Mariela Caputo

Congenital hypothyroidism with goitre caused by new mutations in the thyroglobulin gene

Context  Thyroid dyshormonogenesis is associated with mutations in the thyroglobulin (TG) gene and characterized by normal organification of iodide and low serum TG. These mutations give rise to congenital goitrous hypothyroidism, transmitted in an autosomal recessive mode.

Recurrence of the p.R277X/p.R1511X compound heterozygous mutation in the thyroglobulin gene in unrelated families with congenital goiter and hypothyroidism: haplotype analysis using intragenic thyroglobulin polymorphisms

Thyroglobulin (TG) functions as the matrix for thyroid hormone synthesis. Thirty-five different loss-of-function mutations in the TG gene have been reported. These mutations are transmitted in an autosomal recessive mode. The objective of this study is to analyze the recurrence of the p.R277X/p.R1511X compound heterozygous mutation in the TG gene in two unrelated families (one Argentinian and another Brazilian) with congenital hypothyroidism, goiter and impairment of TG synthesis. The first and last exon of the TG gene, the exons where previously mutations and single nucleotide polymorphisms (SNPs) were detected, as well as the TG promoter, were analyzed by automatic sequencing in one affected member of the each family. Four microsatellite markers localized in introns 10, 27, 29 and 30 of the TG gene, one insertion/deletion intragenic polymorphism and 15 exonic SNPs were used for haplotype analysis. A p.R277X/p.R1511 compound heterozygous mutation in the TG gene was found in two members of an Argentinian family. The same mutations had been also reported previously in two members of a Brazilian family. We constructed mutation-associated haplotypes by genotyping members of the two families. Our results suggest that the cosegregating haplotype is different in each one of these families. Different haplotypes segregated with the p.R277X and p.R1511 mutations demonstrating the absence of a founder effect for these mutations between Argentinian and Brazilian populations. However, haplotyping of Argentinian patients showed the possibility that the p.R277X alleles might be derived from a common ancestral chromosome.

A DNA extraction method of small quantities of bone for high-quality genotyping.

DNA genotyping techniques have been used successfully in forensic science for almost three decades and represent the gold standard for individual identification. However, efficient protocols for obtaining DNA from exhumed bones suitable for genotyping are still scarce and most of them require a considerable amount of starting material, are time consuming and are inefficient for reducing inhibitors effects. We sought to develop an optimised protocol for extracting DNA from bone samples obtained from exhumations. We tested two approaches for preparing bone samples: (a) fine powder and (b) thin slices of bone. The best ratio of bone amount to DNA yields was assessed by a titration experiment using bone powder ranging from 50 to 1000mg. We obtained optimal DNA yields (27pg mg(-1) on average) when 150-200mg of starting material were processed using a one-step demineralisation method. Better-quality profiles (determined by the number of genotyped loci) were obtained when DNA was extracted from bone slices compared to extraction from bone powder. From bone slices 83.9% and from bone powder 46.7% of the samples provided genotypes for 11 or more loci. Since bone preparation procedures were carried out at room temperature, the method developed in the present study might be an attractive alternative to the standard freeze-mill approach, being faster and more cost-efficient.

Molecular analysis of congenital goitres with hypothyroidism caused by defective thyroglobulin synthesis. Identification of a novel c.7006C>T [p.R2317X] mutation and expression of minigenes containing nonsense mutations in exon 7.

Background  Thyroglobulin (TG) deficiency is an autosomal‐recessive disorder that results in thyroid dyshormonogenesis. A number of distinct mutations have been identified as causing human hypothyroid goitre.

Variable Number of Tandem Repeats of the Insulin Gene Determines Susceptibility to Latent Autoimmune Diabetes in Adults

