRC5 signaling pathway.

RESULTS

As a result, MHC-I-restricted antigen presentation by macrophages was inhibited by Tim-3 both in vitro and in a Listeria monocytogenes infection model in vivo. Systemic overexpression of Tim-3 or specific knockout of Tim-3 in macrophages significantly attenuated or enhanced CD8+ T-cell activation and infection damage in L monocytogenes-infected mice, respectively.

CONCLUSIONS

Thus, we identified a new mechanism by which Tim-3 promotes L monocytogenes immune evasion. Further studies on this pathway might shed new light on the physio-pathological roles of Tim-3 and suggest new approaches for intervention.

T cell immunoglobulin and mucin domain protein 3 inhibits glycolysis in RAW 264.7 macrophages through Hexokinase 2

T cell immunoglobulin and mucin domain-3 (Tim-3), an immune checkpoint molecule, plays critical roles in maintaining innate immune homeostasis; however, the mechanisms underlying these roles remain to be determined. Here, we determined that Tim-3 controls glycolysis in macrophages and thus contributes to phenotype shifting. Tim-3 signal blockade significantly increases lactate production by macrophages, but does not influence cell proliferation or apoptosis. Tim-3 attenuates glucose uptake by inhibiting hexokinase 2 (HK2) expression in macrophages. Tim-3-mediated inhibition of macrophage glycolysis and the expression of proinflammatory cytokines, tumour necrosis factor (TNF)-α and interleukin (IL)-1β are reversed by HK2 silencing. Finally, we demonstrated that Tim-3 inhibits HK2 expression via the STAT1 pathway. We have thus discovered a new way by which Tim-3 modulates macrophage function.

Negative regulation of Nod-like receptor protein 3 inflammasome activation by T cell Ig mucin-3 protects against peritonitis

The Nod-like receptor protein 3 (NLRP3) inflammasome plays roles in host defence against invading pathogens and in the development of autoimmune damage. Strict regulation of these responses is important to avoid detrimental effects. Here, we demonstrate that T cell Ig mucin-3 (Tim-3), an immune checkpoint inhibitor, inhibits NLRP3 inflammasome activation by damping basal and lipopolysaccharide-induced nuclear factor-κB-mediated up-regulation of NLRP3 and interleukin-1β during the priming step and basal and ATP/lipopolysaccharide-induced ATP production, K⁺ efflux, and reactive oxygen species production during the activation step. Residues Y256/Y263 in the C-terminal region of Tim-3 are required for these inhibitory effects on the NLRP3 inflammasome. In mice with alum-induced peritonitis, blockade of Tim-3 exacerbates peritonitis by overcoming the inhibitory effect of Tim-3 on NLRP3 inflammasome activation, while transgenic expression of Tim-3 attenuates inflammation by inhibiting NLRP3 inflammasome activation. Our results show that Tim-3 is a critical negative regulator of NLRP3 inflammasome and provides a potential target for intervention of diseases with uncontrolled inflammasome activation.

Tim-3 promotes tumor-promoting M2 macrophage polarization by binding to STAT1 and suppressing the STAT1-miR-155 signaling axis

T cell Ig mucin-3 (Tim-3), an immune checkpoint inhibitor, shows therapeutic potential. However, the molecular mechanism by which Tim-3 regulates immune responses remains to be determined. In particular, very little is known about how Tim-3 works in innate immune cells. Here, we demonstrated that Tim-3 is involved in the development of tumor-promoting M2 macrophages in colon cancer. Manipulation of the Tim-3 pathway significantly affected the polarization status of intestinal macrophages and the progression of colon cancer. The Tim-3 signaling pathway in macrophages was explored using microarray, co-immunoprecipitation, gene mutation, and high-content analysis. For the first time, we demonstrated that Tim-3 polarizes macrophages by directly binding to STAT1 via residue Y256 and Y263 in its intracellular tail and inhibiting the STAT1-miR-155-SOCS1 signaling axis. We also identified a new signaling adaptor of Tim-3 in macrophages, and, by modulating the Tim-3 pathway, demonstrated the feasibility of altering macrophage polarization as a potential tool for treating this kind of disease.

