This Article Abstract Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Vallette-Kasic, S. Articles by Brue, T. Search for Related Content PubMed PubMed Citation Articles by Vallette-Kasic, S. Articles by Brue, T.

Differential Regulation of Proopiomelanocortin and Pituitary-Restricted Transcription Factor (TPIT), a New Marker of Normal and Adenomatous Human Corticotrophs

Laboratoire des Interactions Cellulaires Neuro-Endocriniennes (S.V.-K., A.E., T.B.), Unité Mixte de Recherche 6544, Centre National de la Recherche Scientifique; Laboratoire des Interactions Fonctionnelles en Neuroendocrinologie (M.G.), Université de la Méditerranée, Institut Fédératif de Recherche Jean-Roche, Faculté de Médecine Nord, 13926 Marseille, France; Laboratoire d’Anatomie Pathologique et de Neuropathologie (D.F.-B.), Department of Neurosurgery (H.D., F.G.), and Department of Endocrinology (S.V.-K., T.B.), Centre Hospitalo-Universitaire Timone, 13385 Marseille, France; and Laboratoire de Génétique Moléculaire (A.-M.P., J.D.), Institut de Recherche Clinique de Montréal, Canada

Address all correspondence and requests for reprints to: Thierry Brue, M.D., Ph.D., Hopital de la Timone, 264 rue St Pierre, 13385 Marseille Cedex 5, France. E-mail: Thierry.Brue{at}mail.ap-hm.fr.

	Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
Since the identification of the pituitary-restricted transcription factor Tpit, a novel T-box factor that is only present in mouse in the two pituitary proopiomelanocortin (POMC)-expressing lineages, no information was available on its pattern of expression in human pituitary. We investigated by immunohistochemistry and in situ hybridization the expression of TPIT in normal human anterior pituitary tissue and in several types of human pituitary adenomas (n = 52).

TPIT expression was restricted to the nucleus of normal or adenomatous human corticotroph cells. No specific TPIT immunostaining was detectable in all prolactin (PRL)-, GH-, or gonadotropin-secreting adenomas. In situ hybridization studies demonstrated that TPIT transcripts were coexpressed with POMC mRNA in both secreting and silent corticotroph adenomas, and in normal corticotrophs, whereas TPIT mRNA was not detectable in other types of pituitary adenomas. Unlike POMC, TPIT was not up-regulated by adrenalectomy in rats and did not seem down-regulated in the normal pituitary adjacent to human corticotroph microadenomas.

TPIT is the only currently known transcription factor selectively expressed in human normal and adenomatous corticotrophs. In human and experimental models, TPIT and its target gene POMC were thus differentially regulated by glucocorticoids. Moreover, TPIT represents a new marker of POMC-expressing pituitary cells.

	Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
THE REGULATED PRODUCTION of pituitary hormones requires the concerted action of multiple transcription factors acting on the promoters or enhancers of hormone-coding genes. In addition to the general transcription factors, widely expressed in various tissues, many of these proteins are restricted to the pituitary or to one of its sublineages. A number of these cell-restricted transcription factors first play a role in the control of morphogenesis, lineage differentiation, and/or proliferation, and are then recruited to regulate cell-specific gene expression. Thus, a combination of cell-specific and hormone regulated transcription factors cooperate to integrate the developmental and endocrine signals necessary for the homeostatic production of pituitary hormones (1). In the corticotrope lineage, in addition to Pitx1 and Pitx2, pituitary-specific transcription of proopiomelanocortin (POMC) requires basic helix-loop-helix (bHLH) heterodimers containing a neurogenic bHLH-like NeuroD1/ß2, and a novel transcription factor present only in POMC-expressing cells, called Tpit (2). Interaction between these murine factors is critical for cell-specific transcription of the POMC gene and for integration of endocrine signals that also regulate POMC expression.

Tpit was first identified as a partner of Pitx1 on the POMC promoter (2). This protein, also described as Tbx19 (3), belongs to the T-box family of transcription factors named after Brachyury or Tail (T) (4). It was recently shown to play a key role in the differentiation of the corticotroph lineage (2, 5). Genes encoding T-box factors are present in all vertebrates, and several diseases have been associated with mutations of such genes in humans (6, 7, 8).

