Reduced expression of the LIM-homeobox gene Lhx3 impairs growth and differentiation of Rathke’s pouch and increases cell apoptosis during mouse pituitary development

Analysis of an allelic series in mice revealed that the Pitx2 homeobox gene is required at multiple stages of pituitary development. It is necessary for initiating expansion of Rathke’s pouch and maintaining expression of the fetal-specific transcription factors Hesx1 and Prop1. At later stages Pitx2 is necessary for specification and expansion of the gonadotropes and Pit1 lineage within the ventral and caudomedial anterior pituitary. Mechanistically, this is due to the dependence of several critical lineage-specific transcription factors, Pit1, Gata2, Egr1 and Sf1, on a threshold level of PITX2. The related Pitx1 gene has a role in hormone gene transcription, and it is important late in ontogeny for the final expansion of the differentiated cell types. Pitx1 and Pitx2 have overlapping functions in the expansion of Rathke’s pouch, revealing the sensitivity of pituitary organogenesis to the dosage of the PITX family. The model developed for PITX gene function in pituitary development provides a better understanding of the etiology of Rieger syndrome and may extend to other PITX-sensitive developmental processes.

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Memoirs: The Development of the Pituitary of the Laboratory Mouse

Journal of Cell Science ◽

10.1242/jcs.s2-87.345.3 ◽

1946 ◽

Vol s2-87 (345) ◽

pp. 3-29

Author(s):

T. KERR

Keyword(s):

Mitotic Activity ◽

Blood Supply ◽

Laboratory Mouse ◽

Differential Growth ◽

Internal Factors ◽

Rathke’S Pouch ◽

Rathke's Pouch ◽

Mouse Pituitary

1. A description is given of the development of the mouse pituitary, with particular reference to some obscure points in the general embryology of the mammalian gland. 2. The establishment of the neuro-ectodermal union of brain floor and stomodaeal roof precedes the appearance of Rathke's pouch; its importance and the effects of external and internal factors on pouch formation and closure are discussed. It is considered that the process cannot be entirely due to mechanical influences and differential growth. 3. The nervous lobe forms from a groove in the premammillary lamina which deepens and separates off. Later enlargement of the lobe is due to the reorganization of its cells, the appearance of fibres and a low but steady mitotic activity. 4. The establishment of the lateral lobes and the blood supply, the distribution of mitoses, the development of processes from the proximal into the nervous lobe and other points are recorded. I am again in debt to Professor E. A. Spaul, D.Sc., for reading the manuscript and for his invaluable discussion of the interpretations involved.

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A novel inducible element, activated by contact with Rathke’s pouch, is present in the regulatory region of the Rpx/Hesx1 homeobox gene

Developmental Biology ◽

10.1016/s0012-1606(03)00218-5 ◽

2003 ◽

Vol 260 (1) ◽

pp. 68-78 ◽

Cited By ~ 20

Author(s):

Edit Hermesz ◽

Lisa Williams-Simons ◽

Kathleen A. Mahon

Keyword(s):

Regulatory Region ◽

Homeobox Gene ◽

Rathke’S Pouch ◽

Rathke's Pouch

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SAT-291 SIX3 Is Essential for Hypothalamic and Pituitary Development

Journal of the Endocrine Society ◽

10.1210/jendso/bvaa046.159 ◽

2020 ◽

Vol 4 (Supplement_1) ◽

Author(s):

Hironori Bando ◽

Michelle L Brinkmeier ◽

Frederic Castinetti ◽

Peter Gergics ◽

Amanda H Mortensen ◽

...

