In Vitro Impairment of STAT5b Activation by Gain-of-Function STAT3 Mutations

RAMIREZ URREA LAURA; JASPER HÉCTOR; DOMENÉ HORACIO; SCAGLIA PAULA; HWA VIVIAN; GUTIÉRREZ MARIANA; KARABATAS LILIANA; ASHISH KUMAR

Chicago

Congreso; Endo Meeting 2018; 2018

Endocrine Society

In Vitro Impairment of STAT5b Activation by Gain-of-Function STAT3 MutationsBackground: Germinal heterozygous activating STAT3 mutations represent a novel monogenic defect associated with multi-organ autoimmune disease and severe growth retardation. We recently characterized two novel gain-of-function (GOF) STAT3 variants (p.E616del and p.C426R) identified by whole-exome sequencing in two unrelated pediatric patients with IGF-I deficiency and immune dysregulation. Aim: Our objective was to in vitro characterize the effect of GH treatment on STAT3 GOF variants activity and, additionally, to determine how these mutants affect the GH-signalling pathway by studying STAT5b function. Methods: STAT3 gene variants were generated by site-directed mutagenesis and transfected into HEK293T cells overexpressing the GHR. The impact of these mutations on STAT3 and STAT5b expression, phosphorylation, location, and activity was studied using Western Immunoblot, immunohistochemistry, and luciferase reporter assays. Results: Functional analyses showed that both variants increased STAT3-mediated transcriptional activities in response to GH (p