Genetic variants of PARP4 gene and PARP4P2 pseudogene in patients with multiple primary tumors including thyroid cancer.

Recently, the PARP4 gene has been identified as a possible susceptibility gene of primary thyroid and breast cancers. We analyzed PARP4 in 53 patients with multiple primary cancers including a thyroid cancer (TC), in 74 patients with TC alone, and in 88 healthy donors. Two PARP4 intronic variants within the IVS29 (c.3543 + 44T > C) and the IVS22 (c.2758 + 9G > A) were found only in the two patient groups. Moreover, we found a rare variant (r.522C > A) within a PARP4 pseudogene (PARP4P2) in one patient with four primary tumors, and with a familial cancer history. PARP4 mRNA was absent in all primary tumors and matched normal tissues, whereas the pseudogene variant transcript was always expressed. Consistently, immunostaining for PARP4 protein was negative at nuclear level in all tissues, thus suggesting that PARP4P2 pseudogene variant could alter its regulatory role on PARP4, inducing the down-regulation of PARP4 expression at both tumor and normal tissues level. In conclusion, germline intronic PARP4 variants could be a risk factor for the development of TC, and PARP4P2 pseudogene variations associated with PARP4 down-regulation may confer susceptibility to develop multiple metachronous cancers.

Impact of Mutation Density and Heterogeneity on Papillary Thyroid Cancer Clinical Features and Remission Probability.

BACKGROUND: The need to integrate the classification of cancer with information on the genetic pattern has emerged in recent years for several tumors. METHODS: The genomic background of a large series of 208 papillary thyroid cancers (PTC) followed at a single center was analyzed by a custom MassARRAY genotyping platform, which allows the simultaneous detection of 19 common genetic alterations, including point mutations and fusions. RESULTS: Of the PTCs investigated, 71% were found to have pathognomonic genetic findings, with BRAFV600E and TERT promoter mutations being the most frequent monoallelic alterations (42% and 23.5%, respectively), followed by RET/PTC fusions. In 19.2% of cases, two or more point mutations were found, and the co-occurrence of a fusion with one or more point mutation(s) was also observed. Coexisting BRAFV600E and TERT promoter mutations were detected in a subgroup of aggressive PTCs (12%). A correlation between several aggressive features and mutation density was found, regardless of the type of association (i.e., only point mutations, or point mutations and fusions). Importantly, Kaplan-Meier curves demonstrated that mutation density significantly correlated with a higher risk of persistent disease. In most cases, the evaluation of the allelic frequencies normalized for the cancer cell content indicated the presence of the monoallelic mutation in virtually all tumor cells. A minority of cases was found to harbor low allelic frequencies, consistent with the presence of the mutations in a small subset of cancer cells, thus indicating tumor heterogeneity. Consistently, the presence of coexisting genetic alterations with different allelic frequencies in some tumors suggests that PTC can be formed by clones/subclones with different mutational profiles. CONCLUSIONS: A large mono-institutional series of PTCs was fully genotyped by means of a cost- and time-effective customized panel, revealing a strong impact of mutation density and genetic heterogeneity on the clinical features and on disease outcomes, indicating that an accurate risk stratification of thyroid cancer cannot rely on the analysis of a single genetic event. Finally, the heterogeneity found in some tumors warrants attention, since the occurrence of this phenomenon is likely to affect response to targeted therapies.

Transcriptional profiling of human bronchial epithelial cell BEAS-2B exposed to diesel and biomass ultrafine particles.