Ruminococcus gnavus E1 modulates mucin expression and intestinal glycosylation

AIMS

The molecular cross-talk between commensal bacteria and the gut play an important role in the maintenance of the intestinal homeostasis and general health. Here, we studied the impact of a major Gram-positive anaerobic bacterium of the human gut microbiota, that is, Ruminococcus gnavus on the glycosylation pattern and the production of intestinal mucus by the goblet cells.

METHODS AND RESULTS

Our results showed that R. gnavus E1 specifically increases the expression and the glycosylation level of the intestinal glyco-conjugates by goblet cells in the colonic mucosa of mono-associated mice with R. gnavus E1 as well as in human HT29-MTX cells. Such an effect was mediated through induction of the level of mRNA encoding for the major intestinal gel-forming mucin such as MUC2 and various glycosyltransferase enzymes.

CONCLUSIONS

This study demonstrates for the first time that R. gnavus E1 possess the ability to modulate the glycosylation profile of the glyco-conjugate molecules and mucus in goblet cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

Furthermore, we demonstrated that R. gnavus E1 modified specifically the glycosylation pattern and MUC2 expression by means of a small soluble factor of peptidic nature (<3 kDa) and heat stable in the HT29-MTX cell.

Tumor pretargeting in mice using MORF conjugated CC49 antibody and radiolabeled complimentary cMORF effector

AIM

Using the antiCEA antibody MN14, a LS174T mouse tumor model has been successfully targeted with (⁹⁹m)Tc for imaging and ¹⁸⁸Re for radiotherapy by phosphorodiamidate morpholino oligomers (MORF)/complementary MORF (cMORF) pretargeting strategy. This investigation evaluated the antiTAG-72 antibody CC49 as an alternative to MN14 for this application.

METHODS

Both CC49 and MN14 were labeled with ¹¹¹In via SCN-benzyl-DTPA and their biodistributions were compared to that of MN14 labeled via DTPA anhydride. Since the accessibility of the antibody to the effector is required for optimization of pretargeting, the internalization of both MORF-CC49 and MORF-MN14 antibodies in LS174T cells were evaluated in culture. In addition, the accessible concentration of MORF-CC49 antibody in tumor was determined in a series of pretargeting studies with escalating dosages of the [(⁹⁹m)Tc]cMORF effector. Finally, using these results and our semi-empirical model, an imaging study was performed under optimal pretargeting conditions.

RESULTS

The biodistribution of ¹¹¹In to trace the MN14 antibody depended significantly on the labeling method. Furthermore, both MORF-CC49 and MORF-MN14 antibodies showed rapid internalization in culture. Fortunately, the accessibility in tumor was found to be less seriously reduced in vivo. In a pretargeting study under optimal conditions, both by imaging and by necropsy, the [(⁹⁹m)Tc]cMORF effector accumulated predominantly in the tumor of pretargeted mice. Normal tissue accumulations were minimal except in kidneys, liver, and a segment of intestines.

CONCLUSION

MORF pretargeting with CC49 was equally successful in the LS174T tumor model to the MORF pretargeting with MN14. The MORF-CC49 antibody may therefore be considered for future investigations toward early clinical trials.

Dielectric scaling in polyelectrolyte solutions with different solvent quality in the dilute concentration regime

In this note, we present a set of radiowave dielectric spectroscopy measurements of two dilute, differently-charged polyelectrolyte solutions, under different solvent conditions. We have found that both the dielectric strength, Delta epsilon, and the relaxation time, tau(ion), of the dielectric relaxation process associated with the counterion polarization along a length scale of the order of the correlation length obey the scaling laws with the polyion concentration, according to the Ito model. This is verified with good accuracy independently of the quality of the solvent, which has been varied from poor to good solvent conditions. This finding supports evidence to the fact that, in dilute solutions, the counterion polarization is independent of the polyion concentration, in spite of what occurs at the semi-dilute concentrations.

