Palmoplantar keratoderma caused by a missense variant in CTSB encoding cathepsin B.

BACKGROUND: Palmoplantar keratoderma (PPK) refers to a large group of disorders characterized by extensive genetic and phenotypic heterogeneity. PPK diagnosis therefore increasingly relies upon genetic analysis. AIM: To delineate the genetic defect underlying a case of diffuse erythematous PPK associated with peeling of the skin. METHODS: Whole exome and direct sequencing, real-time quantitative PCR, protein modelling and a cathepsin B enzymatic assay were used. RESULTS: The patient studied had severe diffuse erythematous PPK transgrediens. Pedigree analysis suggested an autosomal dominant mode of inheritance. Whole exome sequencing revealed a heterozygous missense mutation in the CTSB gene, encoding the cysteine protease cathepsin B. Genomic duplications in a noncoding region, which regulates the expression of CTSB, were recently found to cause erythrokeratolysis hiemalis, a rare autosomal dominant disorder of cornification. This mutation affects a highly conserved residue, and is predicted to be pathogenic. Protein modelling indicated that the mutation is likely to lead to increased endopeptidase cathepsin B activity. Accordingly, the CTSB variant was found to result in increased cathepsin B proteolytic activity. CONCLUSION: In summary, we report the identification of the first gain-of-function missense mutation in CTSB, which was found to be associated in one individual with a dominant form of diffuse PPK.

ERBIN deficiency links STAT3 and TGF-ß pathway defects with atopy in humans.

Nonimmunological connective tissue phenotypes in humans are common among some congenital and acquired allergic diseases. Several of these congenital disorders have been associated with either increased TGF-ß activity or impaired STAT3 activation, suggesting that these pathways might intersect and that their disruption may contribute to atopy. In this study, we show that STAT3 negatively regulates TGF-ß signaling via ERBB2-interacting protein (ERBIN), a SMAD anchor for receptor activation and SMAD2/3 binding protein. Individuals with dominant-negative STAT3 mutations (STAT3mut ) or a loss-of-function mutation in ERBB2IP (ERBB2IPmut ) have evidence of deregulated TGF-ß signaling with increased regulatory T cells and total FOXP3 expression. These naturally occurring mutations, recapitulated in vitro, impair STAT3-ERBIN-SMAD2/3 complex formation and fail to constrain nuclear pSMAD2/3 in response to TGF-ß. In turn, cell-intrinsic deregulation of TGF-ß signaling is associated with increased functional IL-4Rα expression on naive lymphocytes and can induce expression and activation of the IL-4/IL-4Rα/GATA3 axis in vitro. These findings link increased TGF-ß pathway activation in ERBB2IPmut and STAT3mut patient lymphocytes with increased T helper type 2 cytokine expression and elevated IgE.

Thymus transplantation restores the repertoires of forkhead box protein 3 (FoxP3)+ and FoxP3- T cells in complete DiGeorge anomaly.

The development of T cells with a regulatory phenotype after thymus transplantation has not been examined previously in complete DiGeorge anomaly (cDGA). Seven athymic infants with cDGA and non-maternal pretransplantation T cell clones were assessed. Pretransplantation forkhead box protein 3 (Foxp3)(+) T cells were detected in five of the subjects. Two subjects were studied in greater depth. T cell receptor variable ß chain (TCR-Vß) expression was assessed by flow cytometry. In both subjects, pretransplantation FoxP3(+) and total CD4(+) T cells showed restricted TCR-Vß expression. The development of naive T cells and diverse CD4(+) TCR-Vß repertoires following thymic transplantation indicated successful thymopoiesis from the thymic tissue grafts. Infants with atypical cDGA develop rashes and autoimmune phenomena before transplantation, requiring treatment with immunosuppression, which was discontinued successfully subsequent to the observed thymopoiesis. Post-transplantation, diverse TCR-Vß family expression was also observed in FoxP3(+) CD4(+) T cells. Interestingly, the percentages of each of the TCR-Vß families expressed on FoxP3(+) and total CD4(+) T cells differed significantly between these T lymphocyte subpopulations before transplantation. By 16 months post-transplantation, however, the percentages of expression of each TCR-Vß family became significantly similar between FoxP3(+) and total CD4(+) T cells. Sequencing of TCRBV DNA confirmed the presence of clonally amplified pretransplantation FoxP3(+) and FoxP3(-) T cells. After thymus transplantation, increased polyclonality was observed for both FoxP3(+) and FoxP3(-) cells, and pretransplantation FoxP3(+) and FoxP3(-) clonotypes essentially disappeared. Thus, post-transplantation thymic function was associated with the development of a diverse repertoire of FoxP3(+) T cells in cDGA, corresponding with immunological and clinical recovery.