In embryonic mouse pituitary, Tpit was selectively expressed from embryonic day (e) 12.5 in the nucleus of POMC-expressing cells of the anterior lobe, and from e15.5 in the melanotrophs of the intermediate lobe. In the adult murine pituitary, colocalization experiments showed that anterior lobe Tpit is only expressed in corticotrophs, whereas Tpit is present in all cells of the intermediate lobe (melanotrophs) (2). Interestingly, expression of Tpit was not found in POMC-positive hypothalamic neurons (2).

Mutations of TPIT have recently been identified in patients with isolated ACTH deficiency (2, 9), confirming the key role of TPIT in corticotroph differentiation and POMC regulation in humans, which was suggested by its spatiotemporal pattern of expression in mouse. This finding, however, did not provide any information on the postnatal expression of TPIT in human pituitary, as substantial inter-specific differences have been found for pituitary transcription factors (1). Indeed, since the identification of Tpit in murine pituitary, no information was available on its pattern of expression in human pituitary. We thus investigated in the present study, both by immunohistochemistry and in situ hybridization, the expression of TPIT in normal human anterior pituitary tissue, and in several types of human pituitary adenomas. We also studied in human and experimental models the regulation of TPIT by glucocorticoids.

	Materials and Methods

Top Abstract Introduction Materials and Methods Results Discussion References

 
Animals

Male Sprague Dawley rats (weighing 180–200 g) were purchased from the Centre d’élevage R. Janvier (le Genest St. Isle, France). They were housed in our laboratory under controlled temperature (22–24 C) and a constant 12-h light, 12-h dark cycle. They had free access to standard rat chow and tap water. Bilateral adrenalectomy or sham operation (n = 5 in each group) was performed under ether anesthesia using a dorsal approach. Adrenalectomized animals were offered 9% NaCl as drinking solution. Rats were killed by decapitation 1 wk later. Pituitaries were carefully removed, immediately frozen on dry ice, and stored at -80 C until sectioning. Completeness of the removal of the adrenal glands was verified by visual examination.

Tissues

Nontumoral pituitary tissue was obtained as part of the surgical resection of 11 different microprolactinomas, and characterized by standard histological and immunohistochemical methods as nonadenomatous tissue surrounding an adenoma. The surgical approach aiming at improving the postoperative results by taking out a slice of normal pituitary at the periphery of the adenoma has been routinely performed in our neurosurgical department since 1987, and no change was made to this procedure because of the present study (10).

Adenomatous pituitary tissue was obtained by transsphenoidal surgery in 52 patients (Tables 1 and 2). They were classified using clinical, biochemical, morphological, and immunohistochemical data. Tumor specimens included 18 ACTH-producing (corticotroph) microadenomas (largest diameter < 10 mm), 12 corticotroph macroadenomas (10 mm) (Table 1), 5 prolactinomas (1 macroadenoma), 7 GH-secreting adenomas (6 macroadenomas), 7 gonadotroph macroadenomas, and 3 null cell macroadenomas (Table 2). Finally, a fragment from a bronchial ectopic ACTH- and CRH-secreting neuroendocrine tumor was also obtained at surgery during the course of the present study in a patient presenting with Cushing’s syndrome (Table 1).

All tumor specimens obtained at surgery were immediately fixed in 10% formalin and embedded in paraffin. They were studied by the same pathologist (D.F.B.). The sections were stained by Herlant’s tetrachrome and hematoxylin-phloxin safran and used for immunohistochemistry. The following primary antibodies were used: ACTH (polyclonal, prediluted, Bioadvance, Philadelphia, PA), ßLH, ßFSH, ßTSH (monoclonal, 1/200, Immunotech, Marseille, France), PRL, -subunit (monoclonal, 1/100, Immunotech), GH (polyclonal, 1/1000, Dakopatts, Stockholm, Sweden). In addition, a monoclonal anti-ACTH antibody (J. Drouin, Institut de Recherche Clinique de Montréal, Montréal, Canada) was used for double labeling. The polyclonal anti-Tpit antibody (J. Drouin) directed against the entire murine Tpit sequence was used at 1/200.

