Prediction of heparin binding of mutated short sequences of rat thyroglobulin

BACKGROUND

Binding of thyroglobulin (Tg) to heparin is involved in Tg transcytosis via megalin. Rat Tg (rTg) binds to heparin through an exposed carboxyl terminal region (RELPSRRLKRPLPVK, Arg2489-Lys2503) rich in positively charged residues. This region is not entirely conserved in human Tg (hTg) (Arg2489-Glu2503, REPPARALKRSLWVE), resulting in lower affinity binding. Here, we developed a score to predict to what extent secondary structure modifications affect the heparin-binding ability of rTg.

METHODS

We designed eight synthetic peptides, including one with the Arg2489-Lys2503 sequence of rTg (rTgP), one with the corresponding sequence of hTg (hTgP), and six "mutant" peptides, each carrying a point mutation obtained by replacing one amino acid residue of rTgP with the corresponding residue of hTgP. Heparin binding was assessed in solid-phase assays. The Bmax and the constants of dissociation (K_d) were calculated.

RESULTS

Using a no-fee online service, we obtained predictions of peptide secondary structures and developed a scoring system to estimate to what extent mutations are expected to modify rTg secondary structure. The score was designated as Probability of Secondary Structure Change (PSSC) and it significantly correlated with the BMax (R = 0.942, P < 0.001) and the K_ds (R = - 0.744, P < 0.01) of heparin binding of hTgP and of the "mutant" peptides.

CONCLUSIONS

The PSSC score allows predicting to what extent point mutations are likely to affect the heparin-binding ability of short sequences of proteins: in this case rTg, regardless of whether mutations affect charge of the sequence. The secondary structure of Tg is likely to play a role in heparin binding.

Bulk and Surface Electronic Structure of the Dual-Topology Semimetal Pt_{2}HgSe_{3}

We report high-resolution angle-resolved photoemission measurements on single crystals of Pt_{2}HgSe_{3} grown by high-pressure synthesis. Our data reveal a gapped Dirac nodal line whose (001) projection separates the surface Brillouin zone in topological and trivial areas. In the nontrivial k-space range, we find surface states with multiple saddle points in the dispersion, resulting in two van Hove singularities in the surface density of states. Based on density-functional theory calculations, we identify these surface states as signatures of a topological crystalline state, which coexists with a weak topological phase.

Interleukin-17 and -22 synergy linking inflammation and EMT-dependent fibrosis in Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a chronic inflammatory, autoimmune and systemic disorder commonly associated with dry eyes and a dry mouth. Recently, the hypothetical link between epithelial-mesenchymal transition (EMT)-dependent salivary gland (SG) fibrosis and chronic inflammatory conditions has been suggested. In this study, we present data demonstrating a negative correlation of the epithelial marker E-cadherin expression and a positive correlation of mesenchymal vimentin and collagen type I expression with increasing degrees of tissue inflammation in pSS SG specimens. In addition, as it is not clear whether dysregulated cytokines in pSS, interleukin (IL)-17 and IL-22 may also contribute to the EMT-dependent fibrosis process, the effect of IL-17 and IL-22 treatment on EMT-dependent SG fibrosis was evaluated in primary human salivary gland epithelial cells (SGEC) isolated from healthy subjects. Here we present data demonstrating that IL-17 and IL-22 can induce SGEC to undergo a morphological and phenotypical transition to a mesenchymal phenotype. In support of this, vimentin and collagen type I were up-regulated while a decreased expression of E-cadherin occurs after interleukin treatment, and co-operation between IL-17 and Il-22 was required to induce the EMT.

Binding of thyroglobulin (Tg) to the low-density lipoprotein receptor-associated protein (RAP) during the biosynthetic pathway prevents premature Tg interactions with sortilin

OBJECTIVE

Sortilin, a Vps10p family member, is expressed by thyroid epithelial cells (TEC), where it binds to internalized thyroglobulin (Tg) molecules. Premature binding of Tg to sortilin during biosynthesis may cause intracellular retention of Tg. Such a premature interaction may be prevented by one or more inhibitor/s. Because both sortilin and Tg bind to the low-density lipoprotein receptor-associated protein (RAP), we investigated whether RAP serves such a function.

METHODS

Immunofluorescence staining for sortilin, Tg, and RAP was performed in FRTL-5 cells. Co-immunoprecipitation experiments were performed in extracts from FRTL-5 or COS-7 cells, the former co-transfected with Tg and/or RAP and/or sortilin, or in thyroid extracts from RAP KO mice.

RESULTS

Tg and sortilin did not co-localize in FRTL-5 cells following inhibition of protein synthesis, suggesting that newly synthesized, endogenous sortilin and Tg do not interact, in confirmation of which an anti-sortilin antibody did not co-precipitate Tg in FRTL-5 cells. In contrast, Tg co-localized with RAP in FRTL-5 cells. Co-immunoprecipitation of Tg with an anti-sortilin antibody in COS-7 cells transfected with sortilin and Tg was abolished when cells were co-transfected with RAP, indicating that RAP prevents binding of Tg to sortilin during biosynthesis, in confirmation of which an anti-sortilin antibody co-precipitated Tg in thyroid extracts from RAP KO mice to a greater extent than in thyroid extracts from WT mice.

CONCLUSIONS

Tg does not bind prematurely to sortilin because of its interaction with RAP during protein biosynthesis. These findings add new information to the knowledge of thyroid physiology.

Intracellular retention of thyroglobulin in the absence of the low-density lipoprotein receptor-associated protein (RAP) is likely due to premature binding to megalin in the biosynthetic pathway

OBJECTIVE

The low-density lipoprotein receptor associated protein (RAP) is expressed by thyroid epithelial cells (TEC) in a TSH-dependent manner. In the thyroid RAP functions as a molecular chaperone for the thyroglobulin (Tg) endocytic receptor megalin/LRP2, which is retained intracellularly in RAP KO mice rather than being expressed on the apical membrane of TEC, its usual location. RAP binds also to Tg, which is also retained intracellularly in RAP KO mice, thereby suggesting a role of RAP in Tg secretion. Here we investigated whether Tg intracellular retention in the absence of RAP is due to premature Tg-megalin interactions during the biosynthetic pathway or to a direct action of RAP on Tg secretion.

METHODS

We performed immunoprecipitation experiments in thyroid extracts from RAP KO and WT mice. In addition, we investigated Tg secretion in COS-7 cells co-transfected with human RAP (hRAP) and mouse Tg (mTg).

RESULTS

An anti-megalin megalin precipitated greater amounts of Tg in thyroid extracts from RAP KO than from WT mice, suggesting increased intracellular interactions between megalin and Tg in the absence of RAP. COS-7 cells transiently transfected with hRAP, mTg or both, expressed the two proteins accordingly. RAP was found almost exclusively in cell extracts, whereas Tg was found both in extracts and media, as expected from the knowledge that RAP is ER-resident and that Tg is secreted. Regardless of whether cells were transfected with mTg alone or were co-transfected with hRAP, similar proportions of the total Tg synthesized were detected in cell extracts and media.

CONCLUSIONS

The intracellular retention of Tg in the absence of RAP is likely due to its premature interaction with megalin, whereas RAP does not seem to affect Tg secretion directly.