Keyword(s):

Bmp Signaling ◽

Pituitary Hormone ◽

Homeodomain Protein ◽

Loss Of Function ◽

Shh Signaling ◽

Rathke’S Pouch ◽

Pituitary Development ◽

Rathke's Pouch ◽

Oral Ectoderm ◽

Congenital Hypopituitarism

Abstract The genetic basis for congenital hypopituitarism and related disorders is beginning to emerge, and over causal 30 genes have been identified, including six in the SHH signaling pathway. Mutations in some of these genes can also cause holoprosencephaly (HPE) or septo-optic dysplasia. SIX3 is a homeodomain protein expressed in the developing brain, pituitary gland, and eye. It activates SHH signaling and represses BMP signaling. Heterozygous mutations in SIX3 cause variable HPE in humans and mice. We identified a rare, heterozygous variant in SIX3 in two children with neonatal GH and TSH deficiency and stalk interruption, p.P74R. Using transient transfection in 3T3 cells, we demonstrated that the variant reduced the ability of SIX3 to transactivate the SHH enhancer and promoter of FOXG1, suggesting that the variant could be deleterious. To understand the role of SIX3 in hypothalamic and pituitary development we used Nkx2.1-cre and Prop1-cre to delete Six3 in mice. The Nkx2.1-cre, Six3flox/flox embryos had no evidence of infundibulum evagination or expression of Fgf10 or Tcf7l2 at e11.5. The oral ectoderm invaginated in mutants, but no definitive Rathke’s pouch formed. There was no evidence of Lhx3 expression and only trace amounts of Pitx1, indicating that pituitary induction failed due to the lack of Six3 in the developing hypothalamus. Similarly, disruption of Six3 expression in Rathke’s pouch using Prop1-cre ablated pituitary development. Together, these data reveal essential roles of Six3 in both the neural and oral ectoderm for hypothalamic and pituitary development, respectively. Heterozygous loss of function variants in SIX3 could be a contributor to multiple pituitary hormone deficiencies in children, especially if there are associated craniofacial abnormalities.

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Hedgehog signaling is required for pituitary gland development

Development ◽

10.1242/dev.128.3.377 ◽

2001 ◽

Vol 128 (3) ◽

pp. 377-386 ◽

Cited By ~ 8

Author(s):

M. Treier ◽

S. O'Connell ◽

A. Gleiberman ◽

J. Price ◽

D.P. Szeto ◽

...

Keyword(s):

Pituitary Gland ◽

Hedgehog Signaling ◽

Homeobox Gene ◽

Cell Types ◽

Oral Epithelium ◽

Regulatory Sequences ◽

Rathke’S Pouch ◽

Rathke's Pouch ◽

Oral Ectoderm ◽

Gland Development

Pituitary gland development serves as an excellent model system in which to study the emergence of distinct cell types from a common primordium in mammalian organogenesis. We have investigated the role of the morphogen Sonic hedgehog (SHH) in outgrowth and differentiation of the pituitary gland using loss- and gain-of-function studies in transgenic mice. Shh is expressed throughout the ventral diencephalon and the oral ectoderm, but its expression is subsequently absent from the nascent Rathke's pouch as soon as it becomes morphologically visible, creating a Shh boundary within the oral epithelium. We used oral ectoderm/Rathke's pouch-specific 5′ regulatory sequences (Pitx1(HS)) from the bicoid related pituitary homeobox gene (Pitx1) to target overexpression of the Hedgehog inhibitor Hip (Huntingtin interacting protein) to block Hedgehog signaling, finding that SHH is required for proliferation of the pituitary gland. In addition, we provide evidence that Hedgehog signaling, acting at the Shh boundary within the oral ectoderm, may exert a role in differentiation of ventral cell types (gonadotropes and thyrotropes) by inducing Bmp2 expression in Rathke's pouch, which subsequently regulates expression of ventral transcription factors, particularly Gata2. Furthermore, our data suggest that Hedgehog signaling, together with FGF8/10 signaling, synergizes to regulate expression of the LIM homeobox gene Lhx3, which has been proved to be essential for initial pituitary gland formation. Thus, SHH appears to exert effects on both proliferation and cell-type determination in pituitary gland development.

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Formation of Rathke's pouch requires dual induction from the diencephalon

Development ◽

10.1242/dev.125.23.4835 ◽

1998 ◽

Vol 125 (23) ◽

pp. 4835-4840 ◽

Cited By ~ 11

Author(s):

N. Takuma ◽

H.Z. Sheng ◽

Y. Furuta ◽

J.M. Ward ◽

K. Sharma ◽

...

