Endocrine Abstracts

The hypoparathyroidism-deafness-renal dysplasia (HDR) syndrome is an autosomal dominant disorder caused by germline mutations of the dual zinc-finger (ZnF) transcription factor, GATA3. To date, 51 GATA3 mutations have been reported, which can be divided broadly into three structural-functional classes: i) mutations that lead to a loss of DNA binding and involve ZnF2; ii) mutations, usually of ZnF1, that bind DNA but result in reduced DNA binding affinity; and iii) mutations, mostly of ZnF1, that do not alter DNA binding or affinity but lose protein interaction. To gain further insights into the structural-functional consequences of GATA3 mutations, we investigated 31 HDR patients for GATA3 mutations. Venous blood was obtained after informed consent, as approved by the local ethical committee, and leukocyte DNA extracted. GATA3 specific primers were used for PCR amplification and the DNA sequence determined. Twenty-two germline heterozygous GATA3 mutations were identified, consisting of: nine missense mutations, four nonsense mutations, four frameshifting deletions, two frameshifting insertions and three splice site mutations. To further elucidate the molecular mechanisms altered by the mutants we functionally characterised six novel missense mutations: Arg299Gln, located in the linker region between ZnF1 and ZnF2; Thr326Ile, Arg330Trp, Ala341Asp, and Cys342Tyr, within ZnF2; and Tyr345Cys, located C-terminal to ZnF2. Investigation of nuclear localisation, DNA binding and gene transactivation revealed that: Thr326Ile resulted in loss of nuclear localisation; all the other mutations resulted in complete loss of DNA binding and reduction of transactivational activity by >90%, with the exception of Arg299Gln which led to decreased DNA binding and a >30% reduction of transactivational activity. Thus, our studies have identified an additional 22 germline GATA3 mutations, associated with HDR, including one that defines a fourth class of GATA3 mutation, which is located in the ZnF1-ZnF2 linker region, and has an intermediate effect on DNA binding and gene transactivation.

Declaration of funding: This work was supported by the Medical Research Council (MRC), UK (grant number G1000467/2010).