Análise dos genes GHRH e GL12 em pacientes com deficiência de hormônio do crescimento congênita / GHRH and GLI2 genes analysis in patients with congenital growth hormone deficiency

AUTOR(ES)

Marcela Moura França

FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

14/02/2012

RESUMO

Introduction: Alterations in genes related to GH secretion and pituitary organogenesis have been identified in patients with congenital GH deficiency (GHD). However, in only few cases of GHD the etiology has been established. GH-releasing hormone (GHRH) is an obvious candidate to explain isolated GH deficiency (IGHD). Previous reports in the literature did not identify mutations in GHRH, however, the methodology used was limited. Most patients with combined pituitary hormone deficiency (CPHD) have an ectopic posterior pituitary lobe (EPP) suggesting the study of genes involved in early pituitary development and also expressed in the infundibulum. GLI2 is a transcription factor in Sonic hedgehog signaling expressed in the primordial Rathkes pouch and ventral diencephalon during early pituitary development. Previously, GLI2 mutations were found in patients with holoprosencephaly and pituitary abnormalities. Aim: Analyse GHRH in 151 patients with IGHD (42 Brazilian and 101 from international centers) and GLI2 in 180 Brazilian patients with IGHD or CPHD by PCR and automatic sequencing, and describe the phenotype of patients with mutations. Results: In GHRH, six heterozygous variants that are benign according to in silico analysis were identified. GLI2 study revealed three novel heterozygous mutations leading to premature stop codons (p.L788fsX794, p.L694fsX722 e p.E380X) and truncated proteins, without the transcriptional activator domain. p.L788fsX794 was identified in a girl with short stature, polydactyly, epilepsy and hypoglycemia. She had GH, TSH, ACTH, prolactina, LH and FSH deficiencies. Two uncles had IGHD and one cousin CPHD. These relatives, the mother and other maternal relatives had polydactyly and carried the mutation. p.L694fsX722 was identified in a boy with short stature due to GHD who also had cleft lip and palate. His healthy father also carried the mutation. p.E380X was identified in an infant with delayed development, hypoglycemia, polyuria and polydipsia. She had GH, ACTH, TSH and ADH deficiencies. Her apparently normal mother also carried the mutation. All patients with GHD and GLI2 mutations had an EPP (not visualized in the patient with p.E380X), hypoplastic anterior pituitary lobe and absence of holoprosencephaly on MRI. Eighteen non-synonymous variants in GLI2 were identified in 24 patients. Sixteen of these were considered deleterious in at least one in silico prediction program and ten of these were not found in the control population. The phenotype was mainly of CPHD and EPP without holoprosencephaly. Several synonymous and intronic GLI2 variants and polymorphisms apparently without functional consequences were identified. Conclusions: No mutations in GHRH were identified and if mutations in this gene exist as a cause of IGHD, they must be very rare. Variants in GLI2 are frequent (15%) indicating its important role in the etiology of GHD. Furthermore, we expanded the clinical spectrum of patients with GLI2 mutations characterized by IGHD or CPHD including diabetes insipidus, ectopic posterior pituitary lobe (in most patients) and absence of holoprosencephaly. Additional features were polydactyly and midline facial defects and the inheritance was autosomal dominant with incomplete penetrance

ASSUNTO(S)

dedos de zinco fatores de transcrição gli2 protein gli2 proteína growth hormone-releasing hormone/genetics growth hormone/deficiency growth hormone/genetics hipófise/embriologia hipopituitarismo/etiologia hormônio do crescimento/deficiência hormônio do crescimento/genética hormônio liberador de hormônio do crescimento/genética hypopituitarism/etiology neuroipófise/anormalidades pituitary gland posterior/abnormalities pituitary/embryology transcription factors zinc fingers

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