Tu156 - A GATA3 Frameshift Mutation Alters DNA-binding Causing Loss of Th2 Polarization in a Patient with Hypoparathyroidism, Sensorineural Deafness, and Renal Dysplasia Syndrome

GATA3 is a highly conserved transcription factor important in development and in the immune system.  It is the master transcription factor driving T helper type 2 (Th2) polarization. GATA3 acts as a homodimer with each monomer containing transactivation domains, zinc finger domains, and an uncharacterized C-terminus. Heterozygous loss-of-function mutations in GATA3 cause hypoparathyroidism, sensorineural deafness and renal dysplasia (HDR) syndrome. GATA3 mutations causing loss of one functional allele decrease Th2 function.  However, the impact of GATA3 frameshift mutations on Th2 function has not been assessed.  We identified a heterozygous frameshift elongation mutation, GATA3^M401Vfs*106, in a patient with HDR syndrome and juvenile idiopathic arthritis. GATA3^M401Vfs*106 has intact DNA binding domains and disrupts the poorly understood C-terminus. An in vitro Th2 polarization assay was performed on patient cells. The Th2 polarized cells were examined for GATA3 expression, gene transcription, cytokine production, and GATA3 DNA-binding. GATA3^M401Vfs*106 Th2 cells expressed GATA3 and GATA3^M401Vfs*106 by Western blot. GATA3^M401Vfs*106 Th2 polarized cells had decreased Th2 function identified by lower production of the cytokines IL-5 and IL-13. Chromatin immunoprecipitation sequencing analysis of genome wide GATA3 DNA-binding in GATA3^M401VfsX106 Th2 polarized cells identified unique and overlapping binding peaks throughout the genome with enrichment of non-GATA3 associated motifs. This study identified that frameshift mutations in the C-terminus of GATA3 decrease Th2 function by altering GATA3 DNA binding, gene expression, and production of cytokines. This study reveals that the GATA3 C-terminus has an important role in Th2 polarization.