BACKGROUND: Emissions from diesel vehicles and biomass burning are the principal sources of primary ultrafine particles (UFP). The exposure to UFP has been associated to cardiovascular and pulmonary diseases, including lung cancer. Although many aspects of the toxicology of ambient particulate matter (PM) have been unraveled, the molecular mechanisms activated in human cells by the exposure to UFP are still poorly understood. Here, we present an RNA-seq time-course experiment (five time point after single dose exposure) used to investigate the differential and temporal changes induced in the gene expression of human bronchial epithelial cells (BEAS-2B) by the exposure to UFP generated from diesel and biomass combustion. A combination of different bioinformatics tools (EdgeR, next-maSigPro and reactome FI app-Cytoscape and prioritization strategies) facilitated the analyses the temporal transcriptional pattern, functional gene set enrichment and gene networks related to cellular response to UFP particles. RESULTS: The bioinformatics analysis of transcriptional data reveals that the two different UFP induce, since the earliest time points, different transcriptional dynamics resulting in the activation of specific genes. The functional enrichment of differentially expressed genes indicates that the exposure to diesel UFP induces the activation of genes involved in TNFα signaling via NF-kB and inflammatory response, and hypoxia. Conversely, the exposure to ultrafine particles from biomass determines less distinct modifications of the gene expression profiles. Diesel UFP exposure induces the secretion of biomarkers associated to inflammation (CCXL2, EPGN, GREM1, IL1A, IL1B, IL6, IL24, EREG, VEGF) and transcription factors (as NFE2L2, MAFF, HES1, FOSL1, TGIF1) relevant for cardiovascular and lung disease. By means of network reconstruction, four genes (STAT3, HIF1a, NFKB1, KRAS) have emerged as major regulators of transcriptional response of bronchial epithelial cells exposed to diesel exhaust. CONCLUSIONS: Overall, this work highlights modifications of the transcriptional landscape in human bronchial cells exposed to UFP and sheds new lights on possible mechanisms by means of which UFP acts as a carcinogen and harmful factor for human health.

MassARRAY-based simultaneous detection of hotspot somatic mutations and recurrent fusion genes in papillary thyroid carcinoma: the PTC-MA assay.

PURPOSE: We exploited the MassARRAY (MA) genotyping platform to develop the "PTC-MA assay", which allows the simultaneous detection of 13 hotspot mutations, in the BRAF, KRAS, NRAS, HRAS, TERT, AKT1, PIK3CA, and EIF1AX genes, and six recurrent genetic rearrangements, involving the RET and TRK genes in papillary thyroid cancer (PTC). METHODS: The assay was developed using DNA and cDNA from 12 frozen and 11 formalin-fixed paraffin embedded samples from 23 PTC cases, together with positive and negative controls. RESULTS: The PTC-MA assay displays high sensitivity towards point mutations and gene rearrangements, detecting their presence at frequencies as low as 5%. Moreover, this technique allows quantification of the mutated alleles identified at each tested locus. CONCLUSIONS: The PTC-MA assay is a novel MA test, which is able to detect fusion genes generated by genomic rearrangements concomitantly with the analysis of hotspot point mutations, thus allowing the evaluation of key diagnostic, prognostic, and therapeutic markers of PTC in a single experiment without any informatics analysis. As the assay is sensitive, robust, easily achievable, and affordable, it is suitable for the diagnostic practice. Finally, the PTC-MA assay can be easily implemented and updated by adding novel genetic markers, according to clinical requirements.

Letter regarding the article: "Multiple HABP2 variants in familial papillary thyroid carcinoma: Contribution of a group of "thyroid-checked" controls" by Kern et al.

This Journal recently published a study (Kern et al., 2017) reporting the genetic analysis of the whole HABP2 gene in 11 independent kindreds with familial non medullary thyroid cancer (FNMTC). The Authors showed that a new variant (p.R122W) displayed a minor allele frequency (MAF) significantly higher in FNMTC patients than in controls (7.5 vs 0.73%, p = 0.016) and cosegregated with thyroid cancer in one kindred, thus suggesting the need for the evaluation of its possible pathogenicity in other series. We thus analyzed this new HABP2 p.R122W variant in our wide series of 32 unrelated FNMTC Italian kindreds. The variant was not found in any of the 72 affected and 12 not affected family members. In conclusion, the HABP2R122W was not found in our wide series and it is thus unlikely to be causal to FNMTC. We therefore suggest that careful replication studies should be performed when assessing the possible association between FNMTC risk and any HABP2 variant.

Segregation and expression analyses of hyaluronan-binding protein 2 (HABP2): insights from a large series of familial non-medullary thyroid cancers and literature review.

