Conserved amino acid sequences confer nuclear localization upon the Prophet of Pit-1 pituitary transcription factor protein

Gene polymorphisms in PROP1 associated with growth traits in sheep

The PROP paired-like homeobox 1 (PROP1) gene encodes a protein that regulates growth and development in mammals. Possessing DNA-binding and transcriptional activation abilities, PROP1 is able to control the expression of crucial anterior pituitary hormones including growth hormone, thyroid-stimulating hormone, and prolactin. The objective of this study was to identify genetic variation in ovine PROP1 in 670 New Zealand Romney sheep. Three single nucleotide polymorphisms (SNPs) were detected, two of which located in intron 1 were novel (c.109+40 T>C and c.109+207C>T), whilst the one located in exon 1 (c.45A>G) had been previously reported. These SNPs were arranged into three haplotypic variants - A₁, B₁ and C₁. At each locus, all three genotypes were observed with frequencies in accordance with the Hardy-Weinberg Equilibrium. Association analysis revealed that the variant GG, CC and CC genotypes for c.45A>G, c.109+40 T>C and c.109+207C>T respectively were significantly associated with higher lamb tailing and weaning weights, and growth rate-to-weaning. The A₁ haplotype had a positive effect on tailing weight, weaning weight and growth rate, while the B₁ haplotype impacted growth traits negatively. These findings suggest that variations in ovine PROP1 could serve as potential genetic markers for use in marker-assisted selection and the breeding for animals with superior growth traits.

Novel Nucleotide Variations, Haplotypes Structure and Associations with Growth Related Traits of Goat AT Motif-Binding Factor (ATBF1) Gene

The AT motif-binding factor (ATBF1) not only interacts with protein inhibitor of activated signal transducer and activator of transcription 3 (STAT3) (PIAS3) to suppress STAT3 signaling regulating embryo early development and cell differentiation, but is required for early activation of the pituitary specific transcription factor 1 (Pit1) gene (also known as POU1F1) critically affecting mammalian growth and development. The goal of this study was to detect novel nucleotide variations and haplotypes structure of the ATBF1 gene, as well as to test their associations with growth-related traits in goats. Herein, a total of seven novel single nucleotide polymorphisms (SNPs) (SNP 1-7) within this gene were found in two well-known Chinese native goat breeds. Haplotypes structure analysis demonstrated that there were four haplotypes in Hainan black goat while seventeen haplotypes in Xinong Saanen dairy goat, and both breeds only shared one haplotype (hap1). Association testing revealed that the SNP2, SNP5, SNP6, and SNP7 loci were also found to significantly associate with growth-related traits in goats, respectively. Moreover, one diplotype in Xinong Saanen dairy goats significantly linked to growth related traits. These preliminary findings not only would extend the spectrum of genetic variations of the goat ATBF1 gene, but also would contribute to implementing marker-assisted selection in genetics and breeding in goats.

Pituitary transcription factors in the aetiology of combined pituitary hormone deficiency

The somatotropic axis is the central postnatal regulator of longitudinal growth. One of its major components--growth hormone--is produced by the anterior lobe of the pituitary, which also expresses and secretes five additional hormones (prolactin, thyroid stimulating hormone, follicle stimulating hormone, luteinizing hormone, adrenocorticotropic hormone). Proper development of the pituitary assures the regulation of critical processes such as metabolic control, puberty and reproduction, stress response and lactation. Ontogeny of the adenohypophysis is orchestrated by inputs from neighbouring tissues, cellular signalling molecules and transcription factors. Perturbation of expression or function of these factors has been implicated in the aetiology of combined pituitary hormone deficiency (CPHD). Mutations within the genes encoding for the transcription factors LHX3, LHX4, PROP1, and POU1F1 (PIT1) that act at different stages of pituitary development result in unique patterns of hormonal deficiencies reflecting their differential expression during organogenesis. In the case of LHX3 and LHX4 the phenotype may include extra-pituitary manifestations due to the function of these genes/proteins outside the pituitary gland. The remarkable variability in the clinical presentation of affected patients indicates the influence of the genetic background, environmental factors and possibly stochastic events. However, in the majority of CPHD cases the aetiology of this heterogeneous disease remains unexplained, which further suggests the involvement of additional genes. Identification of these factors might also help to close the gaps in our understanding of pituitary development, maintenance and function.