Automate (Ventana, Illkirch, France) immunoperoxidase detection of the antigens described above was performed on serial 4-µm-thick paraffin sections in all tissues. Controls included omission of primary antibody and irrelevant IgG. Revelation was done using aminoethyl carbazole as substrate. For double labeling performed in two normal pituitaries and two corticotroph adenomas, anti-Tpit antibody (1/200) was applied first on deparaffinized sections during 1 h, rinsed in PBS, followed by biotinylated antirabbit antibody (30 min). Revelation was done using aminoethyl carbazole as substrate. Then monoclonal anti-ACTH antibody was applied (1 h), the sections were rinsed in PBS and incubated with the biotinylated antimouse IgG (30 min). Revelation was performed using SG (blue/gray) as substrate. For double labeling, all reagents were from Vector Laboratories (AbCys SA, Paris, France).

In situ hybridization

Tumor fragments were frozen on dry ice immediately after surgical removal and kept at -80 C until sectioning. Twelve-micrometer sections were cut in a cryostat, mounted on gelatin-coated slides, processed, and singly or double labeled as previously described (11). The TPIT probe was a 1.6-kb EcoRV fragment of the human TPIT gene (3), subcloned into pbluescript, linearized with XbaI (antisense probe) or with HindIII (sense probe), and labeled with ³⁵S-uridine triphosphate (UTP) (Perkin-Elmer, Courtaboeuf, France). The POMC probe was a 397-bp AluI fragment of the rat POMC gene (12) subcloned into PSP64 (kindly provided by Dr. J. Roberts, Mt. Sinai School of Medicine, New York, NY), linearized with BamHI, and labeled either with ³⁵S-UTP (for single labeling of rat anterior pituitary sections) or with UTP coupled to digoxigenin (Roche Molecular Biochemicals, Meylan, France) for double labeling. After hybridization and washing, the POMC probe was revealed by subsequent incubations with antiserum antidigoxigenin coupled to peroxidase (Roche Molecular Biochemicals) and tyramide coupled to fluorescein (Perkin-Elmer). Slides were exposed to x-ray films (BIOMAX MR, Kodak, Le Pontet, France) concomitantly with ¹⁴C standards (Amersham, Saclay, France), subsequently dipped in nuclear emulsion (1:1 in water, K5, Ilford, Saint-Priest, France) and exposed for 24–72 h. After development, singly labeled sections were counterstained with hematoxylin-eosin. POMC and TPIT hybridization signals in rat pituitaries were quantified on the film autoradiograms using the NIH Image software (13) and the ¹⁴C standards.

Brightfield images were captured with a color charge-coupled device camera (Coolsnap, Princeton Instruments, Paris, France) attached to a Leica Corp. (Rueil-Malmaison, France) microscope, and digitized. Composites were formed within Adobe Photoshop (Adobe, San Jose, CA). Brightness and contrast were altered to generate photographic quality prints.

	Results

Top Abstract Introduction Materials and Methods Results Discussion References

 
Unlike POMC, Tpit is not up-regulated by glucocorticoid deprivation in rats

In the rat, Tpit mRNA was expressed both in the anterior and intermediate pituitary lobes. Surgical adrenalectomy induced the expected POMC up-regulation in the anterior lobe and a lack of change in the intermediate lobe, whereas no significant change was observed in Tpit mRNA levels in both lobes (Fig. 1).

View larger version (79K): [in this window] [in a new window]   FIG. 1. Glucocorticoid regulation of TPIT and POMC gene expression in the rat pituitary. Pituitary sections obtained from 1 wk adrenalectomized (ADX) or sham-operated (Sham) rats were hybridized as described in Materials and Methods. Upper panel, Macroautoradiographic views obtained after 1 d (POMC) or 10 d (TPIT) of exposure. Scale bar, 1 mm. POMC and TPIT hybridization signals in rat anterior and intermediate pituitary lobes were quantified on the film autoradiograms using the NIH Image software (12 ) and 14C standards. Lower panel, Results of this semiquantitative analysis. Note that the scale for TPIT mRNA levels is expressed in nCi/g, whereas the scale for POMC mRNA is expressed in nCi/g x 10-2. *, P = 0.0002 vs. Sham.