INTRODUCTION: Recently, the G534E variant of the HABP2 gene was reported as the underlying genetic defect in a large kindred with nonsyndromic familial nonmedullary thyroid cancer (FNMTC). Nevertheless, this postulated role was not confirmed in additional cohorts. Contrasting data are also available on HABP2 expression in the thyroid. OBJECTIVES: To investigate HABP2 as a potential susceptibility gene in a large series of 27 unrelated families with FNMTC and to test its expression in thyroid tumour and matched normal tissues. RESULTS: Three of the 27 FNMTC families (11·1%) carried the HABP2G534E variant. The genotyping of these families showed that HABP2G534E does not segregate with cancer. Indeed, affected individuals not carrying HABP2G534E were identified, and the variant was present also in members without thyroid cancer. HABP2 mRNA had a very variable expression in tissues from FNMTC, sporadic papillary thyroid cancers (PTCs) or contralateral normal tissues, by either nonquantitative or quantitative RT-polymerase chain reaction. In almost all cases, the gene appeared down- or up-regulated in tumours with respect to the corresponding normal tissue. At immunohistochemistry, HABP2 was expressed in both tumour and matched control tissues, without differences between sporadic and familial cases. CONCLUSIONS: This study on a wide series of FNMTC indicates that the HABP2G534E variant is frequent, but does not segregate with the disease. Nevertheless, the dysregulation of HABP2 expression found in either sporadic or familial PTCs or normal thyroid tissues is consistent with similar findings in other malignancies and could indicate a role of this gene also in thyroid cancer.

Integrative transcriptomic and protein analysis of human bronchial BEAS-2B exposed to seasonal urban particulate matter.

BACKGROUND: Exposure to particulate matter (PM) is associated with various health effects. Physico-chemical properties influence the toxicological impact of PM, nonetheless the mechanisms underlying PM-induced effects are not completely understood. OBJECTIVES: Human bronchial epithelial cells were used to analyse the pathways activated after exposure to summer and winter urban PM and to identify possible markers of exposure. METHODS: BEAS-2B cells were exposed for 24 h to 10 µg/cm(2) of winter PM2.5 (wPM) and summer PM10 (sPM) sampled in Milan. A microarray technology was used to profile the cells gene expression. Genes and microRNAs were analyzed by bioinformatics technique to identify pathways involved in cellular responses. Selected genes and pathways were validated at protein level (western blot, membrane protein arrays and ELISA). RESULTS: The molecular networks activated by the two PM evidenced a correlation among oxidative stress, inflammation and DNA damage responses. sPM induced the release of pro-inflammatory mediators, although miR-146a and genes related to inflammation resulted up-regulated by both PM. Moreover both PM affected a set of genes, proteins and miRNAs related to antioxidant responses, cancer development, extracellular matrix remodeling and cytoskeleton organization, while miR-29c, implicated in epigenetic modification, resulted up-regulated only by wPM. sPM effects may be related to biological and inorganic components, while wPM apparently related to the high content of organic compounds. CONCLUSIONS: These results may be helpful for the individuation of biomarkers for PM exposure, linked to the specific PM physico-chemical properties.

Whole genome SNP genotyping and exome sequencing reveal novel genetic variants and putative causative genes in congenital hyperinsulinism.

Congenital hyperinsulinism of infancy (CHI) is a rare disorder characterized by severe hypoglycemia due to inappropriate insulin secretion. The genetic causes of CHI have been found in genes regulating insulin secretion from pancreatic ß-cells; recessive inactivating mutations in the ABCC8 and KCNJ11 genes represent the most common events. Despite the advances in understanding the molecular pathogenesis of CHI, specific genetic determinants in about 50 % of the CHI patients remain unknown, suggesting additional locus heterogeneity. In order to search for novel loci contributing to the pathogenesis of CHI, we combined a family-based association study, using the transmission disequilibrium test on 17 CHI patients lacking mutations in ABCC8/KCNJ11, with a whole-exome sequencing analysis performed on 10 probands. This strategy allowed the identification of the potential causative mutations in genes implicated in the regulation of insulin secretion such as transmembrane proteins (CACNA1A, KCNH6, KCNJ10, NOTCH2, RYR3, SCN8A, TRPV3, TRPC5), cytosolic (ACACB, CAMK2D, CDKAL1, GNAS, NOS2, PDE4C, PIK3R3) and mitochondrial enzymes (PC, SLC24A6), and in four genes (CSMD1, SLC37A3, SULF1, TLL1) suggested by TDT family-based association study. Moreover, the exome-sequencing approach resulted to be an efficient diagnostic tool for CHI, allowing the identification of mutations in three causative CHI genes (ABCC8, GLUD1, and HNF1A) in four out of 10 patients. Overall, the present study should be considered as a starting point to design further investigations: our results might indeed contribute to meta-analysis studies, aimed at the identification/confirmation of novel causative or modifier genes.

