Post-receptor IGF1 insensitivity restricted to the MAPK pathway in a Silver-Russell syndrome patient with hypomethylation at the imprinting control region on chromosome 11

Autor(es)

Montenegro, Luciana R. ^[1] ; Leal, Andrea C. ^[1] ; Coutinho, Debora C. ^[1] ; Valassi, Helena P. L. ^[1] ; Nishi, Mirian Y. ^[1] ; PArnhold, Ivo J. ^[1] ; Mendonca, Berenice B. ^[1] ; Jorge, Alexander A. L. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Lab Hormonios & Genet Mol LIM 42, Unidade Endocrinol Desenvolvimento, Disciplina Endocrinol, Hosp Clin, Fac Med, BR-01246903 Sao Paulo - Brazil

^[2] Univ Sao Paulo, Lab Endocrinol Celular & Mol LIM 25, Unidade Endocrinologia Genet, Disciplina Endocrinol, Hosp Clin, Fac Med, Fac Med U, BR-01246903 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: EUROPEAN JOURNAL OF ENDOCRINOLOGY; v. 166, n. 3, p. 543-550, MAR 2012.
• Citações Web of Science: 7

Resumo

Background: Hypomethylation of the paternal imprinting center region 1 (ICR1) is the most frequent molecular cause of Silver-Russell syndrome (SRS). Clinical evidence suggests that patients with this epimutation have mild IGF1 insensitivity. Objective: To assess in vitro IGF1 action in fibroblast culture from a patient with SRS and IGF1 insensitivity. Methods: Fibroblast cultures from one patient with SRS due to ICR1 demethylation and controls were established. The SRS patient has severe growth failure, elevated IGF1 level, and poor growth rate during human recombinant GH treatment. IGF1 action was assessed by cell proliferation, AKT, and p42/44-MAPK phosphorylation. Gene expression was determined by real-time PCR. Results: Despite normal IGF1R sequence and expression, fibroblast proliferation induced by IGF1 was 50% lower in SRS fibroblasts in comparison with controls. IGF1 and insulin promoted a p42/44-MAPK activation in SRS fibroblasts 40 and 36%, respectively, lower than that in control fibroblasts. On the other hand, p42/44-MAPK activation induced by EGF stimulation was only slightly reduced (75% in SRS fibroblasts in comparison with control), suggesting a general impairment in MAPK pathway with a greater impairment of the stimulation induced by insulin and IGF1 than by EGF. A PCR array analysis disclosed a defect in MAPK pathway characterized by an increase in DUSP4 and MEF2C gene expressions in patient fibroblasts. Conclusion: A post-receptor IGF1 insensitivity was characterized in one patient with SRS and ICR1 hypomethylation. Although based on one unique severely affected patient, these results raise an intriguing mechanism to explain the postnatal growth impairment observed in SRS patients that needs confirmation in larger cohorts. (AU)

• Processo FAPESP: 05/50144-2 - Determinação da sensibilidade ao IGF-1 de fibroblastos de crianças nascidas pequenas para a idade gestacional
• Beneficiário: Luciana Ribeiro Montenegro
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 08/57915-2 - Caracterização da insensibilidade ao fator de crescimento insulina-símile tipo 1 (IGF-1) em pacientes com defeitos no receptor ou na via de sinalização do receptor tipo 1 de IGFs (IGF-1R)
• Beneficiário: Andréa de Castro Leal
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 05/04726-0 - Caracterização molecular das doenças endócrinas congênitas que afetam o crescimento e o desenvolvimento
• Beneficiário: Ana Claudia Latronico Xavier
• Modalidade de apoio: Auxílio à Pesquisa - Temático