In human tissues, immunohistochemical studies showed that TPIT expression was restricted to the nucleus of normal corticotroph cells (Fig. 2A). Colocalization studies showed at the protein level that TPIT was coexpressed with ACTH in normal corticotroph cells (Fig. 2B) and that TPIT transcripts were coexpressed with POMC mRNA in normal corticotrophs (Fig. 2C). In situ hybridization studies demonstrated that TPIT mRNA was expressed in normal human pituitary (Fig. 2D).

View larger version (79K): [in this window] [in a new window]   FIG. 2. TPIT expression in normal human corticotrophs. A, Nonneoplastic pituitary tissue obtained as described in Materials and Methods was immunolabeled with anti-TPIT antibody. All corticotroph cells (identified on serial sections counterstained with Herlant’s tetrachrome) showed TPIT immunoreactivity within their nuclei whereas other cells did not express TPIT. B, Double labeling demonstrated in the same normal corticotroph cell, TPIT immunoreactivity within nucleus (red) and ACTH immunostaining in the cytoplasm (blue/gray), as exemplified in cells indicated by arrows. C, Colocalization of TPIT and POMC mRNA in normal human anterior pituitary by double in situ hybridization. Sections were hybridized with both the radioactive Tpit probe and the nonradioactive POMC probe, as described in Material and Methods. Silver grain clusters (inverted to yellow for better visualization and representing the hybridized radiolabeled Tpit probe) overlaid green fluorescent signal (representing the hybridized nonradioactive POMC probe), demonstrating colocalization of both mRNA species. Isolated silver grains overlaying non fluorescent areas represent the background of both the hybridization and the microautoradiography procedures. Scale bar, 20 µm. D, TPIT mRNA is expressed in normal human anterior pituitary; exposure time was 3 d. Scale bar, 20 µm.

In corticotroph adenomas (Fig. 3A), TPIT expression was overall found in 22/26 (85%) of the tumors examined by immunochemistry (Table 1). A positive TPIT nuclear immunostaining was found in all 15 corticotroph microadenomas tested (Fig. 3B). In average, 64.6% of the cells (extremes: 15–100%) were positive. Eight of 12 (67%) macroadenomas were found positive for TPIT, and 35% of the cells (extremes: 5–80%) exhibited a positive nuclear staining. Among the four TPIT negative cases, one was a silent corticotroph macroadenoma, and three were partially fibrous and/or necrotic fragments. Double labeling demonstrated colocalization of TPIT and ACTH proteins in adenomatous corticotroph cells (data not shown).

View larger version (110K): [in this window] [in a new window]   FIG. 3. TPIT expression in corticotroph (A–F) or noncorticotroph (G–H) pituitary adenomas. A, Typical feature of a corticotroph adenoma stained by Herlant’s tetrachrome: large and basophilic cells with round nucleus. B, Immunohistochemical analysis of a corticotroph adenoma: all tumor cells strongly expressed TPIT within their nuclei. C–F, Microautoradiographic views of in situ hybridization for TPIT mRNA in corticotroph adenomas. C and D, Secreting corticotroph microadenoma hybridized with Tpit antisense (C) or sense (D) probe. Note the lack of signal in D, demonstrating the specificity of the probe and of the hybridization procedure. Exposure time was 1 d. E, Colocalization of TPIT and POMC mRNA in a secreting corticotroph adenoma by double in situ hybridization, as detailed in the legend to Fig. 2C. F, Microautoradiographic view of in situ hybridization for TPIT mRNA in a corticotroph macroadenoma. Exposure time was 3 d. Scale bar, 20 µm. G, Lack of immunohistochemical TPIT protein revelation in a microprolactinoma. Prolactinoma cells (asterisk) did not express TPIT, in contrast to normal pituitary tissue at the periphery of the adenoma where TPIT expression was observed in some cells (corticotrophs). H, Lack of TPIT mRNA detection in a somatotroph adenoma, after a 3-d exposure. Scale bar, 20 µm.

