A novel GATA3 frameshift mutation causes hypoparathyroidism, sensorineural deafness, and renal dysplasia syndrome.

BACKGROUND: Hypoparathyroidism, sensorineural deafness, and renal dysplasia (HDR) syndrome (Barakat syndrome) is a rare autosomal dominant disorder caused by mutations in the gene encoding GATA3 on chromosome 10p14.

METHOD: Informed consent was obtained from a 38-year-old female patient. 5 mL of venous blood was collected and sent for whole-exome sequencing. GATA3 constructs of both wild-type and mutant were transfected into HEK-293 T cells. Three-dimensional modeling, luciferase-reporter gene test, western blotting and cellular immunofluorescence were used to evaluate the effect of the mutation.

RESULTS: A novel frameshift mutation c. 677dup(p.Pro227AlafsTer77), named P227Afs, was found in GATA3 . Three-dimensional modeling revealed that the mutation caused the loss of the dual zinc finger structures 1 and 2 (ZNF1 and ZNF2) of the synthesized protein. Expression of wild-type GATA3 produced a six-fold increase in luciferase activity when compared with pcDNA3.1 vector only ( P  < 0.001), whereas the P227Afs mutant showed no increase. The mutation significantly reduced the transcriptional activity of GATA3 . Immunofluorescence and western blotting analyses demonstrated that the mutation changed the nuclear location of GATA3 and caused difficulty in nuclearization.

CONCLUSION: A novel heterozygous frameshift mutation in GATA3 was identified and showed to result in difficult nuclearization, and a dominant-negative effect on the wild-type.