AbstractBackground: The different clinical presentations of latent autoimmune diabetes in adults (LADA) and type 1 diabetes mellitus may be the result of susceptibility genes in determining the mode of onset. We analyzed the 5′ polymorphisms of the insulin mini-satellite region (INS), a variable number of tandem repeats (VNTR) [repeat units; RU]. We evaluated the association of the different INS-VNTR alleles in patient susceptibility to LADA autoimmune diabetes. To our knowledge, this constitutes the first study of this kind performed in a Caucasian population. Methods: From an group of 160 Argentinean patients previously characterized as having LADA, we selected 44 patients who presented with humoral autoimmunity for genotyping and compared them to 88 patients with type 1 diabetes and 138 healthy individuals. The INS-VNTR allele classes were determined by Southern blotting (class I: 21–44RU; class III: 138–159RU). Subjects with class I alleles were further studied using PCR amplification to determine the exact length of the alleles (short 1S: 22–37RU; medium 1M: 38–41RU; large 1L: 42–43RU). Allelic and genotype frequencies were estimated by χ2 tests for independence with 2 × 2 contingency tables and the relative risks (RR) were determined using GraphPad InStat software. Results: We observed differential associations among the class I alleles when comparing patients with LADA (80.6%) and type 1 diabetes (81.3%) with the controls (70%; p < 0.005). This increase was largely due to the high frequency of the 1S/S genotype (63.6% LADA vs 37% controls, with a p-value of 0.0019 [p1]; 53.4% type 1 diabetes vs 37% controls, with a p-value of 0.0149 [p2]). Remarkably, all LADA patients genotyped as class I homozygous had the shorter (S) class I allele (100%). Differences in the overall 1S distribution were observed: in LADA the 94.4% of the alleles were equal to or smaller than 35RU, while in patients with type 1 diabetes it was 78.3% and in controls 74.1%. Moreover, the relative risks associated with the 1S/S genotype for patients with LADA showed a substantial increase with respect to those with type 1 diabetes (52%) when we compare them to the controls (1S/S LADA/control, 2.282 [RR1] vs type 1 diabetes/control, 1.497 [RR2]). Conclusion: The presence of the 1S allele could be considered a risk factor in LADA patients, as previously reported for type 1 diabetes. The class I INS-VNTR allele in LADA increases genetic susceptibility to disease development.

Distribution of genetic polymorphisms associated with hepatitis C virus (HCV) antiviral response in a multiethnic and admixed population.

The prevalence of genetic polymorphisms identified as predictors of therapeutic-induced hepatitis C virus (HCV) clearance differs among ethnic groups. However, there is a paucity of information about their prevalence in South American populations, whose genetic background is highly admixed. Hence, single-nucleotide polymorphisms rs12979860, rs1127354 and rs7270101 were characterized in 1350 healthy individuals, and ethnicity was assessed in 259 randomly selected samples. The frequency of rs12979860CC, associated to HCV treatment response, and rs1127354nonCC, related to protection against hemolytic anemia, were significantly higher among individuals with maternal and paternal Non-native American haplogroups (64.5% and 24.2%), intermediate among admixed samples (44.1% and 20.4%) and the lowest for individuals with Native American ancestry (30.4% and 6.5%). This is the first systematic study focused on analyzing HCV predictors of antiviral response and ethnicity in South American populations. The characterization of these variants is critical to evaluate the risk–benefit of antiviral treatment according to the patient ancestry in admixed populations.

Identification and characterization of new variants of three associated SNPs and a microsatellite in the TSH receptor gene which are useful for genetic studies.

The purpose of the present work was to characterize g.IVS5-69C>T, g.IVS6+13C>T and c.561C>T SNPs and the [CT](n) microsatellite in the TSHR gene for genetic analysis. Exons 6 and 7 of the TSHR gene, including the flanking intronic sequences, were screened for the presence of g.IVS5-69C>T, g.IVS6+13C>T and c.561C>T SNPs by SSCP. We found genetic association between the three SNPs and a total of three different haplotypes were observed. Two were homozygous blocks, g.IVS5-69T/g.IVS6+13G/c.561C (Haplotype TGC, 3.3%) and g.IVS5-69C/g.IVS6+13A/c.561T (Haplotype CAT, 75%). Every individual who was heterozygous for g.IVS5-69C>T was equally heterozygous for g.IVS6+13A>G and c.561T>C (Haplotype CAT/TGC, 21.7%). The [CT](n) microsatellite, localized in intron 7 of the TSHR gene was amplified by PCR and the labeled products were separated in a polyacrylamide denaturing sequencing gel. Three variable numbers of CT motif were identified, two previously reported ([CT](6) and [CT](8)) and one previously unreported ([CT](9)). The construction and expression of the hybrid minigenes using pSPL3 and alpha-globin-fibronectin EDB (pTB) vectors showed that the [CT](n) microsatellite itself does not interfere with exon 8 definition and processing in vitro. In conclusion, g.IVS5-69C>T/g.IVS6+13C>T/c.561C>T haplotypes and [CT](n) microsatellite are informative polymorphic markers and can be used in linkage studies in families with germ line TSHR mutations or autoimmunity thyroid diseases.