In situ hybridization studies demonstrated that TPIT transcripts were detectable in all four corticotroph adenomas tested (two microadenomas and two macroadenomas) (Fig. 3, C, E, and F, and Table 1), and that TPIT mRNA was coexpressed with POMC mRNA in both secreting (n = 3) and silent (n = 1) corticotroph adenomas (Fig. 3E).

No specific TPIT immunostaining was found in all PRL- (n = 5), GH- (n = 6), gonadotropin- (n = 6) secreting adenomas tested (Table 2 and Fig. 3G). This finding was confirmed at the mRNA level by in situ hybridization in patients presenting with GH- (n = 1) or gonadotropin- (n = 1) producing adenomas (Table 2 and Fig. 3H).

Finally, immunohistochemistry and in situ hybridization showed that TPIT was not present in the fragment from bronchial ectopic ACTH-secreting neuroendocrine tumor (Table 1).

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
The T-box transcription factor Tpit had first been identified in mouse as a partner of Pitx homeoproteins for the regulation of POMC gene expression in corticotrophs and melanotrophs. Its pattern of expression before and after birth, restricted to POMC expressing cells of the anterior pituitary gland, suggested a role in corticotroph differentiation that was confirmed by gain of function experiments (2), and more recently by gene inactivation studies (5). Moreover, the likely involvement of its human ortholog TPIT in the differentiation of functional corticotroph cells in man was deduced from the identification of TPIT gene alterations in two unrelated children presenting with congenital isolated ACTH deficiency (2). As no data were available on the expression of TPIT in human adult pituitary, we studied, both at protein and mRNA levels, the expression of this factor in normal and adenomatous pituitary tissue surgically removed by transsphenoidal approach. Using an antibody raised against the entire murine Tpit sequence, immunohistochemical studies found TPIT to colocalize with ACTH positive corticotrophs in normal pituitary tissue. The specificity of this finding was confirmed by in situ hybridization showing the presence of TPIT mRNA in the same cells that expressed the ACTH precursor POMC. Moreover, in adenomatous pituitary tissue, a specific TPIT immunostaining was only found in ACTH positive cells, and TPIT mRNA was detected by in situ hybridization only in cells from POMC-expressing adenomas, as evidenced by colocalization experiments. Interestingly, no TPIT protein or mRNA was detected in all of the noncorticotroph pituitary adenomas tested. These results clearly differ from the pattern of transcriptional and translational expression of several transcription factors involved in corticotroph differentiation. The bHLH transcription factor NeuroD1/ß2 is restricted in its pituitary expression to corticotrophs and the onset of its expression closely precedes that of POMC (14). This factor specifically binds to the POMC promoter and activates transcription of the POMC gene (14). Indeed NeuroD1 was found mainly albeit not exclusively in normal human corticotrophs by immunochemistry (14). Using RT-PCR, a more sensitive approach, as well as immunohistochemical techniques, it was shown to be expressed in all 10 corticotroph adenomas tested but also in all other types of pituitary adenomas, especially null cell and gonadotroph adenomas (15). The tissue restricted factors Pitx1 and Pitx2 of the paired subfamily are expressed early during ontogenesis of the anterior pituitary, throughout its development and in the adult gland. In corticotrophs, transcription of the POMC gene involves physical interaction between Pitx1 and bHLH dimers containing NeuroD1 (14, 16). By Northern blot analysis, Pitx1 and Pitx2 mRNAs were present in normal adult and fetal human pituitaries. In a series of 60 pituitary adenomas, Pitx1 was found in all types of tumors, particularly in gonadotroph adenomas; and Pitx2 was preferentially expressed in tumors of the gonadotroph lineage, at lower levels in lactotroph and thyrotroph adenomas, but not in adenomatous somatotrophs and corticotrophs (17). We thus demonstrate in this paper that TPIT is the only currently known transcription factor selectively expressed in human normal and adenomatous corticotrophs.