Downstream activation of NF-κB in the EDA-A1/EDAR signalling in Sjögren's syndrome and its regulation by the ubiquitin-editing enzyme A20

Sjögren's syndrome (SS) is an autoimmune disease and the second most common chronic systemic rheumatic disorder. Prevalence of primary SS in the general population has been estimated to be approximately 1-3%, whereas secondary SS has been observed in 10-20% of patients with rheumatoid arthritis, systemic lupus erythematosus (SLE) and scleroderma. Despite this, its exact aetiology and pathogenesis are largely unexplored. Nuclear factor-kappa B (NF-κB) signalling mechanisms provide central controls in SS, but how these pathways intersect the pathological features of this disease is unclear. The ubiquitin-editing enzyme A20 (tumour necrosis factor-α-induced protein 3, TNFAIP3) serves as a critical inhibitor on NF-κB signalling. In humans, polymorphisms in the A20 gene or a deregulated expression of A20 are often associated with several inflammatory disorders, including SS. Because A20 controls the ectodysplasin-A1 (EDA-A1)/ectodysplasin receptor (EDAR) signalling negatively, and the deletion of A20 results in excessive EDA1-induced NF-κB signalling, this work investigates the expression levels of EDA-A1 and EDAR in SS human salivary glands epithelial cells (SGEC) and evaluates the hypothesis that SS SGEC-specific deregulation of A20 results in excessive EDA1-induced NF-κB signalling in SS. Our approach, which combines the use of siRNA-mediated gene silencing and quantitative pathway analysis, was used to elucidate the role of the A20 target gene in intracellular EDA-A1/EDAR/NF-κB pathway in SS SGEC, holding significant promise for compound selection in drug discovery.

Possible role of oral ibandronate administration in Osteonecrosis of the Jaw: a case report

We describe a case of Osteonecrosis of the Jaw (ONJ) that developed in a 65-year-old Caucasian woman with osteopenia and other risk factors who was receiving low doses of oral bisphosphonate therapy (ibandronate, 150 mg monthly). Computed tomography (CT), panoramic radiographs (OPT), 99mTc-Sn-MDP scintigraphy, and magnetic resonance imaging (MRI) were performed to study the diseased area; cytological examination also revealed the presence of suppurative material around the area of exposed bone. A diagnosis of bisphosphonate-related osteonecrosis of the jaw complicated by osteomyelitis was made. The patient was prescribed a drug protocol consisting of metronidazole 250 mg 2 times daily, chlorhexidine mouthwashes 3 times daily and chewing exercises for two months. Ibandronate was stopped and replaced with strontium ranelate. The symptoms improved and the patient is still under close follow-up. Assessment of the benefits versus risks is particularly necessary in patients with several risk factors to ascertain their eligibility for treatment with antiresorptive drugs and when this is not possible to choose alternative medications.

Absence of primary hypothyroidism and goiter in Slc26a4 (-/-) mice fed on a low iodine diet

BACKGROUND

Mutations in the SLC26A4 gene, coding for the anion transporter pendrin, are responsible for Pendred syndrome, characterized by congenital sensorineural deafness and dyshormonogenic goiter. The physiological role of pendrin in the thyroid is still unclear and the lack of a thyroid phenotype in some patients with SLC26A4 mutations and in Slc26a4 (-/-) mice indicate the existence of environmental or individual modifiers able to compensate for pendrin inactivation in the thyroid. Since pendrin can transport iodide in vitro, variations in iodide supply have been claimed to account for the thyroid phenotype associated with pendrin defects.

AIM

The Slc26a4 (-/-) mouse model was used to test the hypothesis that iodide supply may influence the penetrance and expressivity of SLC26A4 mutations.

MATERIALS AND METHODS

Slc26a4 (-/-) and (+/+) mice were fed up to 6 months on a standard or low iodine diet and were evaluated for thyroid structural abnormalities or biochemical hypothyroidism.

RESULTS

A 27-fold iodide restriction induced similar modifications in thyroid histology, but no differences in thyroid size, T4 or TSH levels were observed between between Slc26a4 (-/-) and (+/+) mice, either in standard conditions and during iodine restriction.

CONCLUSIONS

Iodide restriction is not able to induce a thyroid phenotype in Slc26a4 (-/-) mice. These experimental data, together with those coming from a review of familial Pendred cases leaving in regions either with low or sufficient iodide supply, support the idea that the expression of thyroid phenotype in Pendred syndrome is more powerfully influenced by individual factors than by dietary iodide.

Quercetin decreases proliferation of orbital fibroblasts and their release of hyaluronic acid

BACKGROUND

Inhibition of fibroblast (FB) proliferation and hyaluronic acid (HA) production may be a therapeutic approach to Graves' ophthalmopathy (GO). The flavonoid quercetin has a wide range of activities, including reduction of FB growth.

AIM

To investigate the effects of quercetin in orbital FB from GO patients and control subjects.

METHODS

Primary cultures of orbital FB were treated with quercetin or with its glycosides rutin and quercitrin. Cell proliferation, necrosis, apoptosis, HA production, and cell cycle were measured.

RESULTS

Beginning at a 30 μM concentration, quercetin, but not rutin and quercitrin, reduced cell proliferation, with no difference between GO and control FB. The effect of quercetin on proliferation was due to necrosis and cell cycle blockade, whereas apoptosis was unaffected. Quercetin reduced HA in the cell media, with no difference between GO and control FB.

CONCLUSIONS

Quercetin reduces cell proliferation and HA release in orbital FB. Whether these initial findings have any potential for the use of quercetin in the clinical practice remains to be established.

Binding, uptake, and degradation of internalized thyroglobulin in cultured thyroid and non-thyroid cells

Thyroid hormone release requires degradation of thyroglobulin (Tg) by thyroid epithelial cells, which occurs mainly in the lysosomal pathway following Tg endocytosis. Non-specific fluid-phase endocytosis is thought to be the main route of Tg uptake leading to degradation, whereas receptor- mediated endocytosis is believed to lead to post-endocytic pathways other than degradation. To gain more insights into these issues, we investigated handling of Tg by various cell types. Tg bound similarly to thyroid (FRTL-5, FRT) and non-thyroid (COS-7, IRPT) cells, indicating the presence of membrane-binding sites, presumably receptors, in both cell types. Tg was internalized and degraded by all cells and degradation paralleled uptake, with the exception of FRTL- 5 cells, in which a lower proportion of Tg was degraded, suggesting that in FRTL-5 cells mechanisms that target Tg to the various post-endocytic pathways (either receptors or postreceptorial factors) are differently represented. Immunoelectronmicroscopy showed a common path of endocytosis in FRTL-5, COS-7, and IRPT cells, namely the formation of pseudopods engulfing Tg, followed by internalization and accumulation of Tg in cytoplasmic vesicles and lysosomes. The fastest rate was observed in COS-7 cells, probably reflecting a lower impact of endocytic receptors. Our findings suggest that Tg uptake and degradation are not thyroid-specific, that Tg binding sites exist in different cell types, and that uptake and/or degradation are differently regulated in differentiated thyroid cells, presumably because of a different impact of endocytic receptors or post-endocytic mechanisms, which are probably responsible for the regulation of hormone release.

Anti-Ro/SSA autoantibody-mediated regulation of extracellular matrix fibulins in human epithelial cells of the salivary gland

OBJECTIVES

The fibulins are a family of extracellular matrix (ECM) molecules that regulate the organ shape along with other growth factors and stromal cells and have recently been shown to be involved in a variety of cellular functions including proliferation, migration, differentiation, and survival. Important changes in acinar and ductal morphology and function, together with pronounced ECM remodelling, are detectable in the labial salivary glands (LSGs) of patients with Sjögren's syndrome (SS). Here we report the in vitro expression of the recently identified ECM proteins fibulin-6 and fibulin-7 by human salivary gland epithelial cells (SGECs). The ability of anti-Ro/SSA autoantibodies (Abs) to modulate fibulin-6 and fibulin-7 expression was investigated.

