Molecular defect in activation of a mutant Stat5b

A recent report identified a patient presenting with clinical features of growth hormone insensitivity, who harbored a homozygous mis-sense mutation in the Stat5b gene that resulted in an alanine to proline substitution at amino acid 630, adjacent to the SH2 domain. The precise molecular defect caused by the mutant Stat5b protein has not been elucidated. Preliminary experiments have demonstrated that the mutant Stat5b protein is detected upon transient transfection in cultured mammalian cells, however at consistently