A comparable specificity was found for the POU domain transcription factor Pit-1 that was found to be selectively expressed in the cell types whose differentiation and regulation it controls. Many investigators indeed have examined Pit-1 mRNA expression in human pituitaries using a variety of methods. These studies have selectively localized Pit-1 to GH, PRL, and TSH tumors. Some null cell adenomas were also found to express Pit-1 mRNA, whereas gonadotroph and corticotroph tumors had absent or very low levels of Pit-1 mRNA transcripts (18). The paired-like homeodomain pituitary transcription factor Prop1 was first considered as involved in the differentiation of somatotroph, lactotroph, thyrotroph, and gonadotroph lineages (19). However, it was present in all types of human pituitary adenomas including corticotrophs (20), suggesting a possible role in this latter cell type. This hypothesis is supported by observations of human PROP1 mutations that were found to be associated with corticotroph deficiency (21) and more recently by phenotypic peculiarities of the Prop1 null allele mice (22). Indeed, these mutants exhibit a temporal delay in differentiation and a reduction of the number of corticotroph and gonadotroph cells, in addition to complete absence of GH, PRL, and TSH cells.

Another interesting observation was that of a differential regulation of TPIT and its target gene POMC. Indeed in the anterior pituitary of adrenalectomized rats, POMC, but not Tpit, was up-regulated by corticosterone deprivation. In the opposite situation, despite hypercortisolism induced by a corticotroph microadenoma, TPIT expression was still present in presumably normal corticotroph cells surrounding the adenoma. Under two distinct conditions in both animal and human models, Tpit expression thus did not parallel that of its target gene POMC. Similarly, in terms of patterns of expression, Tpit has been shown to be present in POMC positive murine anterior pituitary corticotrophs and melanotrophs, and not in hypothalamic neurons that, however, also expressed POMC (2). In human tissues, we found that both TPIT and POMC were coexpressed in normal or adenomatous anterior pituitary corticotrophs, whereas only POMC was present in an ectopic ACTH-producing endocrine tumor, suggesting that the dedifferentiation process observed in such a tumor was unlikely to be dependent on TPIT. The latter finding, however, has to be confirmed on a larger number of specimens. In view of its role in corticotroph differentiation and proliferation during anterior pituitary ontogenesis and of its almost constant expression in corticotroph adenomas, a potential contribution of TPIT to the pathogenesis of this type of well-differentiated tumor cannot be ruled out.

These results indicate that TPIT is selectively expressed in both normal and adenomatous corticotrophs in humans, and thus represents a new marker of POMC-expressing pituitary cells. TPIT and its target gene POMC are differentially regulated in ACTH-producing tissues. In contrast to other pituitary transcription factors that are characterized by a broader pattern of expression in different anterior pituitary cell lineages such as Pitx1/2 or NeuroD1, TPIT thus belongs to a category of highly cell type specific transcription factors that also includes Pit-1.

	Footnotes

 
Abbreviations: bHLH, Basic helix-loop-helix; e, embryonic day; Pit-1, pituitary transcription factor 1, now POU1F1 in official nomenclature; POMC, proopiomelanocortin; PRL, prolactin; PROP1, prophet of Pit-1; Tpit, pituitary-restricted transcription factor; UTP, uridine triphosphate.

Received December 9, 2002.

Accepted March 12, 2003.