METHODS

Semiquantitative reverse transcription polymerase chain reaction (RT-PCR) and real-time PCR were used to analyse fibulin-6 and fibulin-7 mRNA expression. Confocal microscopy and fluorescence-activated cell sorting (FACS) were used to study expression of the proteins in primary human SGEC cultures, established from biopsies of minor LSGs, in both untreated control cells and anti-Ro/SSA Abs-treated cells.

RESULTS

The methods used show the expression of fibulin-6 and fibulin-7 in SGECs. Treatment of cells with anti-Ro/SSA Abs results in a down-regulation of fibulin-6 mRNA expression whereas no significant differences were observed in fibulin-7 expression between untreated and treated cells.

CONCLUSION

Dysregulation of fibulin expression in SGECs by anti-Ro/SSA Abs may contribute to disorganization of the ECM environment and thus cause injury to the salivary gland architecture and functionality observed in SS.

Structural Similarities Between mRNA for the Formyl Peptide Receptors and 18S rRNA

Formyl peptides released by some bacteria are powerful chemoattractants and activators of mammalian granulocytes and monocytes, acting through 7-transmembrane specific formyl peptide receptors (FPRs). Three distinct segments of the formyl peptide receptor 1 (FPR1) mRNA of Man share probabilistically significant homologies with segments of the 18S rRNA which are highly conserved from Drosophila to Man. Overall, the three segments cover approximately 24% that of the 18S rRNA sequence and approximately 36% of the FPR1 sequence. The three segments are, however, arranged in different orders in the 18S rRNAs and in the FPR1 mRNA, the segment appearing in the first location in the 18S rRNAs is located at the end of the FPR1 mRNA sequence. The hypothesis is advanced that the three "conserved" segments either derive from an ancestral gene that is the forerunner of both the ribosomal 18S genes and the FPR genes or that at some stage of evolution the FPR genes derived, at least in part, from the more ancient ribosomal 18S genes. The extant 18S rRNA sequences exhibit obvious signs of a number of breaks that occurred during evolution, especially in the transition from insects to vertebrates. Some of these events may have resulted in differential rearrangements of segments in the groups of FPR genes and ribosomal 18S genes.

Formyl Peptide Receptor Expression in Birds

N-formyl-methionyl-leucyl-phenylalanine (fMLP) is a major chemotactic factor produced by Escherichia coli and other Gram-negative bacteria. The prototypal human fMLP receptor 1 (FPR1) was cloned in 1990 from a differentiated HL-60 myeloid leukemia cell cDNA library. In transfected cells, FPR1 binds fMLP with high affinity and is activated by picomolar to low nanomolar concentrations of fMLP in chemotaxis and calcium ion mobilization assays. Two additional human genes, designated FPR-like 1 (FPRL1) and FPR-like 2 (FPRL2), were later isolated by low-stringency hybridization using FPR1 cDNA as a probe, and these were shown to cluster with FPR1 on chromosome 19q13.3. In avian models the fMLP effects and the possible expression of FPRs have been poorly investigated. In this study we demonstrated that stimulation with fMLP of cultured cells isolated from the 10-day chick embryo brain causes superoxide anion and nitric oxide release and protein phosphorylation at serine, threonine, and tyrosine residues. These effects were abrogated by pretreatment with pertussis toxin, suggesting the involvement of a G-protein-coupled receptor (GPCR). Although specific N-formyl peptide receptors have so far been demonstrated only in mammals, a specific polyclonal antihuman-FPR1 antibody proved to bind to the membrane of both neurons and glial cells isolated from the chick brain. Immunoblot analysis revealed a single band corresponding to 60 kDa ca. A BLAST search and aa sequence alignments demonstrated that a number of avian 7-transmembrane (7TM) GPCRs share some homologies with the human FPR1. Furthermore, the CXCR4 ligand, SDF-1alpha, seems to compete with the antihuman-FPR1 polyclonal antibody used in our experiments. We thus advance the hypothesis that in birds one (or more) of the expressed 7TM GPCRs, most probably chemokine receptors belonging to the CXCR4 subfamily, also may act as fMLP receptors.

Chemokine CXC Receptor 4: An Evolutionary Approach

Selected segments of the nucleotide sequences of the human 18S rRNA and the human formyl peptide receptor 1 mRNA exhibit structural similarities that are unlikely to be due simply to chance. Herein we analyze the structural similarities between the human 18S rRNA gene and the vertebrate chemokine CXC receptor 4 (CXCR4) gene that encodes a class A (rhodopsin-like) seven-transmembrane G-protein coupled receptor belonging to the same superfamily of formyl peptide receptors. The method of study was based on the recording of the positions of the 7-or-more-base oligonucleotide identities encountered in the 18S and CXCR4 genes and the construction of scatter-plots (abscissa-18S; ordinate-CXCR4) displaying the identity points positions. Analysis of the distribution of distances between identity points (abscissa-ordinate in the scatter-plot) demonstrated distinct peaks of frequency around 1200. Series of identities arranged near diagonal lines at 45 degrees in the scatter-plot (quasialignments) were evaluated for their probabilistic level of random occurrence. Results of this analysis demonstrated nonrandom quasialignments between (i) a 900-nt ca. section of the human CXCR4 intron that immediately precedes almost the whole of the coding sequence and the 18S gene from nt 125 to 1025 ca.; and (ii) a 425-nt ca. section of the CXCR4 vertebrate genes, corresponding to nt 137-560 of the coding sequence, and the 18S gene from nt 1300 to 1730 ca. In both instances significant quasialignments are evidenced when CXCR4 nt sequences are shifted to the right by about 1200 nt with respect to the 18S nt sequence, as confirmed by analysis of the abscissa - ordinate differences. Taken together, these results indicate that, at least in humans, a continuous nonrandom quasialignment extends for some 1600 nt, from the second part of the (single) intron to the first part of the coding sequence. We hypothesize that the relatively more recent CXCR4 vertebrate gene might be evolutionarily related to the more ancient and highly conserved 18S gene.

Polimorphonuclear Cell-Mediated Oxidative Stress: Sink for Reactive Oxygen Species and Cell Various Type Damage

Reactive oxygen species (ROS) are produced in animals and humans under physiologic and pathologic conditions. Polymorphonuclear cells (PMNs) and other professional phagocytes are able to generate large amounts of ROS that have not only antimicrobial capacity but are also deleterious to mammalian cells and responsible for many chronic diseases. In particular, ROS produced in large amounts by the massively infiltrating leukocytes in inflammed tissues are believed to constitute a major tissue-destructive force and may contribute significantly to the pathogenesis of several inflammatory diseases. Inflammation can accelerate the development of cancer: in fact, it seems that a part of the predisposition to cancer may be attributed to the oxidants released by the phagocytes at inflammatory site and then to the effects of continuous damage over a life span by ROS. The focus of this study was to investigate the differential capacity of ROS capture and the relative cellular damage degree in gastric, intestinal and fibroblastic cell lines. These various cell types were in vitro used as sink for ROS released by co-cultured fMLP-stimulated human polymorphonuclear cells. Our data demonstrated that cell lines showed a differential capacity of ROS capture correlated to cellular damage, probably due to a different cell susceptibilty to the oxidative challenge produced by stimulated PMNs.

Selective TNF-ALPHA Gene Silencing Attenuates Apoptosis in Human Salivary Gland Epithelial Cells

RNA interference (RNAi) was used in this study for selective knockdown of TNF-alpha gene expression in anti-Ro/SSA autoantibodies (Abs)-treated human salivary gland epithelial cells. Our findings reveal that selective TNF-alpha gene silencing resulted in the subsequent attenuation of the pro-apoptotic effects of anti-Ro/SSA Abs; this could have therapeutic effects in autoimmune diseases.

