Characterization of GATA3 mutations in the hypoparathyroidism, deafness, and renal dysplasia (HDR) syndrome

The hypoparathyroidism, deafness, and renal dysplasia (HDR) syndrome is an autosomal dominant disorder caused by mutations of the dual zinc finger transcription factor, GATA3. The C-terminal zinc finger (ZnF2) binds DNA, whereas the N-terminal finger (ZnF1) stabilizes this DNA binding and interacts with other zinc finger proteins, such as the Friends of GATA ( FOG). We have investigated seven HDR probands and their families for GATA3 abnormalities and have identified two nonsense mutations (Glu-228 --> Stop and Arg- 367 --> Stop); two intragenic deletions that result in frameshifts from codons 201 and 355 with premature terminations at codons 205 and 370, respectively; one acceptor splice site mutation that leads to a frameshift from codon 351 and a premature termination at codon 367; and two missense mutations (Cys-318 --> Arg and Asn-320 --> Lys). The functional effects of these mutations, together with a previously reported GATA3 ZnF1 mutation and seven other engineered ZnF1 mutations, were assessed by electrophoretic mobility shift, dissociation, yeast two-hybrid and glutathione S-transferase pull-down assays. Mutations involving GATA3 ZnF2 or adjacent basic amino acids resulted in a loss of DNA binding, but those of ZnF1 either lead to a loss of interaction with specific FOG2 ZnFs or altered DNA-binding affinity. These findings are consistent with the proposed three-dimensional model of ZnF1, which has separate DNA and protein binding surfaces. Thus, our results, which expand the spectrum of HDR-associated GATA3 mutations and report the first acceptor splice site mutation, help to elucidate the molecular mechanisms that alter the function of this zinc finger transcription factor and its role in causing this developmental anomaly.