Título:	Deficiência parcial da proteína transportadora de tiroxina (TBG) : estudo do gene serpina7 e padrão de inativação do cromossomo x em uma família brasileira
Autor(es):	Maciel, Andrêssa Aby Faraj Linhares
Orientador(es):	Porto, Adriana Lofrano Alves
Assunto:	Hormônio - deficiência Tireóide - hormônio
Data de publicação:	6-Jan-2017
Data de defesa:	22-Ago-2016
Referência:	MACIEL, Andrêssa Aby Faraj Linhares. Deficiência parcial da proteína transportadora de tiroxina (TBG): estudo do gene serpina7 e padrão de inativação do cromossomo x em uma família brasileira. 2016. 118 f., il. Tese (Doutorado em Ciências da Saúde)— Universidade de Brasília, Brasília, 2016.
Abstract:	Background: Thyroxine-binding globulin (TBG) is the major human thyroid hormone transport protein. Inherited TBG abnormalities that implicated the protein’s structure and function result in complete (TBG-CD) and partial (TBG-PD) and TBG deficiency. The SERPINA7 gene encodes TBG and it is located on the long arm of the X chromosome (Xq22.2). Objectives: The purpose of this study was to perform the molecular analysis of the SERPINA7 gene in a Brazilian family with TBG-PD, investigate the X-chromosome inactivation pattern region comprising the gene as well as perform structural modeling of the mutant protein and comparative structural analysis of the serpin family of proteins, in order to infer functional effects of these mutations. Methods: Genomic DNA was extracted from the female proband, her father, her dizygotic twin sister and her two brothers. The samples were subjected to polymerase chain reaction (PCR) for SERPINA7 gene amplification and the products were sequenced by the Sanger method. The proband’s sample was evaluated by methylation analysis using the human androgen receptor (AR) gene, which is located next to the TBG gene (Xq11.2). Structural analysis of the serpin family was analyzed using PFSTATS and was also used to map equivalent positions in all human homologs. The molecular modeling was using the protocol described by Feyfant et al. Results: A novel missense mutation in the SERPINA7 gene (p.R35W) was found in heterozygosity in the proband and in hemizygosity in her brothers. They presented low serum TBG levels compatible with TBG-PD. This mutation consisted in a single nucleotide substitution (C>T) at position 163 of exon 1 which resulted in the replacement of an arginine by a tryptophan at codon 35. The proband expressed an Xchromosome inactivation ratio of 20:80. In this mutation, the alpha carbon of residue 35 is about 17Å away from the closest atom from T4 and this residue lies in a helix, with its side chain facing the solvent. Arg35 is also involved in electrostatic interactions with the main chain oxygens of Met264 and Asp261, and also the oxygen on the carboxamide group in Asn32, besides interacting with two waters molecules. The conservation and correlation patterns involving this residue, it can be seen that the most frequent residues in these positions are lysines (26.7%), arginines (18.4%) and glutamines (10.8%). Tryptophans are extremely rare (0.1%), and there is no significant (p<10-10) pairwise correlations involving residues in this position. Conclusion: This study reported a new variant of the SERPINA7 gene associated with TBG-PD in three siblings: one woman and two men. The X-chromosome inactivation pattern verified in the proband corroborated that deviations in the inactivation pattern account for genotype-phenotype variability in women with heterozygous mutations in the SERPINA7 gene, a rare condition. The hydrophobic nature of tryptophan would result in an apolar patch that would be significantly exposed to the solvent can result in protein aggregation and/or misfolding, and the consequent defect in the serum T4 transport. Additionally, these findings suggest that the TBG and its homologs in the serpin family could be similarly affected by mutations in this position which would disrupt the interaction network to its neighbors in the native structure, with probable functional impact.
Unidade Acadêmica:	Faculdade de Ciências da Saúde (FS)
Informações adicionais:	Tese (doutorado)—Universidade de Brasília, Faculdade de Ciências da Saúde, Programa de Pós-Graduação em Ciências da Saúde, 2016.
Programa de pós-graduação:	Programa de Pós-Graduação em Ciências da Saúde
Licença:	A concessão da licença deste item refere-se ao termo de autorização impresso assinado pelo autor com as seguintes condições: Na qualidade de titular dos direitos de autor da publicação, autorizo a Universidade de Brasília e o IBICT a disponibilizar por meio dos sites www.bce.unb.br, www.ibict.br, http://hercules.vtls.com/cgi-bin/ndltd/chameleon?lng=pt&skin=ndltd sem ressarcimento dos direitos autorais, de acordo com a Lei nº 9610/98, o texto integral da obra disponibilizada, conforme permissões assinaladas, para fins de leitura, impressão e/ou download, a título de divulgação da produção científica brasileira, a partir desta data.
DOI:	http://dx.doi.org/10.26512/2016.08.T.22087
Aparece nas coleções:	Teses, dissertações e produtos pós-doutorado

Os itens no repositório estão protegidos por copyright, com todos os direitos reservados, salvo quando é indicado o contrário.