Loss of mucosal CD103+ DCs and IL-17+ and IL-22+ lymphocytes is associated with mucosal damage in SIV infection.

Human immunodeficiency virus (HIV) and Simian immunodeficiency virus (SIV) disease progression is associated with multifocal damage to the gastrointestinal tract epithelial barrier that correlates with microbial translocation and persistent pathological immune activation, but the underlying mechanisms remain unclear. Investigating alterations in mucosal immunity during SIV infection, we found that damage to the colonic epithelial barrier was associated with loss of multiple lineages of interleukin (IL)-17-producing lymphocytes, cells that microarray analysis showed expressed genes important for enterocyte homeostasis, including IL-22. IL-22-producing lymphocytes were also lost after SIV infection. Potentially explaining coordinate loss of these distinct populations, we also observed loss of CD103+ dendritic cells (DCs) after SIV infection, which associated with the loss of IL-17- and IL-22-producing lymphocytes. CD103+ DCs expressed genes associated with promotion of IL-17/IL-22+ cells, and coculture of CD103+ DCs and naïve T cells led to increased IL17A and RORc expression in differentiating T cells. These results reveal complex interactions between mucosal immune cell subsets providing potential mechanistic insights into mechanisms of mucosal immune dysregulation during HIV/SIV infection, and offer hints for development of novel therapeutic strategies to address this aspect of AIDS virus pathogenesis.

Heterophile antibodies indicate progression of autoimmunity in human type 1 diabetes mellitus before clinical onset.

We previously reported serum cytokines in a group of long term non-progressors to Type 1 diabetes; this reactivity detected in ELISA is now identified as heterophile antibody in some sera. Here, we characterize heterophile antibody activity. A 14 kDa-polypeptide from heterophile antibody containing serum bound to an anti-IL-4 column, but IL-4 was not detected by Western blot or by MS/MS sequencing. However, in 2/13 heterophile antibody positive sera, T-cell growth was potentiated and was blocked by an anti-human immunoglobulin. To examine the relationship between low affinity heterophile antibody presence and disease progression, 1100 archived serum samples were analyzed with two pairs of antibodies from 443 diabetes-free first degree relatives of Type 1 diabetes mellitus patients for heterophile antibody; 95 individuals developed diabetes on follow-up. Twenty-two individuals, whose serum was heterophile antibody positive with the second pair of antibodies (but negative with the first pair of antibodies), had a significantly higher incidence of developing diabetes after five years. Thirty-seven individuals with heterophile antibody reactivity with the first pair of antibodies, regardless of reactivity with the second pair of antibodies, had a significantly lower incidence of developing diabetes. While we cannot exclude the presence of genuine cytokine in all sera, these data indicate the presence of distinct groups of heterophile antibodies in patients at high risk to develop diabetes. Thus, anti-Ig heterophilic antibodies with different immunochemical reactivities are linked to the progression of or protection from Type 1 diabetes autoimmunity.

Expression and localization of serum resistance associated protein in Trypanosoma brucei rhodesiense.

