title: Effect of 3'UTR RET Variants on RET mRNA Secondary Structure and Disease Presentation in Medullary Thyroid Carcinoma.
abstract: BACKGROUND
  The RET S836S variant has been associated with early onset and increased risk for metastatic disease in medullary thyroid carcinoma (MTC). However, the mechanism by which this variant modulates MTC pathogenesis is still open to discuss. Of interest, strong linkage disequilibrium (LD) between RET S836S and 3'UTR variants has been reported in Hirschsprung's disease patients.
  
  
  OBJECTIVE
  To evaluate the frequency of the RET 3'UTR variants (rs76759170 and rs3026785) in MTC patients and to determine whether these variants are in LD with S836S polymorphism.
  
  
  METHODS
  Our sample comprised 152 patients with sporadic MTC. The RET S836S and 3'UTR (rs76759170 and rs3026785) variants were genotyped using Custom TaqMan Genotyping Assays. Haplotypes were inferred using the phase 2.1 program. RET mRNA structure was assessed by Vienna Package.
  
  
  RESULTS
  The mean age of MTC diagnosis was 48.5±15.5 years and 57.9% were women. The minor allele frequencies of RET polymorphisms were as follows: S836S, 5.6%; rs76759170, 5.6%; rs3026785, 6.2%. We observed a strong LD among S836S and 3'UTR variants (|D'| = -1, r2 = 1 and |D'| = -1, r2 = 0,967). Patients harboring the S836S/3'UTR variants presented a higher percentage of lymph node and distant metastasis (P = 0.013 and P<0.001, respectively). Accordingly, RNA folding analyses demonstrated different RNA secondary structure predictions for WT(TCCGT), S836S(TTCGT) or 3'UTR(GTCAC) haplotypes. The S836S/3'UTR haplotype presented a greater number of double helices sections and lower levels of minimal free energy when compared to the wild-type haplotype, suggesting that these variants provides the most thermodynamically stable mRNA structure, which may have functional consequences on the rate of mRNA degradation.
  
  
  CONCLUSIONS
  The RET S836S polymorphism is in LD with 3'UTR variants. In silico analysis indicate that the 3'UTR variants may affect the secondary structure of RET mRNA, suggesting that these variants might play a role in posttranscriptional control of the RET transcripts.
authors.affiliation: Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: Lucieli
authors.initials: L
authors.lastname: Ceolin
authors.affiliation: Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: Mirian
authors.initials: M
authors.lastname: Romitti
authors.affiliation: Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: Débora Rodrigues
authors.initials: DR
authors.lastname: Siqueira
authors.affiliation: Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: Carla
authors.initials: C
authors.lastname: Vaz Ferreira
authors.affiliation: Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: Jessica
authors.initials: J
authors.lastname: Oliboni Scapineli
authors.affiliation: Pathology Department, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Assis-Brazil
authors.affiliation: Department of Physics, Computational Biophysics Group, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Vieira Maximiano
authors.affiliation: Department of Physics, Computational Biophysics Group, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Tauanne
authors.initials: T
authors.lastname: Dias Amarante
authors.affiliation: Department of Physics, Computational Biophysics Group, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Miriam Celi
authors.initials: MC
authors.lastname: de Souza Nunes
authors.affiliation: Department of Physics, Computational Biophysics Group, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Gerald
authors.initials: G
authors.lastname: Weber
authors.affiliation: Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: Ana Luiza
authors.initials: AL
authors.lastname: Maia
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics*; D018278:Carcinoma, Neuroendocrine / Q000235:genetics* / Q000473:pathology*; D003198:Computer Simulation; D005260:Female; D005787:Gene Frequency / Q000235:genetics; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D006239:Haplotypes / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D015810:Linkage Disequilibrium / Q000235:genetics; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D009690:Nucleic Acid Conformation; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics*; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000473:pathology*
chemical_list: D020413:3' Untranslated Regions; D012333:RNA, Messenger; D051096:Proto-Oncogene Proteins c-ret
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