Hashimoto's thyroiditis in Melkersson-Rosenthal syndrome patient: casual association or related diseases?

Melkersson-Rosenthal syndrome (MRS) is a rare disorder of unknown etiology. MRS is classically defined as a triad of recurrent orofacial edema, relapsing paralysis of the facial nerve, and fissured tongue. The authors present the case of a 52-year-old woman with orofacial swelling and facial pain attacks. The patient reported to suffer of hypothyroidism and laboratory findings disclosed free triiodothyronine (FT(3)), free thyroxine (FT(4)), and thyrotropin (TSH) altered. Endocrinological consult led to the diagnosis of Hashimoto's thyroiditis. Antithyroper-oxidase antibodies (anti-TPO) were highly elevated and thyroid function tests had evidenced a clinically significant hypothyroidism. A link between MRS and immunological disorders such as sarcoidosis, Crohn's disease, unilateral anterior uveitis and multiple sclerosis was documented. The literature did not report any association between Hashimoto's thyroiditis and Melkersson-Rosenthal syndrome. The presence of the anti-TPO antibodies in the case reported here could suggest a possible correlation between immunological alteration characteristic of autoimmune thyroiditis and MRS.

Kidney abnormalities in low density lipoprotein receptor associated protein knockout mice

Mice lacking the LDL receptor associated protein (RAP) have a severe defect of thyroglobulin secretion into the colloid, associated with moderately increased serum TSH levels and histological features of early goiter. RAP is expressed also in renal proximal tubule cells, where it functions as a molecular chaperone for the endocytic receptor megalin, which is responsible for reabsorption of low molecular weight proteins from the glomerular filtrate. Here we investigated whether the thyroid phenotype in RAP knockout (KO) mice is associated with kidney alterations. By immunohistochemistry, we found that in RAP KO mice megalin expression on the apical membrane of renal proximal tubule cells was markedly reduced, with intracellular retention of the receptor. The reduced expression of megalin was associated with its impaired function. Thus, urinary protein concentrations and urinary protein excretion in 24 h were higher in RAP KO than in wild-type mice. Coomassie staining of urine samples revealed an increased intensity of low molecular mass bands in the urine of RAP KO mice, indicating that they had low molecular weight proteinuria. Therefore, we concluded that disruption of the RAP gene determines not only thyroid abnormalities, but also a severe defect of megalin expression and function in the kidney.

Sequencing of the entire coding region of the receptor associated protein (RAP) in patients with primary hypothyroidism of unknown origin

The LDL receptor-associated protein (RAP) is involved in secretion of thyroglobulin (Tg) from the thyrocyte to the colloid. Disruption of the RAP gene in mice results in a reduced Tg content within the colloid, leading to subclinical hypothyroidism and histological alterations resembling early goiter. Here we studied the entire coding sequence of RAP in genomic DNA samples from 18 patients with primary hypothyroidism not due to thyroid autoimmunity or dysgenesis. The control group included 21 subjects with no evidence of thyroid alterations. Eleven different polymorphisms with amino-acid substitution and 4 different missense polymorphisms without amino-acid substitution were found in various regions of the RAP gene. Only one polymorphism in exone 7 (V311M) was observed exclusively in patients, but it had been previously reported in normal subjects as well. The remaining polymorphisms were found either both in patients and controls or only in controls and had not been previously reported. The frequency of the various polymorphisms did not differ significantly between patients and controls. Based on these findings, we conclude that alterations of the RAP gene are not a common cause of hypothyroidism, although it cannot be excluded that other, rarer alterations with a pathogenic effect exist, and that they should be investigated in a larger number of patients.

Formyl peptide receptors on immune and nonimmune cells: analysis of sequence conservation in FPR genes

Formyl peptides are oligopeptides released by Gram-negative bacteria. So far, specific formyl peptide receptors (FPRs) have been described in mammals only. FPRs are seven-transmembrane G-coupled molecules and make up a relatively homogeneous group, although exhibiting different levels of affinity for the ligands. We examined the patterns of conservation/mutation within the FPR group of genes, as studied in 16 mRNAs from different species. Following alignment of the coding sections, those nucleotides identical in at least 15 sequences were assigned a "conservation index" 2; those with 8-14 identities an index 1; those with less than 8 identities an index zero. The cumulative average conservation index was 1.36. The autocorrelation function and the power spectrum of the whole series of indexes demonstrated a 3-unit periodicity. This periodicity is explained by the fact that the average conservation indexes of the first, second and third nucleotides of the coding triplets were 1.46, 1.55 (both above the mean), and 1.06 (below the mean), respectively, so that correlations at lag 3 tend to be all positive. In mRNAs, regardless of the position in the coding triplets, T is significantly more frequently conserved (average index = 1.60) than A, C, and G (1.21 - 1.38). In the nucleotides with conservation index 1 or zero, we recorded the two more frequently represented bases. In 35% of mRNA nucleotides the two more frequently represented bases were C and T; in 28% of cases the two more frequently represented bases were A and G; other couples occurred with lower frequencies. Both mutations may arise following C methylation with subsequent transformation into T (by deamination), either in the template or the coding DNA strand. Thus, we hypothesized that in FPR mRNAs there is an evolutionary trend of transformation from G to A and from C to T, the latter being the more stable of the bases.

Modeling of granulocyte cytoskeletal responses following fMLP challenging

Formyl peptides released from Gram-negative bacteria ligate a group of specific mammalian receptors, expressed mainly on granulocytes, monocytes, and macrophages. Receptor ligation activates different transduction cascades, eventually leading to the release of reactive oxygen species and other bactericidal chemical species, and the activation of the actin cytoskeleton with extension of lamellipodia and migration toward the sites of maximal formyl peptide concentration. In vitro, under conditions of nongradient formyl peptide concentrations, lamellipodia form all around the cell contour (chemokinesis). In granulocytes challenged under these conditions with N-formyl-methionyl-leucyl-phenylalanine, (i) the power spectrum of the contour of activated cells shows a peak at a specific periodicity, indicating that the lamellipodial extension is not completely random but stochastically conforms to a deterministic scheme, and (ii) the morphological response (percent of cells exhibiting chemokinesis) tends to reach a maximum at certain drug concentrations, then declining at higher concentrations. Accordingly, the logarithm of the drug concentration-polarizing effect curve is bell-shaped. Herein we illustrate theoretical models for the simulation of these two components of the chemokinetic responses. We show that the main traits of the general morphology and arrangement of lamellipodia may be simulated by an algorithm that starting from a situation of random distribution of active receptors on the cell membrane, encompasses in the successive calculation cycles both a local autocatalytic enhancement of the actin polymerization and a relative inhibition of the actin polymerization at some distance from the more active polymerization foci. In addition, a drug log concentration-polarizing effect bell-shaped curve may be simulated by assuming that the N-formyl-methionyl-leucyl-phenylalanine, while binding with high affinity to the specific receptor, is also able to bind to another lower affinity receptor that may effect depolarizing actions or, more generally, metabolic blocking effects. Under these conditions, at low drug concentrations the polarizing effect brought about by the ligation of the specific receptor is largely predominant. However, as the drug concentration increases and the specific receptors approach saturation, the inhibitory effects become more and more powerful and the net polarizing effect is reduced.

Siögren's syndrome: anti-Ro and anti-La autoantibodies trigger apoptotic mechanism in the human salivary gland cell line, A-253

AIM

The Sjögren's syndrome (SS) is an autoimmune rheumatic disease that targets salivary and lacrimal glands, characterized by a high concentration of autoantibodies in the serum. The anti-Ro and anti-La autoantibodies are present in approximately 70-90% of the patients with primary SS and this presence is correlated to extraglandular manifestations. The objective of this work was to explore the cellular apoptotic pathway triggered by binding and penetration of anti-Ro and anti-La autoantibodies, isolated from the total IgG fraction of patients with primary SS, in the human salivary gland cell line A-253.

