Molecular and Gene Network Analysis of Thyroid Transcription Factor 1 (TTF1) and Enhanced at Puberty 1 (EAP1) Genes in Patients with GnRH-Dependent Pubertal Disorders

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 596-621-Pediatric Endocrinology /Steroids and Puberty
Clinical
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-613
Priscilla Cukier*1, Hollis Wright2, TOmke Rulfs3, Leticia Gontijo Silveira4, Milena Gurgel Teles5, Berenice Bilharinho Mendonca1, Ivo J Arnhold1, Sabine Heger6, Sergio R Ojeda7, Ana Claudia Latronico8 and Vinicius N. Brito1
1Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil, 2Oregon National Primate Research Center/Oregon Health and Science University (ONPRC/OHSU), Oregon, USA, 3Institute of Clinical Biochemistry, Hannover Medical School, Hannover, Germany, 4Hosp das Clinicas/USP, Sao Paulo, Brazil, 5Hosp da Clinicas Sao Paulo, Sao Paulo, Brazil, 6Univ Hosp Leipzig, Leipzig, Germany, 7Oregon National Primate Res Ctr, Beaverton, OR, 8University of Sao Paulo, Sao Paulo-SP, Brazil
Background: Thyroid transcription factor-1 (TTF1) and enhanced at puberty (EAP1) are transcription factors that enhance GnRH expression. Abnormalities in genes encoding these proteins may be implicated in GnRH-dependent pubertal disorders

Aim: To investigate the potential contribution of sequence variation in the TTF1 and EAP1 genes to central pubertal disorders in a large cohort of patients.

Patients and Methods: We selected 133 patients with diagnosis of GnRH-dependent pubertal disorders: idiopathic central precocious puberty (idiopathic CPP; n=71), central precocious puberty due to hypothalamic hamartoma (CPPH; n=15) and normosmic isolated hypogonadotropic hypogonadism (nIHH; n=47).  PCR and sequencing of the encoding regions of EAP1 and TTF1, as well as the putative promoter region of TTF1 were performed on DNA from peripheral blood leukocytes to identify sequence variations in these genes.  Size variation of polyglutamine (polyQ) and polyalanine (polyAla) repeats in EAP1 were analyzed by fragment size analysis using GeneScan software.  The association of TTF1 and EAP1 to genes implicated in regulating the timing of human puberty was investigated using the meta-network framework GeneMANIA and the resulting networks were visualized using Cytoscape software.

Results: Direct sequencing of the entire mRNA of TTF1, its boundaries and its putative promoter region did not reveal any mutation or polymorphisms. Regarding EAP1, 4 synonymous variants (p.E87E, p.A163A, p.Y415Y and p.C758C) were identified with similar frequencies among idiopathic CPP, CPPH, nIHH, and control individuals (p>0.05). The EAP1 polyQ region ranged from 22 to 29 glutamine repeats, but genotype frequencies were not different among the groups (p>0.05). The length of the EAP1 5’distal polyAla region ranged from 9 to 16 alanine repeats in all subjects. The most common genotype was the homozygous 12/12 (95.3% CPP patients, 100% nIHH, 96% controls), but the heterozygous genotype 12/9 was only identified in two sisters with idiopathic CPP. Functional analysis did not reveal any alteration in EAP1 transcriptional activity associated to this sequence variation. There were no significant allele and genotype differences in the length of alanine tract among the groups (p > 0.05).  Despite this lack of sequence variation, both TTF1 and EAP1 were found to be integral components of genetic networks formed by genes implicated in the control of menarche

Conclusion:  Using a limited number of cases, no TTF1 or EAP1 germline mutations were found to be associated with GnRH-dependent pubertal disorders in humans. Although we cannot exclude somatic mutations, our results are compatible with the view that changes in TTF1 and EAP1 expression affecting human puberty may occur as a consequence of functional alterations in gene networks associated with the timing of puberty.

Nothing to Disclose: PC, HW, TR, LGS, MGT, BBM, IJA, SH, SRO, ACL, VNB

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: FAPESP (06/56531-0 to PC) and CNPq (300828/2005-5 to BBM and 300469/2005 to ACL), the US National Science Foundation (NSF IOS1121691 to SRO), NIH grant 8P51-OD-011092-53 for the operation of the Oregon National Primate Research Center (SRO), and the German Research Foundation Grant HE 3151/4-1 (SH). H.W was a postdoctoral fellow supported by NIH Training Grant T32 HD007133