Solvent quality influence on the dielectric properties of polyelectrolyte solutions: a scaling approach

The dielectric properties of polyelectrolytes in solvent of different quality have been measured in an extended frequency range and the dielectric parameters associated with the polarization induced by counterion fluctuation over some peculiar polyion lengths have been evaluated. Following the scaling theory of polyelectrolyte solutions and the recent models developed by Dobrynin and Rubinstein that explicitly take into account the quality of the solvent on the polyion chain conformation, we have reviewed and summarized a set of scaling laws that describe the dielectric behavior of these systems in the dilute and semidilute regime. Moreover, for poorer solvents, where theory of hydrophobic polyelectrolytes predicts, and computer simulation confirms, a particular chain structure consisting of partially collapsed monomers (beads) connected by monomer strings, we derived a scaling law. These predictions are compared with the results obtained from the dielectric parameters (the dielectric increment delta epsilon and the relaxation time tau(ion)) of the "intermediate" frequency relaxation of two partially charged polymers, which possess a carbon-based backbone for which water is a poor solvent and ethylene glycol is a good solvent. By varying the solvent composition (a water-ethylene glycol mixture), we have tuned the quality of the solvent, passing from poor to good condition and have observed the predicted scaling for all the systems investigated. These findings give a further support to the scaling theory of polyelectrolyte solutions and to the necklace model for hydrophobic polyelectrolytes in poor solvents.

Conductometric properties of linear polyelectrolytes in poor-solvent condition: The necklace model

We present a set of low-frequency electrical conductivity measurements of solutions of differently charged, salt-free polyelectrolytes in poor- and in good-solvent conditions, in the semidilute concentration regime. The data have been analyzed and discussed in light of the necklace model for hydrophobic polyelectrolytes recently proposed by Dobrynin et al. [Macromolecules 29, 2974 (1996)] that predicts the chains to collapse into spheroidal cores connected by narrow strings. By varying the quality of the solvent, we have measured the polyion equivalent conductance lambda(p) in an extended concentration range in the semidilute regime and have demonstrated that this parameter is influenced by the polyion chain conformation, giving further support, when the poor-solvent condition prevails, to the picture of a string of electrostatic blobs. On the contrary, in good-solvent condition, the electrical conductivity data are in reasonable good agreement with the picture of an extended chain consisting of a collection of electrostatic blobs. These electrical conductivity measurements, in light of scaling theory, furnish new experimental support for the necklace model for hydrophobic polyions in poor solvents.

Evidence of antisense tumor targeting in mice

Even though increased accumulations of radiolabeled antisense DNAs compared to control DNAs are becoming a routine observation in cultured tumor cells, trustworthy evidence of tumor targeting in vivo by an antisense mechanism remains elusive. The goal of this study was to obtain convincing evidence of antisense tumor targeting in nude mice by using two different tumors and both intratumoral (i.t.) and intravenous (i.v.) administration of radiolabeled antisense and control sense DNAs. Both the MDR++ cell line KB-G2 and its parent MDR+ cell line KB-31 were used in this study. The antisense (AS) DNA was directed against the AUG start codon of the MDR1 mRNA and, along with the sense (S) control DNA, was a uniform phosphorothioate administered naked. In previous cell culture studies from our laboratories, the accumulation of this AS DNA was strikingly high in KB-G2 cells and only average in KB-31 cells, a fact we attribute to the 1000-fold higher expression by RT-PCR of MDR1 mRNA in the former cell line. In this study, both DNAs were radiolabeled with (99m)Tc via MAG3 and administered i.t. or i.v. at 1 microg (100 microCi) per animal 24 h prior to sacrifice and dissection in mice bearing thigh tumors of about 1 g. Following i.t. administration, no statistically significant differences (Student's t test, p < 0.05, N = 4) between the AS and S DNA biodistributions in normal tissues were observed except in the KB-G2 mice in which muscle levels were lower for the S control. In contrast, tumor levels in the KB-G2 animals were significantly higher for the AS DNA vs S DNA (14.7 vs 8.5% ID/g) while this difference (8.6 vs 4.3% ID/g) was insignificant in the KB-31 animals. The whole body images obtained just prior to sacrifice clearly show improved targeting of AS DNA vs S DNA in the KB-G2 but not the KB-31 animals. Calculations based on these results show that about 60 000 AS DNAs accumulated specifically (i.e. AS DNA - S DNA) per KB-G2 tumor cell following i.t. administration. When administered i.v. rather than i.t., higher tumor levels in KB-G2 animals compared to KB-31 were not observed, most likely because of the lower dosage reaching the tumors. When the KB-G2 and KB-31 results are combined, no statistically significant differences between the AS and S DNA biodistributions in normal tissues were observed except in blood in which S DNA levels were higher and in spleen in which they were lower. In contrast, tumor levels were significantly higher for the AS DNA vs S DNA (0.100 vs 0.063% ID/g). Calculations based on these results show that about 400 AS DNAs accumulated specifically per tumor cell following i.v. administration. Therefore evidence for tumor targeting in vivo by an antisense mechanism has been obtained in that statistically higher tumor accumulations of the (99m)Tc-AS DNA were observed compared to the control (99m)Tc-S DNA both following i.t. and i.v. administrations. The successful localization of AS DNA in tumor demonstrates that in vivo AS targeting of tumor is feasible although improvements in tumor delivery and normal tissue clearance are needed for practical antisense imaging.