Identification of SNPs within the sheep PROP1 gene and their effects on wool traits

Regarding mutations of PROP1 (Prophet of POU1F1) gene significantly associating with combined pituitary hormone deficiency (CPHD) in human patients and animals, PROP1 gene is a novel important candidate gene for detecting genetic variation and growth, reproduction, metabolism traits selection and breeding. The aim of this study was to detect PROP1 gene mutation of the exon 1-3 and its association with wool traits in 345 Chinese Merino sheep. In this study, on the basis of PCR-SSCP and DNA sequencing methods, ten novel SNPs within the sheep PROP1 gene, namely, AY533708: g.45A>G resulting in Glu15Glu, g.1198A>G, g.1341G>C resulting in Arg63Ser, g.1389G>A resulting in Ala79Ala, g.1402C>T resulting in Leu84Leu, g.1424A>G resulting in Asn91Ser, g.1522C>T, g.1556A>T, g.1574T>C, g.2430C>G were reported. In addition, association analysis showed that three genotypes of P4 fragment were significantly associated with fiber diameter in the analyzed population (P=0.044). These results strongly suggested that polymorphisms of the PROP1 gene could be a useful molecular marker for sheep breeding and genetics through marker-assisted selection (MAS).

W194XProp1 and S156insTProp1, both of which have intact DNA-binding domain, show a different DNA-binding activity to the Prop1-binding element in human Pit-1 gene

Prop1 activates POU1F1 (Pit-1) gene expression, which in turn stimulates GH, PRL, TSHbeta and GHRH receptor gene expressions. Therefore the patients with Prop1 mutation show GH, PRL, and TSH deficiency. The mutation of Prop1 is a major abnormality causing combined pituitary hormone deficiency (CPHD). However, DNA-binding and activating functions of mutant Prop1 have not been examined fully because Prop1-binding elements (PBEs) in human POU1F1 gene were not identified until 2008. The aim of this study is to test DNA-binding and transcriptional activities of two mutant Prop1s (W194XProp1 and S156insTProp1, both of them were found in the patients with CPHD) whose mutation is located in putative transactivating domain but not in DNA-binding domain. W194XProp1 showed a marked DNA-binding to PBE as well as a consensus element of paired-like transcription factors (PRDQ9). Activating function for POU1F1 reporter genes expression was lost or decreased in W194XProp1 but still preserved for PRDQ9 reporter gene. S156insTProp1 did not bind PBE but bound PRDQ9. Consistent with the result, S156insTProp1 did not stimulate POU1F1 reporter gene but stimulated PRDQ9 reporter gene. These results support the inference that W194XProp1 is unable to increase POU1F1 gene expression by the defect of transactivating domain and that S156insTProp1 is unable to increase due to the loss of DNA-binding activity. DNA-binding domain that has been assumed is not sufficient to provide full DNA-binding activity of Prop1 and transactivating domain of Prop1 is likely to affect DNA binding to PBE.

Molecular analysis of novel PROP1 mutations associated with combined pituitary hormone deficiency (CPHD)

OBJECTIVE

Homozygous mutations in the gene encoding the pituitary transcription factor PROP1 are associated with combined pituitary hormone deficiency (CPHD) in both mice and humans with a highly variable phenotype with respect to the severity and time of initiation of pituitary hormone deficiency. We have ascertained three pedigrees with PROP1 mutations from a large cohort of patients with variable degrees of CPHD who were screened for mutations in PROP1.

RESULTS

Affected individuals from all three pedigrees were found to harbour novel PROP1 mutations. We have identified two siblings in one family who were homozygous for an intronic mutation (c.343-11C > G) that disrupts correct splicing resulting in the loss of exon 3 from the PROP1 transcript. Two siblings from a second, unrelated family are compound heterozygotes for two point mutations in the coding region, a missense mutation (p.R125W) that leads to impaired transcriptional activation, and a deletion of a single nucleotide (c.310delC) resulting in a frameshift and nonfunctional mutant protein. Additionally, we identified a homozygous deletion of the PROP1 locus in two patients born to consanguineous parents.