The trypanosome lytic factor (TLF) is a primate specific innate defense mechanism that restricts the host range of African trypanosomes. Trypanosoma brucei rhodesiense, the causative agent of the acute form of human sleeping sickness, is resistant to the cytolytic action of TLF. By differential display PCR we have identified a gene in T. b. rhodesiense that is preferentially expressed in cell lines resistant to TLF. The protein sequence predicted from the gene shows homology to the trypanosome variable surface glycoprotein (VSG) gene family and in particular, to the previously reported human serum resistance associated gene (SRA). The amount of SRA mRNA is over 1000-fold higher in TLF resistant cells relative to TLF sensitive trypanosomes. Treatment of TLF sensitive trypanosomes with increasing concentrations of TLF in mice results in the selection of parasites that have reverted back to the TLF resistant phenotype. These trypanosomes also showed high levels of SRA mRNA. Antibodies against recombinant SRA react with a 59 kDa protein on western blots of total cell protein from TLF resistant trypanosomes but not TLF sensitive cells. Indirect immunofluorescence revealed that SRA is a cell surface protein present only in TLF resistant trypanosomes. These results suggest that TLF resistance in human sleeping sickness trypanosomes is a consequence of the selective, high level expression of a cell surface molecule(s). In addition, these studies support the role of TLF as a major factor in human serum mediated killing of susceptible trypanosomes.

Differential responses of invariant V alpha 24J alpha Q T cells and MHC class II-restricted CD4+ T cells to dexamethasone.

NK T cells are a T cell subset in the human that express an invariant alpha-chain (V alpha 24invt T cells). Because of the well-described immunomodulation by glucocorticoids on activation-induced cell death (AICD), the effects of dexamethasone and anti-CD3 stimulation on V alpha 24invt T cell clones and CD4+ T cell clones were investigated. Dexamethasone significantly enhanced anti-CD3-mediated proliferation of V alpha 24invt T cells, whereas CD4+ T cells were inhibited. Addition of neutralizing IL-2 Ab partially abrogated dexamethasone-induced potentiation of V alpha 24invt T cell proliferation, indicating a role for autocrine IL-2 production in corticosteroid-mediated proliferative augmentation. Dexamethasone treatment of anti-CD3-stimulated V alpha 24invt T cells did not synergize with anti-Fas blockade in enhancing proliferation or preventing AICD. The V alpha 24invt T cell response to dexamethasone was dependent on the TCR signal strength. In the presence of dexamethasone, lower doses of anti-CD3 inhibited proliferation of V alpha 24invt T cells and CD4+ T cells; at higher doses of anti-CD3, which caused inhibition of CD4+ T cells, the V alpha 24invt T cell clones proliferated and were rescued from AICD. These results demonstrate significant differences in TCR signal strength required between V alpha 24invt T cells and CD4+ cells, and suggest important immunomodulatory consequences for endogenous and exogenous corticosteroids in immune responses.

Transcription of the Trypanosoma brucei spliced leader RNA gene is dependent only on the presence of upstream regulatory elements.

The spliced leader (SL) RNA plays a key role in mRNA maturation in trypanosomatid protozoa by providing the SL sequence, which is joined to the 5' end of every mRNA. As a first step towards a better understanding of the biogenesis and function of the SL RNA, we expressed a tagged SL RNA gene in a cell-free system of procyclic Trypanosoma brucei cells. Transcription initiates at + 1 can be detected as early as 1 min after addition of extract. Transcription of the SL RNA gene in vitro, as well as in permeable cells, is mediated by an alpha-amanitin/tagetitoxin resistant complex, suggesting a promoter that is intermediate between a classical RNA polymerase II and RNA polymerase III promoter. An analysis of the promoter architecture of the SL RNA gene revealed that regulatory elements are located upstream of the coding region and that the SL sequence, in contrast to the nematode SL sequence, is not required for T. brucei SL RNA gene transcription.