5' dinucleotide repeat polymorphism of NRAMP1 and susceptibility to tuberculosis among Caucasian patients in Houston, Texas

SETTING

Houston Tuberculosis Initiative (HTI) and Baylor College of Medicine, Houston, Texas.

OBJECTIVE

To further explore the association between the polymorphisms of NRAMP1 and human susceptibility/resistance to tuberculosis (TB), specifically to determine whether the reported association shown for blacks and Asians holds true for Caucasian populations.

DESIGN

In a case-control study, 135 adult Caucasian TB patients and 108 adult Caucasian HIV-seronegative non-TB controls were analyzed for the association between the polymorphisms in NRAMP1 gene and clinical TB.

RESULTS

Heterozygote at 5'(GT)n, a dinucleotide repeat polymorphism in the promoter of NRAMP1, was observed at significantly higher frequencies among HIV-negative patients with pulmonary TB (41.6%; OR 2.02; 95%CI 1.11-3.64), extra-pulmonary TB (66.7%; OR 4.80; 95%CI 1.34-17.15), and HIV-seropositive TB patients (50%; OR 3.77; 95%CI 1.33-10.66) in comparison with the controls (27.8%). Homozygotes (GT)(10,10) were over-represented among HIV-positive TB patients (18.2%; OR 6.86; 95%CI 1.55-30.21) compared to the controls (5.5%).

CONCLUSION

These findings suggest that the 5'(GT)n polymorphism of NRAMP1 modifies TB susceptibility in this Caucasian population, and could possibly be related to the site of infection among HIV-negative individuals and HIV-coinfected TB.

[MRI diagnosis of painful ophthalmoplegia syndrome]

OBJECTIVE

To study MRI appearances of painful ophthalmoplegia syndrome and provide image basis for clinical diagnosis of painful ophthalmoplegia syndrome.

METHODS

Seventeen cases with painful ophthalmoplegia syndrome diagnosed clinically were collected. MRI ordinary scan and gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) contrast fatty-restraint scan were performed on the orbit and cavernous sinus.

RESULTS

MRI appearances of painful ophthalmoplegia syndrome included patch or small nodule abnormal signal at the region of fissura orbitalis superior. The ipsilateral cavernous sinus was enlarged. The local lobus temporalis meninges close to the fissura orbitalis superior and cavernous sinus were invaded. MRI contrast fatty-restraint scan might clearly show the pathological changes.

CONCLUSION

MRI may provide image basis for the clinical diagnosis of painful ophthalmoplegia syndrome.