Genetic analysis of Italian patients with congenital hyperinsulinism of infancy.

BACKGROUND/AIMS: Congenital hyperinsulinism of infancy is a rare disease that needs prompt treatment to avoid brain damage. There are currently no data regarding the clinical and molecular features of Italian patients. METHODS: Thirty-three patients with HI and their parents were included. Consanguinity was reported in six patients. Half of patients were macrosomic at birth. None had raised 3-hydroxybutyrylcarnitine or hyperammonemia. Molecular analysis of ABCC8 and KCNJ11 genes was performed in all patients, and subjects with no mutation underwent analysis of HNF4A and GCK. GLUD1 and HADH genes were analyzed in a patient with leucine sensitivity. RESULTS: Mutations in the ABCC8 and KCNJ11 genes were found in 45% of the patients (6 novel). No mutations in HNF4A, GLUD1 and GCK genes were found. Recessive mode of inheritance was found in 21% of patients. A single heterozygous mutation was identified in 24% of probands. 72% of the patients were responsive to medical treatment, and 44% of the 17 patients with no identified mutation achieved spontaneous remission. Nine children, unresponsive to medical therapy, underwent pancreatectomy. CONCLUSION: This is the first report on hyperinsulinism of infancy in Italy, confirming the complexity of the clinical forms and the heterogeneity of the genetic causes of the disease.

Gene expression profiling of A549 cells exposed to Milan PM2.5.

BACKGROUND: Particulate matter (PM) has been associated to adverse health effects in exposed population and DNA damage has been extensively reported in in vitro systems exposed to fine PM (PM2.5). The ability to induce gene expression profile modulation, production of reactive oxygen species (ROS) and strand breaks to DNA molecules has been investigated in A549 cells exposed to winter and summer Milan PM2.5. RESULTS: A549 cells, exposed to 10 µg/cm(2) of both winter and summer PM2.5, showed increased cytotoxicity at 24h and a significant increase of ROS at 3h of treatment. Despite these similar effects winter PM induced a higher number of gene modulation in comparison with summer PM. Both PMs modulated genes related to the response to xenobiotic stimuli (CYP1A1, CYP1B1, TIPARP, ALDH1A3, AHRR) and to the cell-cell signalling (GREM1) pathways with winter PM2.5 inducing higher fold increases. Moreover the winter fraction modulated also JUN (cell-cell signalling), GDF15, SIPA1L2 (signal transduction), and HMOX1 (oxidative stress). Two genes, epiregulin (EREG) and FOS-like antigen1 (FOSL1), were significantly up-regulated by summer PM2.5. The results obtained with the microarray approach have been confirmed by qPCR and by the analysis of CYP1B1 expression. Comet assay evidenced that winter PM2.5 induced more DNA strand breaks than the summer one. CONCLUSION: Winter PM2.5 is able to induce gene expression alteration, ROS production and DNA damage. These effects are likely to be related to the CYP enzyme activation in response to the polycyclic aromatic hydrocarbons (PAHs) adsorbed on particle surface.

Identification of a diffuse form of hyperinsulinemic hypoglycemia by 18-fluoro-L-3,4 dihydroxyphenylalanine positron emission tomography/CT in a patient carrying a novel mutation of the HADH gene.