Role of HLA-DP and HLA-DQ on the clearance of hepatitis B virus and the risk of chronic infection in a multiethnic population

HBV infection exhibits geographical variation in its distribution in South America. While HBV rates are low in central Argentina, the north‐western region exhibits intermediate HBV rates. Unfortunately, the reasons that could explain this difference are still unknown.

Species identification in forensic samples using the SPInDel approach: A GHEP-ISFG inter-laboratory collaborative exercise

DNA is a powerful tool available for forensic investigations requiring identification of species. However, it is necessary to develop and validate methods able to produce results in degraded and or low quality DNA samples with the high standards obligatory in forensic research. Here, we describe a voluntary collaborative exercise to test the recently developed Species Identification by Insertions/Deletions (SPInDel) method. The SPInDel kit allows the identification of species by the generation of numeric profiles combining the lengths of six mitochondrial ribosomal RNA (rRNA) gene regions amplified in a single reaction followed by capillary electrophoresis. The exercise was organized during 2014 by a Working Commission of the Spanish and Portuguese-Speaking Working Group of the International Society for Forensic Genetics (GHEP-ISFG), created in 2013. The 24 participating laboratories from 10 countries were asked to identify the species in 11 DNA samples from previous GHEP-ISFG proficiency tests using a SPInDel primer mix and control samples of the 10 target species. A computer software was also provided to the participants to assist the analyses of the results. All samples were correctly identified by 22 of the 24 laboratories, including samples with low amounts of DNA (hair shafts) and mixtures of saliva and blood. Correct species identifications were obtained in 238 of the 241 (98.8%) reported SPInDel profiles. Two laboratories were responsible for the three cases of misclassifications. The SPInDel was efficient in the identification of species in mixtures considering that only a single laboratory failed to detect a mixture in one sample. This result suggests that SPInDel is a valid method for mixture analyses without the need for DNA sequencing, with the advantage of identifying more than one species in a single reaction. The low frequency of wrong (5.0%) and missing (2.1%) alleles did not interfere with the correct species identification, which demonstrated the advantage of using a method based on the analysis of multiple loci. Overall, the SPInDel method was easily implemented by laboratories using different genotyping platforms, the interpretation of results was straightforward and the SPInDel software was used without any problems. The results of this collaborative exercise indicate that the SPInDel method can be applied successfully in forensic casework investigations.

Development of a quantitation approach for total human and male DNA based on Real Time PCR followed by High Resolution Melting analysis

We developed and validated a total human DNA quantitation technique that simultaneously allows male DNA detection. This assay, called Amel‐Y, is a duplex Real Time PCR followed by HRM (high resolution melting) analysis using the intercalating dye SYTO9. Amel‐Y duplex produces two amplicons, one for the amelogenin gene (106/112 bp, female/male) and another (84 bp) corresponding to human Y chromosome‐specific fragment to detect male DNA. After HRM analysis, two melting peaks differing in 5.3°C–5.5°C are detected if both male and female DNA are present and only one if only female DNA is present. For specificity assessment, the inclusion of high concentrations of bacterial and fungal DNA in the quantitation reactions allowed discarding species cross‐reactivity. A set of crime scene evidence from forensic casework has been quantified with commercial kits and compared with Amel‐Y duplex. Our method detected male DNA from a concentration of 18 pg/μL and supports autosomal/Y DNA detection ratio up to 200:1. A limitation of the technique is its inability to quantify male and female donnors in a mixed sample. The Amel‐Y duplex demonstrated to be an efficient system for quantifying total human DNA being a specific, rapid, sensitive, and cost‐effective method suitable for mixed DNA samples and applicable to any field where human DNA quantification is required, such as molecular diagnosis, population genetics, and forensic identification.