METHODS

The sera were obtained from 13 healthy volunteers and 13 patients with primary SS. The IgG was obtained from sera through precipitation with ammonium sulfate and the anti-La and anti-Ro autoantibodies were purified using Sepharose 4B-Ro and Sepharose 4B-La affinity columns. The methods used to evaluate the apoptosis were: DNA fragmentation, immunofluorescence and immunoenzymatic tests.

RESULTS

In the salivary gland cells, the anti-Ro and anti-La autoantibodies: 1) are able to penetrate; 2) induce DNA fragmentation and cleavage and activation of the effector caspase-3. In the same experimental condition, IgG purified from healthy sera did not have any apoptotic effect on the human salivary gland cell line.

CONCLUSION

Anti-Ro and anti-La autoantibodies mediate the apoptosis the human salivary gland cells A-253 in a caspase-3 dependent manner.

Anti-Ro and anti-La autoantibodies induce TNF-alpha production by human salivary gland cells: an in vitro study

In this report, we demonstrate that both TNFR1 and the TNFR2 are expressed on the salivary gland cell line A-253 cell membrane. Furthermore, cell treatment with anti-Ro and anti-La autoantibodies from Sjögren IgG determined TNF-alpha production, clarifying which could be the inducer of the extrinsic pathway of apoptosis in salivary gland cells.

Evaluation of barriers to clinical trial enrollment through a novel pharmacy quality assurance tool

17026

Background: Clinical trials offer the best treatment for patients with cancer, yet less than 5 percent of adults and less than 60 percent of children are enrolled on clinical trials. To determine reasons for lack of enrollment on clinical trials and to assess areas for potential trial development, we designed a ‘non-protocol’ form for use at our center. Our goal was to assess deficiencies in our menu of trials, identify other barriers to enrollment, and to indirectly increase awareness of trials. Methods: Completion of a ‘non-protocol’ form was required by the pharmacy with the first set of new chemotherapy orders for all Cancer Institute of New Jersey ambulatory patients who were not enrolled on a clinical trial. The form required completion of one of three areas for lack of enrollment: trial availability, reason for ineligibility, or other reason for not enrolling the patient. Results: From June 2003 through December 2005, 474 forms were collected for patients not enrolled on a clinical trial. The median age of patients not enrolled on trial was 56 years (range 1 to 88 years) and females outnumbered males (69% vs 31%). Lack of trial availability limited enrollment for 51% of patients (n=241) while administration of standard therapy was listed for 10 patients. Of those patients where a trial was available (n=223), 65% (n=145) of patients were not eligible, most commonly due to performance status (n=55). The remaining 78 patients refused participation. To determine if implementation of this pharmacy service changed the reasons for lack of enrollment, the data was evaluated by year: Conclusion: Lack of trial availability has been a rate-limiting factor in enrollment on clinical trials at our center. The data generated from the implementation of this novel pharmacy service is of strategic importance to the center. It is reviewed with the tumor-focused groups of the cancer center to identify areas for developing clinical trials.

[Table: see text]

No significant financial relationships to disclose.

Comparison of the demographics of patients enrolled (E) versus those not enrolled (NE) on therapeutic clinical trials at a comprehensive cancer center

17065

Background: In the U.S., representation of minorities and the elderly in clinical trials has been low yet few reports have evaluated this potential barrier to enrollment by comparing the demographics of patients E vs NE within an institution. Therefore, we compared these groups to determine if there were significant differences in demographics at our center. Methods: For all E patients, demographic data is collected in a clinical trial database. For evaluated NE patients, data was captured through a ‘non-protocol’ form. A univariate analysis was performed on the demographic data, including gender, age, race, and insurance status, for each year to determine if there were differences in patients E vs NE on a therapeutic clinical trial. Results: From June 2003 through December 2005, there were 912 E patients and data available on 474 NE patients. The results were consistent for each year from 2003 to 2005, and therefore combinable, with no statistical difference in any parameter for E patients versus NE patients during any year with the exception of gender (p=0.05; Chi-square). The distribution of patients E by gender is 52% (474/912) female vs 48% (438/912) male and NE is 69% (325/474) female vs 31% (149/474) male. The mean age of E patients was 55 vs 56 years for NE patients, with 32% vs 33% representing those >65years, respectively. For the E patients, 84% were white, 7.2% black, 4.6% Asian, 4.2% unknown, and 0.4% Hawaiian/Pacific Islander (H/PI). For the NE patients, where race was not consistently available, 65% were white, 9.3% black, 3.2% Asian, 20.5% unknown, and 2.1% H/PI. In both groups, most patients had private insurance (E 60%, NE 54%), followed by Medicare (E 27.5%, NE 29%), Medicaid (E 4%, NE 9%), self pay (E 7.5%, NE 7.4%), and unknown (E 1.3%, NE 0.4%). Conclusions: When comparing E vs NE patients, gender was the only factor that differed significantly. Although this result suggests that males were more likely to be E in a clinical trial, this finding should be interpreted with caution, since this difference might relate to differences in trial availability. While lower enrollment rates for the elderly and minority patients have been identified nationally, enrolling this group of patients does not appear to be a barrier at our center.

No significant financial relationships to disclose.

Medication safety in cancer clinical trials: An analysis of medication error reports at a comprehensive cancer center

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Background: Although medication errors comprise 10–25% of all medical errors, little is known concerning the occurrence or types of medication errors occurring while treating patients on a clinical trial. Therefore, we retrospectively reviewed the medication errors reported in patients enrolled on clinical trials at our center. Methods: As part of a multidisciplinary continuous quality improvement project, from January 2003 through December 2006, we collected voluntary reports of medication errors in adult and pediatric patients on clinical trials involving both oral and intravenous chemotherapy. All reports were classified prospectively regarding clinical trial involvement, severity category (A to I) per the National Coordination Council on Medical Error Reporting and Prevention, type, cause, and where in the medication use process the error occurred. Results: There were 163 reports involving patients treated on clinical trials. The most common errors were those corrected prior to reaching the patient in 68% of events (Category A&B), while 31% reached the patient but did not result in harm (Category C&D), with 1% resulting in temporary patient harm (Category E&F). The most common type of errors were prescribing (66%), improper dose (42%), and omission errors (9%). Not following an institutional procedure or the protocol was the primary cause for these errors (39%), followed by the written order (30%), and poor communication involving both the healthcare team and the patient (26%). The processes where the errors initiated were in prescribing 47%, administration 10%, dispensing 6%, and monitoring 5%. Conclusion: Medication errors do occur in clinical trials, however the majority of these are corrected prior to reaching the patient or do not result in harm. Not following an institutional procedure or the protocol was the most common cause of error. This is most likely due to the protocol procedures differing from existing standards of care. Protocol-specific education through the Centralized Education and Training Service, a shared resource within our cancer center, addresses this issue enhancing the quality and safety of clinical trials through the education and training of healthcare professionals.

No significant financial relationships to disclose.