OBJECTIVE: Congenital hyperinsulinism is the most common cause of persistent hypoglycemia in infancy (HI), leading to severe neurologic disabilities if not promptly treated. The recent application of positron emission tomography (PET)/computed tomography (CT) scanning with 18-fluoro-l-3,4 dihydroxyphenylalanine improved the ability to distinguish the two histopathologic forms of HI (focal and diffuse), whose differentiation heavily influences the therapeutic management of the patient. CASE REPORT: We describe the case of a patient presenting with severe hypoglycemia from infancy. High concentration of insulin suggested the diagnosis of congenital hyperinsulinism. No metabolic disorders related to amino acid, organic acids or fatty acid oxidation were detected. Medical treatment was able to obtain a satisfactory metabolic response. RESULTS: The patient underwent PET/CT scanning, revealing a diffuse form of the disease. The absence of mutations in KCNJ11 and ABCC8 genes (responsible for 50% of HI cases), and whole genome single nucleotide polymorphisms analysis by microarray suggested the HADH gene as a likely candidate. Sequence analysis revealed a novel homozygous nonsense mutation (R236X) in HADH gene. CONCLUSIONS: This case indicates that mutations of the HADH gene should be sought in hyperinsulinemic patients in whom diffuse form of HI and autosomal recessive inheritance can be presumed when KCNJ11 and ABCC8 genes mutational screening is negative, even in the absence of altered organic acids and acylcarnitines concentration.

Identification of two novel frameshift mutations in the KCNJ11 gene in two Italian patients affected by Congenital Hyperinsulinism of Infancy.

Congenital Hyperinsulinism of Infancy (CHI) is a genetically heterogeneous disorder characterized by profound hypoglycemia related to inappropriate insulin secretion. Two histopathologically and genetically distinct groups are recognized among patients with CHI due to ATP-sensitive potassium channel (KATP) defects: a diffuse type (Di-CHI), which involves the whole pancreas, and a focal form (Fo-CHI), which shows adenomatous islet-cell hyperplasia of a particular area within the normal pancreas. The beta-cell KATP channel consists of two essential subunits: Kir6.2 encoded by the KCNJ11 gene which is the pore-forming unit and belongs to the inwardly rectifying potassium channel family, and SUR1 (sulfonylurea receptor 1) encoded by the ABCC8 gene, which belongs to the ATP-binding cassette (ABC) transporter family. The KATP channel is an octameric complex of four Kir6.2 and four SUR1 subunits. More than one hundred mutations have been found in KATP channel genes ABCC8 and KCNJ11, but to date only twenty mutations have been identified in KCNJ11, most of them are missense mutations and only one is a single base deletion. The Fo-CHI has been demonstrated to arise in individuals who have a germline mutation in the paternal allele of ABCC8 or KCNJ11 in addition to a somatic loss of the maternally derived chromosome region 11p15 in adenomatous pancreatic beta-cells, while Di-CHI predominantly arises from the autosomal recessive inheritance of KATP channel gene mutations. Here we describe the molecular findings in nine children who presented, in the neonatal period, with signs and symptoms of hypoglycemia and diagnosed affected by CHI according to international diagnostic criteria. Direct sequencing of the complete coding exon and promoter region of KCNJ11 gene showed, in two Italian patients, two new heterozygous mutations which result in the appearance of premature translation termination codons resulting in the premature end of Kir6.2. Interestingly most of the CHI mutations detected in other population studies are situated in the ABCC8 gene.

RNA-mediated interference indicates that SEL1L plays a role in pancreatic beta-cell growth.

The specificity of SEL1L expression and promoter activity for the pancreatic cell population, its chromosomal location, as well as its similarities to the yeast Hrd3p protein, a component of HRD complex which is responsible for endoplasmic reticulum (ER)-associated degradation of numerous ER-resident proteins, prompted us to study its effects on beta cell function. In this study we show that lowering SEL1L expression, by using the short interfering RNAs technology as well as antisense transfection, resulted in severe perturbation of betaTC-3 growth and metabolic activity. We hypothesize that SEL1L may exert its function by protecting the cells from ER stress and could counteract immune responses.

Autosomal dominant hypocalcemia in monozygotic twins caused by a de novo germline mutation near the amino-terminus of the human calcium receptor.