Keyword(s):

Regulatory Gene ◽

Molecular Genetic ◽

Homeobox Gene ◽

Subsequent Development ◽

Null Mutant ◽

Rathke’S Pouch ◽

Rathke's Pouch ◽

Bmp4 Expression ◽

Molecular Genetic Evidence

Targeted disruption of the homeobox gene T/ebp (Nkx2.1, Ttf1, Titf1) in mice results in ablation of the pituitary. Paradoxically, while T/ebp is expressed in the ventral diencephalon during forebrain formation, it is not expressed in Rathke's pouch or in the pituitary gland at any time of embryogenesis. Examination of pituitary development in the T/ebp homozygous null mutant embryos revealed that a pouch rudiment is initially formed but is eliminated by programmed cell death before formation of a definitive pouch. In the diencephalon of the mutant, Bmp4 expression is maintained, whereas Fgf8 expression is not detectable. These data and additional genetic and molecular observations suggest that Rathke's pouch develops in a two-step process that requires at least two sequential inductive signals from the diencephalon. First, BMP4 is required for induction and formation of the pouch rudiment, a role confirmed by analysis of Bmp4 homozygous null mutant embryos. Second, FGF8 is necessary for activation of the key regulatory gene Lhx3 and subsequent development of the pouch rudiment into a definitive pouch. This study provides firm molecular genetic evidence that morphogenesis of the pituitary primordium is induced in vivo by signals from the adjacent diencephalon.

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Rpx: a novel anterior-restricted homeobox gene progressively activated in the prechordal plate, anterior neural plate and Rathke's pouch of the mouse embryo

Development ◽

10.1242/dev.122.1.41 ◽

1996 ◽

Vol 122 (1) ◽

pp. 41-52 ◽

Cited By ~ 23

Author(s):

E. Hermesz ◽

S. Mackem ◽

K.A. Mahon

Keyword(s):

Homeobox Gene ◽

Cell Types ◽

Early Embryo ◽

Neural Plate ◽

Specific Cell ◽

Expression Domain ◽

Rathke’S Pouch ◽

Rathke's Pouch ◽

Prechordal Plate ◽

Early Expression

We have isolated a new murine homeobox gene, Rpx (for Rathke's pouch homeobox), that is dynamically expressed in the prospective cephalic region of the embryo during gastrulation. Early expression is seen in the anterior midline endoderm and prechordal plate precursor. Expression is subsequently activated in the overlying ectoderm of the cephalic neural plate, suggesting that inductive contact with Rpx-expressing mesendoderm is required for this expression. Subsequently, Rpx expression is extinguished in the mesendoderm while remaining in the prospective prosencephalic region of the neural plate ectoderm. Ultimately, transcripts become restricted to Rathke's pouch, the primordium of the pituitary, which is known to be derived from the most anterior ectoderm of the early embryo. Down regulation of Rpx in the pouch coincides with the differentiation of pituitary-specific cell types. Rpx is the earliest known marker for the pituitary primordium, suggestive of a role in the early determination or differentiation of the pituitary. Since Rpx is expressed so dynamically and so early in the anterior region of the embryo, and since its early expression domain is much more extensive than the region fated to form the pituitary, it is likely that Rpx is involved in the initial determination of the anterior (prechordal) region of the embryo.

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The Genetic Backdrop of Hypogonadotropic Hypogonadism

International Journal of Molecular Sciences ◽

10.3390/ijms222413241 ◽

2021 ◽

Vol 22 (24) ◽

pp. 13241

Author(s):

Anna Szeliga ◽

Michal Kunicki ◽

Marzena Maciejewska-Jeske ◽

Natalia Rzewuska ◽

Anna Kostrzak ◽

...