	References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Dattani M, Robinson I 2000 The molecular basis for developmental disorders of the pituitary gland in man. Clin Genet 57:337–346[CrossRef][Medline]
2. Lamolet B, Pulichino A, Lamonerie T, Gauthier Y, Brue T, Enjalbert A, Drouin J 2001 A pituitary cell-restricted T box factor, Tpit, activates POMC transcription in cooperation with Pitx homeoproteins. Cell 104:849–859[CrossRef][Medline]
3. Yi C, Terrett J, Li Q, Ellington K, Packham E, Amstrong-Buisseret L, McClure P, Slingsby T, Brook J 1999 Identification, mapping and phylogenomic analysis of four new human members of the T-box gene family: EOMES, TBX6, TBX18, and TBX19. Genomics 55:10[CrossRef][Medline]
4. Herrmann B, Labeit S, Poustka K, King T, Lehrach H 1990 Cloning of the T gene required in mesoderm formation in the mouse. Nature 343:617–622[CrossRef][Medline]
5. Pulichino AM, Vallette-Kasic S, Tsai P-Y, Couture C, Gauthier Y, Drouin J 2003 Tpit determines alternate fates during pituitary cell differentiation. Genes Dev 17:738–747[Abstract/Free Full Text]
6. Merscher S, Funke B, and Epstein J 2001 TBX1 is responsible for cardiovascular defects in velo-cardio-facial/DiGeorge syndrome. Cell 104:619–629[CrossRef][Medline]
7. Bamshad M, Le T, Watkins W 1999 The spectrum of mutations in TBX3: genotype/phenotype relationship in ulnar-mammary syndrome. Am J Hum Genet 64:1550–1562[CrossRef][Medline]
8. Li Q, Newbury-Ecob R, and Terrett J 1997 Holt-Oram syndrome is caused by mutations in TBX5, a member of the Brachyury (T) gene family. Nat Genet 15:21–29[CrossRef][Medline]
9. Pulichino AM, Vallette-Kasic S, Couture C, Gauthier Y, Brue T, David M, Malpuech G, Deal C, Van Vliet G, De Vroede M, Riepe FG, Partsch CJ, Sippell WG, Berberoglu M, Atasay B, Drouin J 2003 Human and mouse TPIT gene mutations cause early onset pituitary deficiency. Genes Dev 17:711–716[Abstract/Free Full Text]
10. Grisoli F, Brue T, Graziani N, Costa R, Trouillas J, Begou D, Jaquet P 1990 Enlarged adenomectomy for enclosed prolactinomas: a preliminary study of 26 cases. Acta Neurochir (Wien) 103:92–98
11. Grino M, Zamora A 1998 An in situ hybridization histochemistry technique allowing simultaneous visualization by the use of confocal microscopy of three cellular mRNA species within individual neurons. J Histochem Cytochem 46:753–759[Abstract/Free Full Text]
12. Drouin J, Chamberland M, Charron J, Jeannotte L, Nemer M 1985 Structure of the rat proopiomelanocortin (POMC) gene. FEBS Lett 193:54–58[CrossRef][Medline]
13. Rasband W, Bright D 1995 NIH image: a public domain image processing program for the Macintosh. Microbeam Anal Soc J 4:137–149
14. Poulin G, Turgeon B, Drouin J 1997 NeuroD1/ß2 contributes to cell-specific transcription of the proopiomelanocortin gene. Mol Cell Biol 17:6673–6682[Abstract]
15. Oyama K, Sanno N, Teramoto A, Osamura R 2001 Expression of NeuroD1 in human normal pituitaries and pituitary adenomas. Mod Pathol 14:892–899[Medline]
16. Poulin G, Lebel M, Chamberland M, Paradis F, Drouin J 2000 Specific protein:protein interaction between basic helix-loop-helix transcription factors and homeoproteins of the Pitx family. Mol Cell Biol 20:4826–4837[Abstract/Free Full Text]
17. Pellegrini-Bouiller I, Manrique C, Gunz G, Grino M, Zamora A, Figarella-Branger D, Grisoli F, Jaquet P, Enjalbert A 1999 Expression of the members of the Ptx family of transcription factors in human pituitary adenomas. J Clin Endocrinol Metab 84:2212–2220[Abstract/Free Full Text]
18. Lloyd RV, Osamura RY 1997 Transcription factors in normal and neoplastic pituitary tissues. Microsc Res Tech 39:168–181[Medline]
19. Sornson M, Wu W, Dasen J, Flynn S, Norman D, O’Connell S, Gukovsky I, Carriere C, Ryan A, Miller A, Zuo L, Gleiberman AS, Andersen B, Beamer WG, Rosenfeld MG 1996 Pituitary lineage determination by the prophet of Pit-1 homeodomain factor defective in Ames dwarfism. Nature 384:327–333[CrossRef][Medline]
20. Usui T, Nakamura Y, Mizuta H, Murabe H, Muro S, Suda M, Tanaka I, Shimatsu A, Nakao K 2000 Functional significance of Prop-1 gene expression in pituitary adenomas. Endocr J 47:S85–S89
21. Vallette-Kasic S, Barlier A, Teinturier C, Diaz A, Manavela M, Berthezene F, Bouchard P, Chaussain J, Brauner R, Pellegrini-Bouiller I, Jaquet P, Enjalbert A, Brue T 2001 PROP1 gene screening in patients with multiple pituitary hormone deficiency reveals two sites of hypermutability and a high incidence of corticotroph deficiency. J Clin Endocrinol Metab 86:4529–4535[Abstract/Free Full Text]
22. Nasonkin I, Ward R, Paine R, Camper S Prophet of Pit1 (Prop1) knockout mice exhibit severe pituitary hypoplasia and poor viability due to respiratory distress. Program of the 84th Annual Meeting of The Endocrine Society, San Francisco, CA, 2002, p 339 (Abstract P2-73)