UNLABELLED: To define the molecular pathogenesis of severe postnatal hypocalcemia in monozygotic twin sisters, we sequenced their CaR gene and identified a missense mutation, K29E. Expression of the mutant receptor in vitro showed a marked increase in Ca2+ sensitivity explaining the observed phenotype. Additional mutagenesis studies lead us to speculate concerning a novel mechanism whereby the K29E mutation may lead to receptor activation. INTRODUCTION: Activating mutations of the Ca(2+)-sensing receptor (CaR) gene have been identified in subjects with autosomal dominant hypocalcemia. Study of such mutations has provided insight into the mechanism of activation of the CaR. MATERIALS AND METHODS: We performed biochemical and molecular genetic studies on monozygotic twin sisters who presented with early postnatal hypocalcemia and on their unaffected sister and parents. Functional characterization of mutant CaRs transfected in HEK-293 cells included immunoblots to monitor protein expression and Ca2+ stimulation of phosphoinositide hydrolysis to measure Ca2+ sensitivity. RESULTS: We identified a K29E missense mutation in the twin sisters but not in their parents or unaffected sister. The K29E mutant CaR showed a marked increase in Ca2+ sensitivity, including when it was co-transfected with wildtype CaR cDNA, consistent with a dominant effect. Substitution of K29 by aspartate equivalently increased CaR sensitivity, whereas conservative substitution by arginine did not. CONCLUSIONS: Severe postnatal hypocalcemia in the twin sisters was caused by a de novo germline activating mutation. In a model of the Venus flytrap-like domain of the extracellular amino-terminus of the CaR, K29 is located close to a peptide loop, "loop 2," that forms part of the dimer interface and is the site of 10 of the previously reported naturally occurring activating CaR mutations. We speculate that K29E increases Ca2+ sensitivity of the CaR by disrupting a salt bridge between K29 and an acidic residue in loop 2 and thereby changes the normal structure of loop 2 that maintains the CaR in its inactive conformation.

Longitudinal changes in bone metabolism and bone mineral content in children with celiac disease during consumption of a gluten-free diet.

BACKGROUND: A gluten-free diet (GFD) rapidly corrects the bone mineral deficit of children with untreated celiac disease. The mechanisms underlying such changes are still poorly understood. OBJECTIVE: In a longitudinal study, we monitored changes in bone metabolism during consumption of a GFD. DESIGN: We studied 22 white patients with celiac disease (11 girls) aged 10.5 +/- 1.0 y at the time of diagnosis. We compared bone metabolism and bone mass values in these patients with those in 428 healthy white children aged 11.3 +/- 0.2 y. Bone-specific alkaline phosphatase (a bone formation index) and N-terminal telopeptide of type I collagen (NTx; a bone resorption marker) were measured at the time of diagnosis and after 2, 6, and 12 mo of the GFD. Bone mineral content was measured at the lumbar spine and for the whole skeleton. RESULTS: The bone mineral content of patients was significantly lower than that of control subjects at the time of diagnosis but not after 1 y of the GFD. Serum bone-specific alkaline phosphatase concentrations of patients were significantly lower than those of control subjects at the time of diagnosis (P = 0.0064) and increased gradually and significantly during the GFD (ANOVA F = 4.71; P = 0.024). Conversely, patients with untreated disease had significantly higher urinary concentrations of NTx than did healthy control subjects (P < 0.0001). Urinary concentrations of NTx were not significantly affected by treatment (P = 0.37). CONCLUSIONS: The rate of bone metabolism is altered in children with untreated celiac disease, and these alterations may be the cause of osteopathy. Remarkable changes occur after the initiation of a GFD, and they result in a more balanced equilibrium.

Autosomal dominant hypocalcemia caused by a novel mutation in the loop 2 region of the human calcium receptor extracellular domain.

We report a novel missense mutation N124K in the extracellular calcium receptor (CaR) identified in two related subjects with the phenotypic features of autosomal dominant hypocalcemia (ADH). Expression of the N124K mutant receptor created by site-directed mutagenesis and transfected into HEK-293 cells was comparable with that of the wild-type (WT) receptor and two other mutant receptors N118K and L125P identified in subjects with ADH. Functional characterization by the extracellular Ca2+ ion ([Ca2+]0)-stimulated phosphoinositide (PI) hydrolysis in transfected HEK-293 cells showed that the N124K mutant receptor was left-shifted in Ca2+ sensitivity. This biochemical gain-of-function is comparable with that seen in other missense mutations of the CaR identified in subjects with ADH. We tested a series of missense substitutions (R, Q, E, and G) in addition to K for N124 and found that only the N124K mutation and to a much lesser extent N124R caused a left shift in Ca2+ sensitivity. Thus, a specific substitution, not merely a mutation of the N124 residue, is required for receptor activation. The N124K mutation is one of eight naturally occurring mutations in subjects with ADH identified in a short segment A116-C129 of the CaR extracellular domain (ECD). We present a hypothesis to explain receptor activation by mutations in this region based on the recently described three-dimensional structure of the related metabotropic glutamate type 1 receptor (mGluR1).