Expression of bright at two distinct stages of B lymphocyte development

The B cell regulator of Ig heavy chain transcription (Bright) is a DNA-binding protein that was originally discovered in a mature Ag-specific B cell line after stimulation with IL-5 and Ag. It binds to the intronic heavy chain enhancer and 5' of the V1 S107 family V(H) promoter. Several studies suggested that Bright may increase transcription of the heavy chain locus, and expression in cell lines was limited to those representing mature B cells. We have now analyzed normal hemopoietic tissues for the expression of Bright during B lymphocyte differentiation. We expected to find Bright expression in a subset of mature spleen cells, but also observed Bright in a subset of normal B lymphocytic progenitors in both adult bone marrow (BM) and in fetal liver as early as day 12 of gestation. Bright was also expressed in the small percentage of CD4(low) cells in the thymus that are newly arrived from the BM and are not yet committed to the T lymphocyte lineage, but was not observed at later stages of T cell differentiation in either the spleen or thymus. Bright mRNA was not detected in the immature B lymphocytes that initially populate the spleen after migration from the BM. In addition, new splice variants of Bright were observed in fetal tissues. Thus, Bright expression is highly regulated in normal murine lymphocytes and occurs both early and late during B cell differentiation. These findings may have important implications for the function of Bright in regulating Ig transcription.

Family-specific differences in transcription efficiency of Ig heavy chain promoters

Murine Ig variable region heavy chain genes (V(H)) are grouped into families based on coding sequence homology. We observed that the accompanying promoter sequences were also conserved in a family-specific manner. Remarkably, no one has directly compared the transcription efficiencies of V(H) genes from different families. Using an in vitro transcription system, we found that transcription efficiencies of different V(H) promoters differed by as much as 70-fold. These differences could be attributed to variation in the octamer-heptamer and TATA sequences, as well as to the presence or absence of initiator elements. The J558 family promoter exhibited the highest level of transcription and specifically interacted with an Oct-1 dimer not bound by other V(H) promoters. These data suggest that differential transcription and regulation of V(H) promoters could occur in vivo. The increased transcription efficiency of the J558 promoter relative to other V(H) promoters also presents a possible explanation for the abundance of J558 sterile transcripts observed before V(H)DJ(H) rearrangement.

Family-specific differences in transcription efficiency of Ig heavy chain promoters

Murine Ig variable region heavy chain genes (V(H)) are grouped into families based on coding sequence homology. We observed that the accompanying promoter sequences were also conserved in a family-specific manner. Remarkably, no one has directly compared the transcription efficiencies of V(H) genes from different families. Using an in vitro transcription system, we found that transcription efficiencies of different V(H) promoters differed by as much as 70-fold. These differences could be attributed to variation in the octamer-heptamer and TATA sequences, as well as to the presence or absence of initiator elements. The J558 family promoter exhibited the highest level of transcription and specifically interacted with an Oct-1 dimer not bound by other V(H) promoters. These data suggest that differential transcription and regulation of V(H) promoters could occur in vivo. The increased transcription efficiency of the J558 promoter relative to other V(H) promoters also presents a possible explanation for the abundance of J558 sterile transcripts observed before V(H)DJ(H) rearrangement.

Reassessment of germline heavy chain transcripts from two murine VH families

While expression of functional heavy chain immunoglobulin mRNA requires rearrangement of variable (VH), diversity (D) and (JH) gene segments, these individual gene segments can be transcribed prior to their rearrangement. It has been proposed that the resulting germline, or sterile, transcripts play an important role in the rearrangement process because strong correlations between rearrangement frequency and sterile transcript levels have been observed in some studies. Murine VH genes have been grouped into families on the basis of coding sequence homology. VH families rearrange in a developmentally regulated manner, so that rearrangements of genes from several VH families are detected earlier than rearrangements of J558 family genes. Paradoxically, the only VH family for which sterile transcripts have been documented is the J558 family. We used RT-PCR analyses to ask whether sterile transcripts from other VH families could be detected in fetal liver samples prior to their rearrangement. While J558 family germline transcripts were easily detected, no sterile transcripts were observed from the S107 family. Our studies also revealed the ability of small quantities of degraded genomic DNA to nonspecifically prime cDNA synthesis, emphasizing the need for caution in interpreting RT-PCR data in which family-specific oligos are used for cDNA production. These results cast doubt on the idea that sterile transcripts are required for V(H)DJ(H) rearrangement.