This article has been cited by other articles:

				T. Tateno, H. Izumiyama, M. Doi, T. Yoshimoto, M. Shichiri, N. Inoshita, K. Oyama, S. Yamada, and Y. Hirata Differential gene expression in ACTH -secreting and non-functioning pituitary tumors Eur. J. Endocrinol., December 1, 2007; 157(6): 717 - 724. [Abstract] [Full Text] [PDF]

				S. Vallette-Kasic, C. Couture, A. Balsalobre, Y. Gauthier, L. Metherell, M. Dattani, and J. Drouin The TPIT Gene Mutation M86R Associated with Isolated Adrenocorticotropin Deficiency Interferes with Protein: Protein Interactions J. Clin. Endocrinol. Metab., October 1, 2007; 92(10): 3991 - 3999. [Abstract] [Full Text] [PDF]

				S. Bilodeau, S. Vallette-Kasic, Y. Gauthier, D. Figarella-Branger, T. Brue, F. Berthelet, A. Lacroix, D. Batista, C. Stratakis, J. Hanson, et al. Role of Brg1 and HDAC2 in GR trans-repression of the pituitary POMC gene and misexpression in Cushing disease. Genes & Dev., October 15, 2006; 20(20): 2871 - 2886. [Abstract] [Full Text] [PDF]

				M Messager, C Carriere, X Bertagna, and Y de Keyzer RT-PCR analysis of corticotroph-associated genes expression in carcinoid tumours in the ectopic-ACTH syndrome Eur. J. Endocrinol., January 1, 2006; 154(1): 159 - 166. [Abstract] [Full Text] [PDF]

				S. Vallette-Kasic, T. Brue, A.-M. Pulichino, M. Gueydan, A. Barlier, M. David, M. Nicolino, G. Malpuech, P. Dechelotte, C. Deal, et al. Congenital Isolated Adrenocorticotropin Deficiency: An Underestimated Cause of Neonatal Death, Explained by TPIT Gene Mutations J. Clin. Endocrinol. Metab., March 1, 2005; 90(3): 1323 - 1331. [Abstract] [Full Text] [PDF]

				D. G. Morris, B. Kola, N. Borboli, G. A. Kaltsas, M. Gueorguiev, A. M. McNicol, R. Ferrier, T. H. Jones, S. Baldeweg, M. Powell, et al. Identification of Adrenocorticotropin Receptor Messenger Ribonucleic Acid in the Human Pituitary and Its Loss of Expression in Pituitary Adenomas J. Clin. Endocrinol. Metab., December 1, 2003; 88(12): 6080 - 6087. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Vallette-Kasic, S. Articles by Brue, T. Search for Related Content PubMed PubMed Citation Articles by Vallette-Kasic, S. Articles by Brue, T.