Identification and functional analysis of the novel S179R POU1F1 mutation associated with combined pituitary hormone deficiency.

CONTEXT: The pituitary-specific transcription factor 1 plays a key role in the development and differentiation of three pituitary cell types: somatotrophs, lactotrophs, and thyrotrophs. Several mutations of the human gene (called POU1F1) have been shown to be responsible for a phenotype of combined pituitary hormone deficiency involving GH, prolactin (PRL), and TSH. OBJECTIVE: We have identified a novel homozygous C to G mutation in exon 4 of the POU1F1 gene (S179R) in a patient with this rare phenotype. We analyzed the functional consequences of this S179R mutation associated with a single-amino acid change in the POU-specific domain. METHODS: Consequences of this mutation on transcriptional activities by transfection studies in alphaT3 cells, DNA binding ability by EMSA, structural properties, and nuclear accumulation of POU1F1 were investigated. RESULTS: The transactivation capacity of this mutant was markedly decreased on the GH1, PRL, TSHbeta, and POU1F1 genes. Interestingly, this mutation abolished the functional interaction of POU1F1 on the PRL promoter with the coactivator cAMP response element-binding protein-binding protein but not with the transcription factor LIM homeodomain transcription factor 3. The S179R mutant displayed normal nuclear accumulation but a markedly decreased binding to a DNA response element in keeping with crystallographic data, suggesting that the S179R mutation might interfere with DNA binding. CONCLUSIONS: Together with previous data, our study indicates that both DNA binding and interaction with cofactors like cAMP response element-binding protein-binding protein are critical for POU1F1 function and that functional and structural properties of abnormal POU1F1 proteins are variously influenced by the type of mutations.

Genetic screening of combined pituitary hormone deficiency: experience in 195 patients.

CONTEXT: Mutations in transcription factors result in combined pituitary hormone deficiency (CPHD). OBJECTIVE: A genetic screening strategy, based on endocrine and neuroradiological phenotype according to published knowledge, was applied to establish the prevalence of gene defects in each category of patients and provide a useful framework for clinicians to determine the genetic etiology and recurrence risks for individuals and families. DESIGN: One hundred ninety-five CPHD patients from the international GENHYPOPIT network were studied, according to their phenotype, for POU1F1, PROP1, LHX3, LHX4, and HESX1. PATIENTS: Patients selected had two pituitary hormone deficiencies or at least one deficiency with intracerebral malformations. RESULTS: Total prevalence of mutations was 13.3 and 52.4% in 20 patients with familial CPHD history. No mutation of HESX1 was observed in 16 patients harboring septooptic dysplasia. A mutation of LHX4 gene, previously reported, was found in one familial case from 39 patients bearing pituitary stalk interruption syndrome. In 109 patients without extrapituitary abnormalities, 20 had PROP1 mutations, including eight patients with a family history of CPHD. Among 20 patients without pituitary stalk interruption syndrome, no LHX3 gene defect was found, even with a neck rotation deficit. One POU1F1 gene defect was found in one patient presenting the rare postpubertal association of thyrotroph (TSH deficiency) and somatotroph (GH deficiency) deficits. CONCLUSIONS: Mutation of PROP1 gene remains the first to be looked for, and POU1F1 mutations should be sought in GH deficiency and TSH deficiency postpubertal population without extrapituitary malformations. Identification of gene defects allows early treatment of any deficit and prevention of their potentially fatal consequences. Genotyping appears highly beneficial at an individual and familial level.

Congenital isolated adrenocorticotropin deficiency: an underestimated cause of neonatal death, explained by TPIT gene mutations.

Tpit is a T box transcription factor important for terminal differentiation of pituitary proopiomelanocortin-expressing cells. We demonstrated that human and mouse mutations of the TPIT gene cause a neonatal-onset form of congenital isolated ACTH deficiency (IAD). In the absence of glucocorticoid replacement, IAD can lead to neonatal death by acute adrenal insufficiency. This clinical entity was not previously well characterized because of the small number of published cases. Since identification of the first TPIT mutations, we have enlarged our series of neonatal IAD patients to 27 patients from 21 unrelated families. We found TPIT mutations in 17 of 27 patients. We identified 10 different TPIT mutations, with one mutation found in five unrelated families. All patients appeared to be homozygous or compound heterozygous for TPIT mutations, and their unaffected parents are heterozygous carriers, confirming a recessive mode of transmission. We compared the clinical and biological phenotype of the 17 IAD patients carrying a TPIT mutation with the 10 IAD patients with normal TPIT-coding sequences. This series of neonatal IAD patients revealed a highly homogeneous clinical presentation, suggesting that this disease may be an underestimated cause of neonatal death. Identification of TPIT gene mutations as the principal molecular cause of neonatal IAD permits prenatal diagnosis for families at risk for the purpose of early glucocorticoid replacement therapy.