PubMed Health⌕ Search

Biomedical subjects

R W Pfäffle

Publications and source records attributed to R W Pfäffle.

6 recordsLinked to original sources
PubMed1998

Mutations in PROP1 cause familial combined pituitary hormone deficiency.

Combined pituitary hormone deficiency (CPHD) in man denotes impaired production of growth hormone (GH) and one or more of the other five anterior pituitary hormones. Mutations of the pituitary transcription factor gene POU1F1 (the human homologue of mouse Pit1) are responsible for deficiencies of GH, prolactin and thyroid stimulating hormone (TSH) in Snell and Jackson dwarf mice and in man, while the production of adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH) and follicle stimulating hormone (FSH) is preserved. The Ames dwarf (df) mouse displays a similar phenotype, and appears to be epistatic to Snell and Jackson dwarfism. We have recently positionally cloned the putative Ames dwarf gene Prop1, which encodes a paired-like homeodomain protein that is expressed specifically in embryonic pituitary and is necessary for Pit1 expression. In this report, we have identified four CPHD families with homozygosity or compound heterozygosity for inactivating mutations of PROP1. These mutations in the human PROP1 gene result in a gene product with reduced DNA-binding and transcriptional activation ability in comparison to the product of the murine df mutation. In contrast to individuals with POU1F1 mutations, those with PROP1 mutations cannot produce LH and FSH at a sufficient level and do not enter puberty spontaneously. Our results identify a major cause of CPHD in humans and suggest a direct or indirect role for PROP1 in the ontogenesis of pituitary gonadotropes, as well as somatotropes, lactotropes and caudomedial thyrotropes.

Adolescent↗
PubMed1997

GH and TSH deficiency.

Hypothyroidism is a recognised complication of GH therapy in GH deficient children. The mechanisms involved include direct effects on thyroid function but also result from the close interrelationship of pituitary cell-lines that differentiate during embryonic development of the anterior pituitary gland. Among numerous pituitary transcriptionfactors that orchestrate pituitary organogenesis Pit-1 was the first to be recognised and is the most extensively studied. Mutations in the Pit-1 gene account for a form of combined pituitary hormone deficiency for GH, Prolactin (Prl) and TSH (CPHD). Despite the variability of the clinical presentation of this syndrome at the time of initial diagnosis, all forms finally result in severe retardation of growth and development due to GH-deficiency and hypothyroidism. More than half of the families with a combined pituitary hormone deficiency have not disclosed any Pit-1 abnormalities. Evidence is accumulating that Prop-1, a transcriptionfactor expressed temporarily in the fetal anterior pituitary, could be a candidate for patients with a Pit-1 phenotype without any Pit-1 gene abnormalities.

DNA-Binding Proteins↗
PubMed1993

Genetics of growth hormone gene expression.

The regulation of pituitary GH gene expression depends on binding of transcriptional activation proteins to cis-active DNA sequences preceding the GH-1 gene. The POU homeodomain protein Pit-1 is found in the nuclei of somatotrophs, lactotrophs and thyrotrophs. It fosters differentiation of these pituitary cell types and is required for hormone production by mature cells. In theory, defects in GH secretion can be caused by mutations in the GH-1 promoter sequence or in the gene encoding Pit-1. In the former case, deficiency would be limited to GH, and in the latter deficiencies extend to prolactin (Prl) and thyrotropin (TSH) as well as to GH. Both the Pit-1 gene and the GH-1 gene have been examined in children with extreme growth failure. Studies of kindreds with GH, Prl and TSH deficiency have disclosed a variety of mutations in the Pit-1 gene. These include nonsense mutations, missense mutations that diminish binding and transcriptional activation, and also mutations that appear to increase promoter binding while eliminating transcriptional activation. This latter class of mutation exerts a dominant negative effect in vivo as well as in vitro. There are many examples of deletions in the GH-1 coding sequence. Some are very large and cause the loss of GH-1, chorionic somatomammotropin and placental GH genes. Others are very small, involving only 1 or 2 bases. They produce frameshifts and premature stop signals. All types produce complete deficiency of GH, but antibody development during treatment has proven to be quite variable. The cDNA for the GH-releasing hormone receptor has recently been cloned and sequenced.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Mutation of the POU-specific domain of Pit-1 and hypopituitarism without pituitary hypoplasia.

A point mutation in the POU-specific portion of the human gene that encodes the tissue-specific POU-domain transcription factor, Pit-1, results in hypopituitarism, with deficiencies of growth hormone, prolactin, and thyroid-stimulating hormone. In two unrelated Dutch families, a mutation in Pit-1 that altered an alanine in the first putative alpha helix of the POU-specific domain to proline was observed. This mutation generated a protein capable of binding to DNA response elements but unable to effectively activate its known target genes, growth hormone and prolactin. The phenotype of the affected individuals suggests that the mutant Pit-1 protein is competent to initiate other programs of gene activation required for normal proliferation of somatotrope, lactotrope, and thyrotrope cell types. Thus, a mutation in the POU-specific domain of Pit-1 has a selective effect on a subset of Pit-1 target genes.

Animals↗
PubMedDate not supplied

Pit-1 and pituitary function.

Several patients with pituitary dwarfism and a variable degree of hypothyroidism have been shown to have mutations in their Pit-1 gene. Pit-1 activates transcription of the growth hormone and prolactin genes and is necessary for the control of the beta-TSH gene transcription. The various mutations have different effects on the DNA binding and transactivating properties of Pit-1. Multiple pituitary hormone deficiency due to Pit-1 mutations is inherited either dominantly or recessively depending on the DNA binding properties of the mutant protein. The comparison of pheno- and genotype in patients with multiple pituitary hormone deficiency provides some insight into the function of the Pit-1 protein.

Animals↗