Keyword(s):

Developmental Disorders ◽

Hypogonadotropic Hypogonadism ◽

Reproductive Function ◽

Primary Amenorrhea ◽

Posterior Lobe ◽

Cyclic Activity ◽

Subsequent Formation ◽

Rathke’S Pouch ◽

Pituitary Development ◽

Rathke's Pouch

The pituitary is an organ of dual provenance: the anterior lobe is epithelial in origin, whereas the posterior lobe derives from the neural ectoderm. The pituitary gland is a pivotal element of the axis regulating reproductive function in mammals. It collects signals from the hypothalamus, and by secreting gonadotropins (FSH and LH) it stimulates the ovary into cyclic activity resulting in a menstrual cycle and in ovulation. Pituitary organogenesis is comprised of three main stages controlled by different signaling molecules: first, the initiation of pituitary organogenesis and subsequent formation of Rathke’s pouch; second, the migration of Rathke’s pouch cells and their proliferation; and third, lineage determination and cellular differentiation. Any disruption of this sequence, e.g., gene mutation, can lead to numerous developmental disorders. Gene mutations contributing to disordered pituitary development can themselves be classified: mutations affecting transcriptional determinants of pituitary development, mutations related to gonadotropin deficiency, mutations concerning the beta subunit of FSH and LH, and mutations in the DAX-1 gene as a cause of adrenal hypoplasia and disturbed responsiveness of the pituitary to GnRH. All these mutations lead to disruption in the hypothalamic–pituitary–ovarian axis and contribute to the development of primary amenorrhea.

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SIX3 Variant Causes Pituitary Stalk Interruption Syndrome and Combined Pituitary Hormone Deficiency

Journal of the Endocrine Society ◽

10.1210/jendso/bvab048.1079 ◽

2021 ◽

Vol 5 (Supplement_1) ◽

pp. A530-A530

Author(s):

Hironori Bando ◽

Michelle Brinkmeier ◽

Peter Gergics ◽

Qing Fang ◽

Amanda Helen Mortensen ◽

...

Keyword(s):

Pituitary Gland ◽

Genetic Interaction ◽

Pituitary Stalk ◽

Hormone Deficiency ◽

Pituitary Hormone ◽

Beta Catenin ◽

Loss Of Function ◽

Rathke’S Pouch ◽

Pituitary Development ◽

Rathke's Pouch

Abstract The genetic basis for congenital hypopituitarism and related disorders is beginning to emerge, and over 30 causal genes have been identified. Mutations in some of these genes can also cause holoprosencephaly (HPE) or septo-optic dysplasia. SIX3 is a homeodomain protein expressed in the developing brain, pituitary gland, and eye. Heterozygous mutations in SIX3 cause variable HPE in humans and mice. We identified two children with neonatal GH and TSH deficiency and stalk interruption who were doubly heterozygous for rare, likely deleterious variants in SIX3 and POU1F1. Functional studies demonstrated that both variants are disruptive. We used Six3 and Pou1f1 loss of function mice to assess the genetic interaction between Six3 and Pou1f1. Six3 heterozygotes have variable pituitary gland dysmorphology, while Pou1f1 heterozygotes are normal. A significant portion of the Six3+/-; Pou1f1+/dw doubly heterozygous mice have a more pronounced pituitary phenotype than Six3+/-, supporting the possibility of digenic pituitary disease. To understand the role of SIX3 in pituitary and hypothalamic development, we used Prop1-cre and Nkx2.1-cre to delete Six3. Disruption of Six3 expression in Rathke’s pouch caused poor activation of Lhx3 expression and arrested anterior pituitary development. The Nkx2.1-cre, Six3flox/flox embryos had no evidence of infundibulum evagination and failed to induce FGF and BMP signaling, which normally drive expansion of Rathke’s pouch. By E11.5 cells in Rathke’s pouch underwent apoptosis. The Nkx2.1-cre, Six3flox/flox embryos failed to activate expression of Lhx2 and Tbx3 in the neural ectoderm. These embryos had elevated CCND1, MYCN, and Axin2 expression in the area of the presumptive infundibulum. This indicates that SIX3 is necessary to repress cell proliferation and Wnt/beta-catenin signals to promote formation of the pituitary stalk. Thus, Six3 has essential roles in both the neural and oral ectoderm for hypothalamic and pituitary development, respectively. Heterozygous loss of function variants in SIX3 could be a contributor to multiple pituitary hormone deficiencies in children, especially if there are associated craniofacial abnormalities or PSIS.

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