Germline mutations of TSH receptor gene as cause of nonautoimmune subclinical hypothyroidism.

Germline loss-of-function mutations of TSH receptor (TSHR) gene have been described in families with partial or complete TSH resistance. Large TSH elevations were generally found in the patients with homozygous or compound heterozygous mutations. In this study, we sequenced the entire TSHR gene in a series of 10 unrelated patients with slight (6.6-14.9 mU/liter) to moderate (24-46 mU/liter) elevations of serum TSH, associated with definitely normal free thyroid hormone concentrations. Thyroid volume was normal in all patients, except two with a modest hypoplasia. Autoimmune thyroid disease was excluded in all patients on the basis of clinical and biochemical parameters. Eight patients had at least one first-degree relative bearing the same biochemical picture. TSHR mutations were detected in 4 of 10 cases by analyzing DNA from peripheral leukocytes. A compound heterozygosity (P162A on maternal allele, and the novel mutation C600R on the paternal one) was found in the patient with the highest TSH levels. Only one TSHR allele was mutated in the remaining three cases, and no alterations in TSHR gene promoter were detected in all of these probands. A novel mutation (L467P) was detected on the maternal allele in one patient and in her monozygotic twin. Previously described inactive mutants, T655Delta and C41S, were detected in the other two cases. When tested on several occasions, circulating TSH values fluctuating above the upper limit of the normal range could be shown in heterozygous subjects of these families. A dominant mode of inheritance of the biochemical alterations was detected in these cases. Mutant TSHRs were studied during transient expression in COS7 and HEK293T cells. Their TSH-independent cAMP accumulation activities were very low or similar to mock-transfected cells, and no increases were seen after maximal hormone stimulation. Flow cytometry experiments showed a poor level of expression of all mutant TSHRs at the cell membrane. In conclusion, we found several loss-of-function mutations of TSHR, including two novel ones, in a series of unrelated patients with slightly elevated TSH levels. Therefore, partial resistance to TSH action is a frequent finding among patients with slight hyperthyrotropinemia of nonautoimmune origin. Germline mutations of TSHR may be associated with serum TSH values fluctuating above the upper limit of the normal range, also in the heterozygous state.

Polymorphism of vitamin D receptor gene start codon in patients with calcium kidney stones.

BACKGROUND: A linkage has been detected between vitamin D receptor (VDR) locus and calcium kidney stone disease. In order to assess the eventual role of VDR gene start codon polymorphisms in stone production, we analyzed the genotype-phenotype association in a group of patients with calcium kidney stones. METHODS: One hundred and fifty-five patients were studied. VDR genotypes were characterized at the translation start site by restriction fragment length polymorphism analysis, using endonuclease FokI. Phenotypes of calcium-phosphate metabolism were compared in patients with different genotypes: strontium enteral absorption (used as a surrogate marker for calcium absorption), bone mineral density (BMD), calcium and phosphate excretion were measured. RESULTS: Genotype distribution was not different in hypercalciuric and normocalciuric stone formers. Enteral strontium absorption, calcium excretion and BMD did not vary with the patient's genotype. Serum concentrations of phosphate (p=0.022) and renal threshold for phosphate excretion (p=0.026) were lower in patients with genotype FF (homozygous for the absence of the FokI site) than in those with genotype ff (homozygous for the presence of the FokI site). The lower phosphatemia was confirmed in FF hypercalciuric patients, but not in normocalciuric ones. Serum concentrations of phosphate and calcitriol in the group of hypercalciuric patients were inversely correlated with the genotype FF. CONCLUSIONS: The FokI genotype does not appear to be involved in the causes of idiopathic hypercalciuria and kidney stones. Hypercalciuric patients with FF genotype may be a subgroup with low plasma concentrations of phosphate, predisposed to tubular leakage of phosphate.