The 18S rRNA is basically composed of two tandem quasirepeats. Insights into the evolution of some innate immunity receptors

The gene encoding the 18S rRNA is an ancient molecule and its basic structure has been highly conserved from fish to mammals. Recently, we compared the nucleotide sequences of the human 18S rRNA and the human formyl peptide receptor 1 mRNA and concluded that selected segments of the two sequences exhibit similarities that are unlikely to be due simply to chance. Other data suggest the existence of nonrandom similarities between the 18S rRNA and the chemokine CXC receptor 4 mRNA. Therefore we advance the hypothesis that some groups of genes encoding 7-transmembrane G-coupled receptors of immunological interest may be evolutionarily related to the 18S gene. In this article we analyze the base-sequence architecture of the human 18S rRNA in terms of similarities between selected segments within the molecule. The method of study was based on the recording of the positions of 7- to 11-base oligonucleotide repeats, followed by a probabilistic analysis of the random occurrence of the repeats. Herein we show that most of the 18S rRNA molecule appears to be composed of two long tandem quasirepeats. We hypothesize that an ancestral gene structure composed of a chain of about 850 nucleotides duplicated to form a two-unit tandem repeat. Then the two units diverged as a consequence of independent nucleotide mutations, deletions, and insertions, but still retaining recognizable homologies. In addition, further nonduplicated shorter segments were added to build up the complete sequence.

Evolution of a “Conserved” Amino Acid Sequence: a Model Study of an In Silico Investigation of the Phylogenesis of Some Immune Receptors

In this paper we analyze a 55-amino acid (aa) sequence which is relatively well conserved in several seven-transmembrane receptor families (from Insects to Mammals) and in some Viruses. This sequence, which covers the second transmembrane domain, the first extracellular loop and the third transmembrane domain, appears in its complete configuration in most of the seven-transmembrane receptor families, as well as in the protein products of some viruses. Other seven-transmembrane receptors and viruses exhibit reduced configurations of the conserved sequence, lacking either aa 31 or aa 30-31. 53-aa configurations are typically found in most chemokine receptor (CKR) subfamilies, as well as in some viral protein products. However, the CCR1, CCR3, and CCR6 subfamilies comprise a 54-aa configuration and the CKR-related protein products, ChemR23 and RDC1, include the complete 55-aa sequence. For each CKR subfamily the "modal sequence" of the conserved segment was constructed by selecting the most frequently occurring aa at each position. Then, pairwise alignments were made between: (i) the modal CKR sequences, and (ii) the sequence (53-aa) of the Yaba-like disease virus - 7L protein. From the alignments two consensus matrices were derived: (i) the consensus 1 matrix with reference to the whole conserved segment, and (ii) the consensus 2 matrix with reference to aa 22-29, which appear to be the most variable segment of the sequence. Based on the obtained consensus values and with reference to this specific conserved segment, the following conclusions are proposed: (1) ChemR23 and RDC1 are probably the more primitive CKR forms; (2) CCR1 and CCR3 may be grouped in a single cluster; (3) CCRs 2, 4, and 5 are closely related to each other and may be grouped in a cluster; CCR7 is likely to be evolutionarily related to this cluster; (4) CXCRs 2, 3, and 4 and CCX CKR appear to be evolutionarily related to each other and very likely derived from an CCR6-like gene; (5) CCR2/4/5 and CCR7 may have derived either from CCR1/3-like or CCR6-like genes; (6). The Yaba-like disease virus--7L protein most likely derived, through "molecular piracy", from a CCR8-like gene. We also discuss possible, more remote, evolutionary links between CKRs, formylpeptide receptors, and possibly the highly conserved 18S rRNA genes.

Biological role of the N-formyl peptide receptors

Ligation of N-formyl-methionyl-leucyl-phenylalanine (fMLP) to its specific cell surface receptors triggers different cascades of biochemical events, eventually leading to cellular activation. The formyl peptide receptors (FPRs) are members of the seven-transmembrane, G-protein coupled receptors superfamily, expressed at high levels on polymorphonuclear and mononuclear phagocytes. The main responses elicited upon ligation of formylated peptides, referred to as cellular activation, are those of morphological polarization, locomotion, production of reactive-oxygen species and release of proteolytic enzymes. FPRs have in recent years been shown to be expressed also in several non myelocytic populations, suggesting other unidentified functions for this receptor family, independent of the inflammatory response. Finally, a number of ligands acting as exogenous or host-derived agonists for FPRs, as well as ligands acting as FPRs antagonists, have been described, indicating that these receptors may be differentially modulated by distinct molecules.

Autoantibodies from Sjögren's syndrome induce activation of both the intrinsic and extrinsic apoptotic pathways in human salivary gland cell line A-253

Sjögren's syndrome (SS) is an autoimmune rheumatic disease that targets salivary and lachrymal glands, characterized by a high concentration of serum autoantibodies directed against nuclear and cytoplasmic antigens. It is known that autoantibodies can enter viable cells and this phenomenon has functional consequences including activation of apoptotic process. The objective of this work was to explore whether autoantibodies contained in IgG purified from Sjögren sera trigger apoptotic process in an experimental model represented by the human salivary gland cell line A-253. To define if the intrinsic or extrinsic pathways are activated, we examined which caspases are critical for inducing cell death. The results have demonstrated that morphological changes and DNA laddering, consistent with apoptotic cell death, occurred in A-253 cells treated with IgG from Sjögren sera. Sjögren IgG induced cleavage and activation of the effector caspase-3 and degradation of the caspase-3 substrate poly(ADP-ribose)polymerase. Both the intrinsic and extrinsic apoptotic pathways were activated, since both caspase-8 and caspase-9 cleavages occurred. In conclusion, autoantibodies contained in IgG purified from Sjögren sera mediate apoptosis of the A-253 cell line in a caspase-dependent manner.

Poorly specific binding of thyroglobulin to orbital fibroblasts from patients with Graves' ophthalmopathy

It has been proposed that thyroglobulin (Tg) may be involved in the pathogenesis or the progression of Graves' ophthalmopathy (GO). According to this hypothesis, following its release from the thyroid, Tg would reach orbital tissues, thereby eliciting an autoimmune aggression. In support of this, we recently found that intact Tg is present in orbital tissues of patients with GO, where it is complexed with glycosaminoglycans. In this study, we searched for additional Tg binding sites in orbital tissues, using primary cultures of orbital and skin fibroblasts from 7 GO patients who had undergone orbital decompression. Biotin-labeled Tg bound to both skin and orbital fibroblasts in a saturable manner, with constants of dissociation of approximately 75 nmol/l for skin fibroblasts and approximately 40 nmol/I for orbital fibroblasts. In an attempt to identify Tg binding sites, fibroblast extracts were blotted onto membranes that were incubated with biotin-labeled Tg, which bound especially to a protein migrating at approximately 300 kDa, present in both orbital and skin fibroblast extracts. Because no appreciable inhibition of binding of biotin-labeled Tg was produced by unlabeled Tg, we concluded that binding was poorly specific and it is unlikely to be involved in the pathogenesis of GO.

Reduced expression of the chemokine receptor CCR1 in human macrophages and U-937 cells in vitro infected with Leishmania infantum

Chemokines exert their actions through G-proteinlinked receptors, which are expressed to variable extents by different cell types. In accordance with the chemokine classification, these receptors are designated as CXC, CC, XC, and CX(3)C, followed by R and a number. The purpose of this investigation was to evaluate CCR1 expression in human peripheral blood-derived macrophages and the human monocytic U-937 cell line. Cells in vitro were infected with live Leishmania infantum promastigotes (zymodeme MON1); cell lysates were then subjected to SDS-PAGE and immunoblotting, by using an anti-CCR1 affinity purified polyclonal antibody. The expression of the CCR1 gene was analyzed by RT-PCR, using specific human primers. The results of both immunoblotting and RT-PCR showed that CCR1 expression in Leishmania-infected cells was lower than in uninfected control cells. These results indicate that Leishmania infantum infection causes a down-regulation of the CCR1 gene and protein expression, suggesting that reduced phagocyte recruitment at the inflammation sites could favor parasite progression and the spread of Leishmania infection.