Dopamine synthesis in rat striatum: mobilization of tyrosine from non-dopaminergic cells.

Unilateral nigrostriatal lesions in rats that almost totally depleted striatal dopamine had no effect on striatal levels of dopamine's precursor, tyrosine, nor on those of leucine. Since prolonged electrical stimulation of the slices markedly depletes them of tyrosine (1,2) we conclude that tyrosine can be mobilized from non-dopaminergic striatal cells to augment dopamine release.

Effects of phenylalanine on the release of endogenous dopamine from rat striatal slices.

We examined the effect of phenylalanine (50-400 microM) on the electrically stimulated release of endogenous 3,4-dihydroxyphenylethylamine (dopamine or DA) from superfused rat striatal slices. In the absence of tyrosine, phenylalanine (25 microM) partially sustained DA release, but less well than an equimolar concentration of tyrosine. In the presence of tyrosine (50 microM), phenylalanine (in concentrations of greater than or equal to 200 microM) inhibited DA release into the superfusate. This inhibition was not associated with changes in tissue levels of tyrosine or DA, nor was it mimicked by addition of high concentrations of tyrosine or leucine to the medium. We conclude that phenylalanine is a less effective precursor of DA in rat striatum than tyrosine and that it can also act to inhibit DA synthesis, depending on its concentration.

Tyrosine availability determines stimulus-evoked dopamine release from rat striatal slices.

Direct evidence that precursor levels can affect catecholamine release from brain cells has not previously been presented. We observe a dose-dependent relationship between the tyrosine (Tyr) concentration of the superfusing medium and the amount of dopamine (DA) released from rat striatum by trains of electrical pulses. In the absence of exogenous tyrosine, tissue Tyr and DA levels are reduced following stimulation. These findings suggest that DA release from striatal neurons may not be sustained if fluctuations occur in the supply of Tyr to the brain.

Release of endogenous dopamine from electrically stimulated slices of rat striatum.

An experimental system is described for measuring the release of endogenous dopamine from electrically stimulated slices of rat striatum. Striatal slices were field-stimulated by two high frequency trains (S1 and S2) applied 10, 30 or 60 min apart. The quantities of dopamine released by the two stimuli were compared from slices incubated with and without dopamine's precursor, L-tyrosine. Sustained release of dopamine evoked by the two stimuli was shown to require the inclusion of tyrosine (50 microM) in the superfusate.

Interactions among the effects of normorphine, calcium and magnesium on transmitter release in the mouse vas deferens.

1 Excitatory junction potentials (e. j. ps) were recorded with intracellular electrodes from smooth muscle cells of the mouse vas deferens. 2 The dependence of the e.j.p. amplitude on the extracellular calcium ion concentration was determined in the absence or presence of normorphine (50 nM-1 microM) or magnesium (1.2-4.8 mM). 3 The interaction between normorphine and calcium was non-competitive beyond a dose-ratio of 1.5, whereas the interaction between magnesium and calcium was competitive up to the highest dose-ratio investigated (1.9). 4 It is suggested that inhibition by normorphine occurs at least partly by a mechanism different from that of magnesium.

Tetrahydroisoquinolines (TIQs) do not act on opiate receptors in the guinea-pig ileum.

The myenteric plexus-longitudinal muscle preparation of the guinea-pig ileum was stimulated with supra-maximal electrical field stimulation at 0.1 Hz. The contractile response was inhibited by salsolinol (1-300 microM) and tetrahydropapaveroline (THP) (3-30 micro M) but not by (cis)-3-carboxysalsolinol. S(-)-Salsolinol was more potent than R(+)-salsolinol. The inhibition by salsolinol and THP was unchanged by naloxone (up to 10 micro M). However, naloxone completely prevented the inhibition induced by normorphine, with a pA2 of 8.66. The results indicate that salsolinol and THP do not interact with opiate receptors in this preparation.