Combined Pituitary Hormone Deficiency Caused by a Novel Mutation of a Highly Conserved Residue (F88S) in the Homeodomain of PROP-1

Abstract

Mutations in the pituitary-specific paired-like homeodomain transcription factor, PROP-1, result in combined pituitary hormone deficiency. We studied a Brazilian girl, offspring of first cousins, who presented with short stature 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 normal. Magnetic resonance imaging at the age of 9 yr revealed an anterior pituitary lobe of diminished height (3 mm; normal, 4.5 +/- 0.6), but radiography revealed a sella turcica volume above the normal mean. Direct sequencing of the PROP-1 gene revealed homozygosity for a novel 263T>C transition that results in the replacement of a highly conserved phenylalanine by serine at codon 88 (F88S). F88 constitutes the hydrophobic core of 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 impair 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 complementary DNA and its consequences on DNA binding and trans-activation were assessed in vitro. In contrast to wild-type Prop-1, the F88S mutant showed no significant DNA binding to a PRDQ9 Prop-1 response element in gel shift assays. Transcriptional activation of a luciferase reporter gene containing a PRDQ9 site upstream of a simian virus 40 promoter was reduced to approximately 34% compared with that of wild-type Prop-1 in transiently transfected TSA-201 human embryonic kidney cells. The F88S mutation further expands the repertoire of mutations in PROP-1.

Unusual Phenotypic Features in a Patient with a Novel Splice Mutation in the GHRHR Gene

“…It was thought that patients with a GHRHR molecular defect invariably have anterior pituitary hypoplasia (15,(25)(26)(27)(28)(29), and that GHRHR mutations can be excluded in the absence of this feature because GHRHR is critical for pituitary development and function of somatotroph cells (30)(31). However, patients homozygous for a GHRHR splice site mutation (IVS1 + 1G > A), presumably with molecular consequences identical to those documented in our patients, and with normal anterior pituitary have been reported recently (29).…”

Hypothalamic and pituitary development: novel insights into the aetiology

“…The majority of these mutations are predicted to result in complete loss of function of the protein by ablating DNA binding and transcriptional activation. However, in vitro analysis has shown that some missense mutations retain partial activity (76,81,82). By far, the most common mutation (50-72% of all familial PROP1 mutations) (77,78,83), detected in multiple unrelated families from several different countries, is a 2 bp deletion among three tandem GA repeats ( 296 -GAGAGAG-302 ) within exon 2 resulting in a frameshift at codon 101 and the introduction of a termination codon at position 109 (often referred to as S109X), and probably represents a mutational hot spot within the gene, rather than a single common founder mutation (84).…”

Molecular analysis of the PROP1 and HESX1 genes in patients with septo-optic dysplasia and/or pituitary hormone deficiency

“…F88, which corresponds to position 20 of the homeodomain in transcription factors of this class, constitutes the hydrophobic core of the first α-helix forming the homeodomain. This finding underscores the critical role of this highly conserved hydrophobic phenylalanine in the structure and function of the homeodomain of PROP-1 (19).…”

“…Brickman and cols. (19), analyzing 461 patients, found 5 patients of Afro-Caribbean descent with variable severity of SOD with this allelic variant (9). Analyzing the DNA of 42 normal individuals of Afro-Caribbean background, they encountered 5 individuals homozygous for the wild-type allele, 17 individuals homozygous and 20 heterozygous for the 59 A > G; N125S allelic variant.…”