Failure to use measurement of megalin secretory components complexed with serum thyroglobulin as a tool to identify metastases after surgery in papillary thyroid cancer

When thyroid follicles are intact, some colloidal thyroglobulin (Tg) reaches the circulation by megalin-mediated transcytosis and is to various extents complexed with megalin secretory components. In contrast, in papillary thyroid cancer (PTC), serum Tg is not complexed with megalin because it is directly secreted by tumor cells. Here we attempted to use measurement of megalin secretory components to distinguish PTC patients with thyroid remnant plus metastases from those with thyroid remnant only, after thyroidectomy and before 131I ablation. Tg values in anti-Tg antibodies (TgAb)-free sera from 5 PTC patients with thyroid remnant plus metastases and 12 PTC patients with thyroid remnant only were measured following pre-adsorption with uncoupled protein A beads or with protein A beads coupled with antimegalin antibodies. The degree of Tg pre-adsorption with antimegalin antibodies was minimal, with no substantial differences between the two groups. Thus, we concluded that measurement of megalin secretory components is unlikely to be useful to identify the origin of serum Tg in PTC patients after thyroidectomy.

Role of thyroglobulin in the pathogenesis of Graves' ophthalmopathy: the hypothesis of Kriss revisited

One of the hypothesis to explain the pathogenesis of Graves' ophthalmopathy (GO) was formulated by Joseph P. Kriss in the early 1970s. He postulated that the initiating event in the pathogenesis of GO is the deposition and accumulation of thyroglobulin (Tg) in orbital tissues, followed by an autoimmune reaction against Tg. In the last 30 yrs several studies have addressed this hypothesis, through various, different experimental approaches, raising results that are both in favor and against the possibility that Tg plays a role in the pathogenesis of GO. The finding that intact Tg is present in orbital tissues of GO patients supports Kriss' hypothesis, although the role of Tg as an autoantigen seems to be unlikely, as GO is not significantly associated with serum TgAb and mice immunized with Tg do not develop GO. Whether Tg is indeed involved in the pathogenesis of GO remains to be established. Our current view is that, provided that Tg plays a role, it is unlikely the only factor involved and Tg in orbital tissues may rather reinforce or worsen a damage initiated by other mechanisms.

Tooth morphogenesis and pattern of odontoblast differentiation

The terminal differentiation of odontoblasts is controlled by the inner dental epithelium (IDE) and occurs according to a tooth-specific pattern. It requires temporospatially regulated epigenetic signaling and the expression of specific competence. The patterning of cusp formation was compared with that of odontoblast differentiation in the first lower molar in mice. Histology, immunostaining, and three dimensional reconstructions were completed by experimental approaches in vitro. The mesenchyme controls the pattern of cusp formation. During the cap-bell transition in the molar, a subpopulation of nondividing IDE cells from the enamel knot (EK) undergo a tooth-specific segregation in as many subpopulations as cusps will form. Epithelial cell-basement membrane interactions seem to be involved in the segregation of EK cells. The timing and spatial pattern of the segregation of EK cells correlate with cusps formation. However, the temporal pattern of odontoblast terminal differentiation is different. This discrepancy might result from cusp-specific differences either in the timing of the initiation of odontoblast terminal differentiation and/or in cell proliferation kinetics.

Impaired thyroglobulin (Tg) secretion by FRTL-5 cells transfected with soluble receptor associated protein (RAP): evidence for a role of RAP in the Tg biosynthetic pathway

Secretion of thyroglobulin (Tg) by thyrocytes requires several endoplasmic reticulum (ER)-resident molecular chaperones. The receptor-associated protein (RAP), a known molecular chaperone, binds to Tg in thyroid cells shortly after biosynthesis. Here we investigated whether RAP is involved in Tg secretion by FRTL-5 cells. For this purpose, we studied Tg secretion by FRTL-5 cells transfected with a soluble RAP chimera, as a mean for interfering with endogenous RAP. We used a RAP-human IgG Fc (RAP-Ig) chimeric cDNA, which was designed in order to exclude the ER retention sequence of RAP and to allow generation of a secreted form of RAP. FRTL-5 cells were transiently transfected with the RAP-Ig cDNA or, as control, with a CD8-Ig cDNA. Media were collected at 24, 48 and 72 h after transfection. Secretion of fusion proteins and of Tg in the media was measured by ELISA. As expected, under standard culture conditions, RAP was not secreted into the media by FRTL-5 cells, even though it could be detected by Western blotting in cell extracts. In transfection experiments, fusion proteins were present in the media of FRTL-5 cells transfected with either RAP-Ig or CD8-Ig, indicating that transfection was successful. Although Tg was found in the media of FRTL-5 cells transfected with either CD8-Ig or RAP-Ig, a lower amount was found in cells transfected with RAP-Ig. Therefore, we concluded that RAP is involved in Tg secretion by FRTL-5 cells suggesting that RAP may function as a Tg molecular chaperone.

Postnatal lower jaw dentition in different phenotypes of tabby mice

The tabby (Ta) syndrome in mouse is homologous to human anhidrotic ectodermal dysplasia, including defective development of hair, teeth, and glands. To complete the available data on the functional dentition in the Ta mice, we analyzed the mandibular cheek teeth in 261 postnatal specimens arranged in several phenotype/genotype groups: 51 Ta-hemizygous males, 56 Ta-homo/hemizygous females, 64 Ta-heterozygous females, and 40 and 50 wild-type control males and females, respectively. We evaluated tooth number, size, shape and eruption and compared these parameters in the different groups. In any individual group of Ta mice, there was variability mainly in the size and shape of the most mesial tooth and in the tooth patterns. The incidence of a reduction in tooth number in homozygous and hemizygous mice was dependent on the breeding scheme.

Targeting of thyroglobulin to transcytosis following megalin-mediated endocytosis: evidence for a preferential pH-independent pathway

TG internalized from the colloid by megalin, bypasses the lysosomal pathway and is transported across thyrocytes by transcytosis. Although most of the intracellular mechanisms responsible for targeting of ligands to transcytosis are unknown, for certain ligands a role of lysosomal pH has been established. Thus, ligands that undergo lysosomal degradation dissociate from their receptors due to the low pH of endosomes, whereas certain ligands that undergo transcytosis fail to dissociate because they bind to their receptors at acidic pH. Here we studied the role of pH in TG transcytosis. We first investigated the effect of pH on megalin binding to TG in solid phase assays and found that, although megalin bound to TG at various pH values (ranging from 4-8), optimal binding was seen at acidic pH (ranging from 4.5-6). We then studied the effect of chloroquine (CQ) and ammonium chloride (AC), which increase endosomal pH, on transcytosis of TG across Fisher rat thyroid (FRTL-5 cells). Transcytosis assays were performed using FRTL-5 cells cultured on filters in dual chambered devices, with megalin expression only on the upper surface of the layers. TG was added to the upper chamber and transcytosed TG was measured in fluids collected from the lower chamber after incubation at 37 C. Treatment of FRTL-5 cells with CQ or AC did not affect binding and uptake of TG, but it did reduce T3 release from exogenously added TG, used as a measure of TG degradation in the lysosomal pathway. Treatment with CQ or AC resulted in an increase of transcytosis of TG across FRTL-5 cells, but only to a minimal extent (15-20%). The effects of CQ or AC and those of a megalin competitor (the monoclonal antibody 1H2, which reduced transcytosis) were not additive, suggesting that CQ and AC act on the megalin-mediated pathway. In conclusion, because TG binding to megalin is greatest at acidic pH, it is possible that TG does not dissociate from megalin in the lysosomal pathway. However, the pH-dependence of TG binding to megalin does not account for much of transcytosis, which probably occurs largely because of other mechanisms of targeting.