The recombination signal sequence-binding protein RBP-2N functions as a transcriptional repressor

We have identified a cellular protein, RBP-2N, a presumed recombinase, as a repressor of transcription. Inhibition of transcription by RBP-2N was dependent on its DNA recognition site and was demonstrated in vitro and in vivo. This repression appears to be general, as transcription mediated by SP1 and Gal4/VP16 was inhibited by RBP-2N. The protein was purified to near homogeneity from human cells on the basis of its binding to a site present in the promoter of the adenovirus pIX gene. The DNA recognition sequence is 5'-TGGGAAAGAA, which is markedly different from the recombination signal sequence originally identified as the target site for this protein. The sequence of the purified protein is 97% identical with that published for the mouse RBP-2N protein. The reported homolog in Drosophila is Suppressor of Hairless. RBP-2N binding sites are present in a number of cellular and viral promoters, so RBP-2N may have a general role in transcriptional repression.

Single missense mutation in the tyrosine kinase catalytic domain of the RET protooncogene is associated with multiple endocrine neoplasia type 2B

Multiple endocrine neoplasia type 2B (MEN 2B) is a human cancer syndrome characterized by medullary thyroid carcinoma (MTC), pheochromocytomas, mucosal neuromas, ganglioneuromas of the intestinal tract, and skeletal and ophthalmic abnormalities. It appears both as an inherited disorder and as de novo disease. Sequence analysis of germ-line DNA from MEN 2B patients revealed the existence of the same point mutation in the RET protooncogene in 34 unrelated individuals. This sequence difference was not observed in 93 unaffected individuals, including the normal parents of 14 de novo MEN 2B patients. The mutation (ATG-->ACG) results in the replacement of methionine with threonine within the catalytic core region of the tyrosine kinase domain. We propose that this amino acid replacement effects substrate interactions and results in dominant oncogenic activity by the RET protein. Missense mutations in the extracellular ligand-binding domain of the RET protooncogene previously have been associated with two other disorders [MEN 2A and familial MTC (FMTC)] in which MTC is observed. MEN 2B represents the third form of heritable MTC known to be an allele of RET. Alterations in two different functional domains of the putative receptor protein tyrosine kinase are implicated in development of MTC.

Mutations in the RET proto-oncogene are associated with MEN 2A and FMTC

Multiple endocrine neoplasia type 2A (MEN 2A) and familial medullary thyroid carcinoma (FMTC) are dominantly inherited conditions which predispose to the development of endocrine neoplasia. Evidence is presented that sequence changes within the coding region of the RET proto-oncogene, a putative transmembrane tyrosine kinase, may be responsible for the development of neoplasia in these inherited disorders. Single strand conformational variants (SSCVs) in exons 7 and 8 of the RET proto-oncogene were identified in eight MEN 2A and four FMTC families. The variants were observed only in the DNA of individuals who were either affected or who had inherited the MEN2A or FMTC allele as determined by haplotyping experiments. The seven variants identified were sequenced directly. All involved point mutations within codons specifying cysteine residues, resulting in nonconservative amino acid changes. Six of the seven mutations are located in exon 7. A single mutation was found in exon 8. Variants were not detected in four MEN 2B families studied for all exon assays available, nor were they detectable in 16 cases of well documented sporadic medullary thyroid carcinoma or pheochromocytoma that were tested for exon 7 variants. Coinheritance of the mutations with disease and the physical and genetic proximity of the RET proto-oncogene provide evidence that RET is responsible for at least two of the three inherited forms of MEN 2. Neither the normal function, nor the ligand of RET are yet known. However, its apparent involvement in the development of these inherited forms of neoplasia as well as in papillary thyroid carcinoma suggest an important developmental or cell regulatory role for the protein.