CONCLUSION

Mutations in PROP1 are a frequent cause of familial CPHD. We have described four novel mutations in PROP1 in 3 pedigrees, all resulting in PROP1 deficiency by different mechanisms. The phenotypic variation observed in association with PROP1 mutations both within and between families, together with the evolving nature of hormone deficiencies and sometimes changing pituitary morphology indicates a need for continual monitoring of these patients.

Comparative genomics reveals functional transcriptional control sequences in the Prop1 gene

Mutations in PROP1 are a common genetic cause of multiple pituitary hormone deficiency (MPHD). We used a comparative genomics approach to predict the transcriptional regulatory domains of Prop1 and tested them in cell culture and mice. A BAC transgene containing Prop1 completely rescues the Prop1 mutant phenotype, demonstrating that the regulatory elements necessary for proper PROP1 transcription are contained within the BAC. We generated DNA sequences from the PROP1 genes in lemur, pig, and five different primate species. Comparison of these with available human and mouse PROP1 sequences identified three putative regulatory sequences that are highly conserved. These are located in the PROP1 promoter proximal region, within the first intron of PROP1, and downstream of PROP1. Each of the conserved elements elicited orientation-specific enhancer activity in the context of the Drosophila alcohol dehydrogenase minimal promoter in both heterologous and pituitary-derived cells lines. The intronic element is sufficient to confer dorsal expansion of the pituitary expression domain of a transgene, suggesting that this element is important for the normal spatial expression of endogenous Prop1 during pituitary development. This study illustrates the usefulness of a comparative genomics approach in the identification of regulatory elements that may be the site of mutations responsible for some cases of MPHD.

Immunonegative "null cell" adenomas and gonadotropin (Gn) subunit (SUs) immunopositive adenomas share frequent expression of multiple transcription factors

The differentiation of pituitary cells and human pituitary adenomas follow three cell lineages: GH-PRL-TSH, ACTH, and FSH/LH, which are regulated by a combination of various transcription factors and co-factors. We have used RT-PCR and immunohistochemistry to show that immunonegative, "null cell" adenomas are equipped with multiple transcription factors and co-factors. The "null cell" adenomas showed similar frequencies of transcription factors as did the gonadotropin subunit (GnSU)-positive adenomas, with the exception that there were fewer instances of SF1 in the former. We speculate, therefore, that null cell adenomas and GnSU-positive adenomas share common molecular mechanisms in functional differentiation, even though the former do not produce hormones. From the high frequency of various transcription factors, we also speculate that both null cell adenomas and GnSU-positive adenomas are derived from "committed" pituitary progenitor stem cells. The questions, why a certain proportion of these pituitary tumor groups lack hormone production and why they are molecularly more committed to Gn transcription, remain to be further investigated.

An uncommon phenotype with familial central hypogonadism caused by a novel PROP1 gene mutant truncated in the transactivation domain

CONTEXT

PROP1 gene mutations are usually associated with childhood onset GH and TSH deficiencies, whereas gonadotroph deficiency is diagnosed at pubertal age.

OBJECTIVES

We report a novel PROP1 mutation revealed by familial normosmic hypogonadotropic hypogonadism. We performed in vitro transactivation and DNA binding experiments to study functional consequences of this mutation.

SETTING

Three brothers were followed in the Department of Endocrinology of a French university hospital.

PATIENTS

These patients from a consanguineous kindred were referred for cryptorchidism and/or delayed puberty.

RESULTS

Initial investigations revealed hypogonadotropic hypogonadism. One of the patients had psychomotor retardation, intracranial hypertension, and minor renal malformations. The brothers reached normal adult height and developed GH and TSH deficiencies after age 30. A novel homozygous nonsense mutation (W194X) was found in the PROP1 gene, indicating that the protein is truncated in its transactivation domain. Transfection studies confirmed the deleterious effect of this mutation, whose transactivation capacity was only 34.4% of that of the wild-type. Unexpectedly altered DNA-binding properties suggested that the C-terminal end of the factor plays a role in protein-DNA interaction.

CONCLUSIONS

PROP1 mutations should be considered among the growing number of genetic causes of initially isolated hypogonadotropic hypogonadism. This report extends the phenotype variability associated with PROP1 mutations.