[Effect of the Tabby mutation on the dentition of mice]

The X-linked hypohidrotic ectodermal dysplasia in man leads to dental defects and is homologous to the Tabby (Ta) mutation in mouse. We currently investigate the effects of the Ta mutation on odontogenesis. The incisor germ of Ta showed an abnormal size and shape, a change in the balance between prospective crown- and root-analogue tissues and retarded cytodifferentiation. Although the enamel organ in Ta incisors was smaller, a larger proportion of the dental papilla was covered by preameloblasts-ameloblasts. The independent development of the labial and lingual parts of the enamel organ in rodent lower incisor might reflect their heterogeneous origin, as demonstrated for the upper incisor. The mandibular cheek dentition in Ta mice exhibits large variations classified in five morphotypes, based on the tooth number, shape, size and position. In Ta embryos, the mesio-distal extent of the dental epithelium was similar to that in WT, but its segmentation was altered. These morphotypes could be explained by a tentative model suggesting that 1) the positions of tooth boundaries differ in Ta and WT molars and among the Ta morphotypes; 2) the tooth patterns are determined by the distal boundary of the most mesial tooth primordium while the distal teeth take advantage of the remaining dental epithelium; 3) one tooth primordium in Ta mice might derive from adjacent parts of two primordia in WT.

Different morphotypes of the tabby (EDA) dentition in the mouse mandible result from a defect in the mesio-distal segmentation of dental epithelium

OBJECTIVES

Prenatal identification of the different dentition morphotypes, which exist in the lower molar region of tabby (Ta) adult mice, and investigation of their origin. The mouse Ta syndrome and its counterpart anhidrotic (hypohidrotic) ectodermal dysplasia (EDA) in human are characterized by absence or hypoplasia of sweat glands, hair and teeth.

DESIGN

Analysis of tooth morphogenesis using serial histological sections and 3D computer aided reconstructions of the dental epithelium in the cheek region of the mandible.

SETTING AND SAMPLE POPULATION

Institute of Experimental Medicine, Academy of Sciences, Prague. Heads of 75 Ta homozygous and hemizygous mice and 40 wild type (WT) control mice aged from embryonic day (ED) 14.0-20.5 (newborns), harvested during 1995-2001.

OUTCOME MEASURE

Prenatal identification of five distinct morphotypes of Ta dentition on the basis of differences in tooth number, size, shape, position and developmental stage and of the morphology of the enamel knot in the most mesial tooth primordium.

RESULTS

The mesio-distal length of the dental epithelium was similar in the lower cheek region in Ta and WT mice. In Ta embryos, there was altered the mesio-distal segmentation of the dental epithelium giving rise to the individual tooth primordia. Prenatally, two basic morphotypes I and II and their particular subtypes (Ia, Ib, Ic, and IIa, IIb, respectively) of the developing dentition were identified from day 15.5. The incidence of the distinct morphotypes in the present sample did not differ from postnatal data. The proportion of the morphotype I and II was dependent on mother genotype.

CONCLUSION

The different dentition morphotypes in Ta mice originate from a defect in the mesio-distal segmentation of the dental epithelium in mouse embryos. This defect presumably leads to variable positions of tooth boundaries that do not correspond to those of the WT molars. One tooth primordium of Ta mice might be derived from adjacent parts of two molar primordia in WT mice.

Different morphotypes of functional dentition in the lower molar region of tabby (EDA) mice

OBJECTIVES

To sort and classify the highly variable lower molar dentition in tabby (Ta) mice postnatally. The Ta syndome is homologous to the anhidrotic (hypohidrotic) ectodermal dysplasia (EDA) in human and includes severe developmental defects of teeth, hair and sweat glands.

DESIGN

Analysis of tooth shape and cusp pattern and measurement of the mesio-distal crown length.

SETTING AND SAMPLE POPULATION

Institute of Experimental Medicine, Academy of Sciences, Prague. Fixed heads of 107 tabby (Ta) homozygous and hemizygous mice and 90 wild type mice aged from post-natal day 11 to adulthood, collected during 1995-2001.

OUTCOME MEASURE

Identification of distinct morphotypes of Ta dentition. Reduced tooth length in Ta teeth and specific differences in tooth length between distinct morphotypes.

RESULTS

The variable dentitions in the lower molar region of Ta mice were classified in two basic morphotypes I and II. The morphotype I was further subdivided into particular morphotypes Ia, Ib and Ic. Proportion of the basic morphotypes I and II was different in the offspring of heterozygous (84% and 12%) compared with homozygous + hemizygous (45% and 52%) mothers. The proportions of particular morphotypes within a basic morphotype were similar in both offspring groups.

CONCLUSION

The identification of the distinct morphotypes made possible to classify the structural variability of the mandibular functional dentition in Ta mice.

Crown morphology and pattern of odontoblast differentiation in lower molars of tabby mice

The Tabby mutation leads to abnormal crown morphology in the developing molars. To identify cusps which were altered in number, size, and position in the first lower molars of mutant mice, we analyzed the patterning of odontoblast differentiation using morphological criteria on serial sections and 3D reconstructions. In wildtype mice, polarized and functional odontoblasts were first observed in the median L2 and B2 cusps, then in the distal cusps L3 and B3, and finally in L1, B1, and 4. In Tabby mice, terminal differentiation of odontoblasts was retarded by 24-36 hours compared with wild-type mice. Polarized odontoblasts first appeared in the most mesial part of the tooth and progressively extended distally. The mesial part of the M1 in Tabby fetuses may correspond to the L2, B2 area from wild-type mice. The ante-molar dental primordium observed in some samples would thus represent remnants of cusps L1 and B1.

Binding of the low density lipoprotein receptor-associated protein (RAP) to thyroglobulin (Tg): putative role of RAP in the Tg secretory pathway

The 39-44 kDa protein known as the receptor-associated protein binds to members of the low density lipoprotein receptor family and is found within cells that express these receptors. The receptor-associated protein has been shown to prevent premature binding of ligands to the receptors in the endoplasmic reticulum and to promote proper folding and transport of the receptors in the secretory pathway. In the thyroid, megalin (a low-density lipoprotein receptor family member) serves as an endocytic receptor for thyroglobulin. Here we present evidence that the receptor-associated protein can bind to thyroglobulin, which suggests a novel function of the receptor-associated protein, namely binding of certain megalin ligands possibly during the biosynthetic pathway. In solid-phase assays thyroglobulin was shown to bind to the receptor-associated protein with moderately high affinity (mean between K(d) and K(i) = 39.8 nM), in a calcium-dependent and saturable manner. The receptor-associated protein also bound to a native carboxyl-terminal 230-kDa thyroglobulin polypeptide, which markedly reduced binding of intact thyroglobulin to the receptor associated protein, indicating that the receptor-associated protein binding sites of thyroglobulin are located in the carboxyl-terminal portion of the molecule. In addition to thyroglobulin, the receptor-associated protein specifically bound to another megalin ligand, namely lipoprotein lipase. Because lipoprotein lipase markedly reduced receptor-associated protein binding to thyroglobulin, we concluded that the receptor-associated protein uses the same binding site/s to bind to thyroglobulin and lipoprotein lipase. Evidence of thyroglobulin binding to the receptor-associated protein was also obtained in vivo and in cultured thyroid cells. Thus, anti-receptor-associated protein antibodies precipitated intact thyroglobulin from extracts prepared from rat thyroids and cultured thyroid cells (FRTL-5 cells). Chase experiments after inhibition of protein synthesis in FRTL-5 cells showed that thyroglobulin interacts with the receptor-associated protein shortly after the beginning of thyroglobulin biosynthesis.