Combined pituitary hormone deficiency caused by a novel mutation of a highly conserved residue (F88S) in the homeodomain of PROP-1

Mutations in the pituitary-specific paired-like homeodomain transcription f actor, PROP-1, result in combined pituitary hormone deficiency. We studied a Brazilian girl, offspring of first cousins, who presented with short stat ure and deficiencies of GH, TSH, PRL, LH, and FSH. Her cortisol response to hypoglycemia was determined at age 4.9, 10.7, and 14.1 yr and remained nor mal. Magnetic resonance imaging at the age of 9 yr revealed an anterior pit uitary lobe of diminished height (3 mm; normal, 4.5 +/- 0.6), but radiograp hy revealed a sella turcica volume above the normal mean. Direct sequencing of the PROP-I gene revealed homozygosity for a novel 263T >C transition that results in the replacement of a highly conserved phenyla lanine by serine at codon 88 (F88S). F88 constitutes the hydrophobic core o f the first helix of the homeodomain of PROP-1, and the substitution by the polar residue serine is expected to alter the secondary structure and impa ir binding of the mutated PROP-1 to DNA target sequences. The F88S mutation (which corresponds to murine F85S) was introduced into the murine Prop-1 c omplementary DNA and its consequences on DNA binding and traits-activation were assessed in vitro. In contrast to wild-type Prop-1, the F88S mutant sh owed no significant DNA binding to a PRDQ9 Prop-1 response element in gel s hift assays. Transcriptional activation of a luciferase reporter gene conta ining a PRDQ9 site upstream of a simian virus 40 promoter was reduced to ap proximately 34% compared with that of wild-type Prop-1 in transiently trans fected TSA-201 human embryonic kidney cells. The F88S mutation further expa nds the repertoire of mutations in PROP-1.