Identification of a human achaete-scute homolog highly expressed in neuroendocrine tumors

Basic helix-loop-helix transcription factors of the achaete-scute family are instrumental in Drosophila neurosensory development and are candidate regulators of development in the mammalian central nervous system and neural crest. We report the isolation and initial characterization of a human achaete-scute homolog that is highly expressed in two neuroendocrine cancers, medullary thyroid cancer (MTC) and small cell lung cancer (SCLC). The human gene, which we have termed human achaete-scute homology 1 (hASH1), was cloned from a human MTC cDNA library. It encodes a predicted protein of 238 aa that is 95% homologous to mammalian achaete-scute homolog (MASH) 1, a rodent basic helix-loop-helix factor. The 57-residue basic helix-loop-helix domain is identical to that in the rodent gene, and the basic and helical regions, excluding the loop, are 72-80% identical to Drosophila achaete-scute family members. The proximal coding region of the hASH1 cDNA contains a striking 14-copy repeat of the triplet CAG that exhibits polymorphism in human genomic DNA. Thus, hASH1 is a candidate locus for disease-causing mutations via triplet repeat amplification. Analysis of rodent-human somatic cell hybrids permitted assignment of hASH1 to human chromosome 12. Northern blots revealed hASH1 transcripts in RNA from a human MTC cell line, two fresh MTC tumors, fetal brain, and three lines of human SCLC. In contrast, cultured lines of non-SCLC lung cancers and a panel of normal adult human tissues showed no detectable hASH1 transcripts. Expression of hASH1 may provide a useful marker for cancers with neuroendocrine features and may contribute to the differentiation and growth regulation of these cells.

Development of a sequence-tagged site for the centromere of chromosome 10: its use in cytogenetic and physical mapping

We sequenced the alphoid centromere probe p alpha 10RP8 (D10Z1), aligned it to three published consensus sequences, and developed a sequence-tagged site (STS), sJRH-2, based upon oligonucleotide primers having two 3' mismatches with these consensus sequences. Polymerase chain reaction (PCR) amplification using genomic DNA from a somatic cell hybrid panel representing all human chromosomes demonstrated amplification from only those cell lines containing chromosome 10. Fluorescence in situ hybridization of the amplified product demonstrated intense and specific hybridization of the PCR product to 10p11.1-q11.1. A human genomic yeast artificial chromosome (YAC) library was screened using the sJRH-2 PCR assay, and five clones were identified. Sequence analysis of one chimeric clone (consisting of DNA segments derived from chromosomes 5p and 10cen) confirmed specificity of the STS for the centromere of chromosome 10. sJRH-2 provides a convenient cytogenetic marker for chromosome 10, which will also be useful for physical mapping of the pericentromeric region of chromosome 10, a region that harbors the gene(s) for three forms of multiple endocrine neoplasia (types 2A, 2B, and familial medullary thyroid carcinoma). The GenBank accession number for the p alpha 10RP8 sequence is X63622.

A 1.5-megabase yeast artificial chromosome contig from human chromosome 10q11.2 connecting three genetic loci (RET, D10S94, and D10S102) closely linked to the MEN2A locus

The genetic loci RET, D10S94, and D10S102 from human chromosome 10q11.2 are very closely linked to a locus responsible for the multiple endocrine neoplasia type 2 (MEN2A and MEN2B) and medullary thyroid carcinoma (MTC1) familial cancer syndromes. We have constructed a 1.5-megabase contig consisting of six genomic yeast artificial chromosome clones which include these loci and define their physical order. A critical crossover event has been identified within the map interval; this event places the MEN2A locus centromeric to D10S102 and defines the orientation of the physical map on the chromosome. The orientation of the contig and order of the markers are centromere-RET-D10S94-D10S102-telomere. In addition, a microsatellite repeat polymorphism with a heterozygosity of 71% at the RET locus and a restriction fragment length polymorphism with a heterozygosity of 42% detected by a lambda clone from the D10S94 locus have been developed for high-resolution genetic linkage mapping and predictive diagnostic testing. These data place three important markers on a contiguous physical map, narrow the MEN2 disease locus interval, and provide a framework for further candidate gene identification efforts. Placement of these genetic loci along a clone-based map and continued expansion of the contig will also facilitate efforts to determine the relationship of physical to genetic distance near the centromeres of human chromosomes.

Improved predictive test for MEN2, using flanking dinucleotide repeats and RFLPs

Gene(s) for the autosomal dominant endocrine cancer syndromes, multiple endocrine neoplasia type 2A (MEN2A), multiple endocrine neoplasia type 2B (MEN2B), and familial medullary thyroid carcinoma (MTC1) all map to the pericentromeric region of chromosome 10. Predictive testing for the inheritance of mutant alleles in individuals at risk for these disorders has been limited by the availability of highly informative and closely linked flanking markers. We describe the development of eight new markers, including two PCR-based dinucleotide repeat polymorphisms and six RFLPs that flank the disease loci. One of the dinucleotide repeat markers (sJRH-1) derives from the RBP3 locus on 10q11.2 and has a PIC of .88. The other dinucleotide repeat (sTCL-1) defines a new locus, D10S176, that maps by in situ hybridization to 10p11.2 and has a PIC of .68. We have constructed a new genetic linkage map of the pericentromeric region of chromosome 10, on the basis of 13 polymorphisms at six loci, which places the MEN2A locus between the dinucleotide repeat markers, with odds of 5,750:1 over the next most likely position. Using this set of markers, predictive genetic testing of 130 at-risk individuals from six families segregating MEN2A revealed that 95% were jointly informative with flanking markers, representing a significant improvement in genetic testing capabilities.

Presymptomatic identification of carriers of the multiple endocrine neoplasia type 2A gene using flanking DNA markers

BACKGROUND

Because the predisposition locus for multiple endocrine neoplasia type 2A (MEN2A) has been mapped to chromosome 10 by genetic linkage analysis, it has become possible to identify gene carriers by following the transmission of linked genetic markers from affected parents to offspring at risk for MEN2A. We have applied a highly accurate genetic test to presymptomatic diagnosis of gene carriers in several large kindreds with MEN2A.

METHODS

DNA was extracted from 300 individuals in six kindreds with MEN2A and used for genotyping studies with DNA markers flanking the MEN2A locus. Genotype data were used to predict the inheritance of the MEN2A gene in kindred members at risk according to previously calculated map distances and the program LINKAGE:

RESULTS

Ninety-five percent of individuals were informative with markers flanking the MEN2A locus. Of 130 patients at risk, 26 (20%) were predicted to be MEN2A gene carriers, 100% (77%) were noncarriers, and 4 (3%) were recombinant and their gene carrier status could not be determined. Gene carrier prediction probabilities were calculated at greater than 98% in 94% of these patients.

CONCLUSIONS

We conclude that genetic testing with flanking DNA markers is a highly accurate method for the presymptomatic identification of MEN2A gene carriers and allows for diagnosis at an earlier stage than does traditional calcitonin testing.

Isolation of YAC clones from the pericentromeric region of chromosome 10 and development of new genetic markers linked to the multiple endocrine neoplasia type 2A gene

Genetic linkage mapping and contig assembly using yeast artificial chromosome (YAC) technology form the basis of our strategy to clone and define the genomic structure of the pericentromeric region of chromosome 10 containing the multiple endocrine neoplasia type 2A gene. Thus far YAC walks have been initiated from five chromosome 10 pericentromeric loci including RBP3, D10S94, RET, D10Z1, and FNRB. Long range pulsed-field gel electrophoresis maps are constructed from the YACs isolated to define clone overlaps and to identify putative CpG islands. Bidirectional YAC walks are continued by rescreening the YAC library with sequence-tagged site assays developed from end-clones. Several new restriction fragment length polymorphisms and simple sequence repeat polymorphism markers have been identified from the YAC clones. In particular, two highly informative (CA)n dinucleotide repeat markers, sTCL-1 from proximal chromosome 10p (16 alleles, PIC = 0.68) and sJRH-1 from the RBP3 locus (18 alleles, PIC = 0.88), provide useful reagents for a polymerase chain reaction-based predictive genetic test that can be performed rapidly from small amounts of DNA.

A new RFLP locus D4S185 maps to human chromosome 4q

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