NCBI Summary:
This gene encodes a member of the RIEG/PITX homeobox family, which is in the bicoid class of homeodomain proteins. The encoded protein acts as a transcription factor and regulates procollagen lysyl hydroxylase gene expression. This protein plays a role in the terminal differentiation of somatotroph and lactotroph cell phenotypes, is involved in the development of the eye, tooth and abdominal organs, and acts as a transcriptional regulator involved in basal and hormone-regulated activity of prolactin. Mutations in this gene are associated with Axenfeld-Rieger syndrome, iridogoniodysgenesis syndrome, and sporadic cases of Peters anomaly. A similar protein in other vertebrates is involved in the determination of left-right asymmetry during development. Alternatively spliced transcript variants encoding distinct isoforms have been described. [provided by RefSeq]
General function
Nucleic acid binding, DNA binding, Transcription factor
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Cellular localization
Nuclear
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Ovarian function
Germ cell development
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PITX2 controls asymmetric gonadal development in both sexes of the chick and can rescue the degeneration of the right ovary. Guioli S et al. The gonads arise on the ventromedial surface of each mesonephros. In most birds, female gonadal development is unusual in that only the left ovary becomes functional, whereas that on the right degenerates during embryogenesis. Males develop a pair of equally functional testes. We show that the chick gonads already have distinct morphological and molecular left-right (L-R) characteristics in both sexes at indifferent (genital ridge) stages and that these persist, becoming more elaborate during sex determination and differentiation, but have no consequences for testis differentiation. We find that these L-R differences depend on the L-R asymmetry pathway that controls the situs of organs such as the heart and gut. Moreover, a key determinant of this, Pitx2, is expressed asymmetrically, such that it is found only in the left gonad in both sexes from the start of their development. Misexpression of Pitx2 on the right side before and during gonadogenesis is sufficient to transform the right gonad into a left-like gonad. In ZW embryos, this transformation rescues the degenerative fate of the right ovary, allowing for the differentiation of left-like cortex containing meiotic germ cells. There is therefore a mechanism in females that actively promotes the underlying L-R asymmetry initiated by Pitx2 and the degeneration of the right gonad, and a mechanism in males that allows it to be ignored or overridden.
Pitx2 regulates gonad morphogenesis. Rodr?ez-Le? et al. Organ shape and size, and, ultimately, organ function, relate in part to the cell and tissue spatial arrangement that takes place during embryonic development. Despite great advances in the genetic regulatory networks responsible for tissue and organ development, it is not yet clearly understood how specific gene functions are linked to the specific morphogenetic processes underlying the internal organ asymmetries found in vertebrate animals. During female chick embryogenesis, and in contrast to males where both testes develop symmetrically, asymmetrical gonad morphogenesis results in only one functional ovary. The disposition of paired organs along the left-right body axis has been shown to be regulated by the activity of the homeobox containing gene pitx2. We have found that pitx2 regulates cell adhesion, affinity, and cell recognition events in the developing gonad primordium epithelia. This in turn not only allows for proper somatic development of the gonad cortex but also permits the proliferation and differentiation of primordial germ cells. We illustrate how Pitx2 activity directs asymmetrical gonad morphogenesis by controlling mitotic spindle orientation of the developing gonad cortex and how, by modulating cyclinD1 expression during asymmetric ovarian development, Pitx2 appears to control gonad organ size. All together our observations indicate that the effects elicited by Pitx2 during the development of the female chick ovary are critical for cell topology, growth, fate, and ultimately organ morphogenesis and function.
Expression regulated by
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Ovarian localization
Primordial Germ Cell, Oocyte, Granulosa, Theca
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Expression of PITX2 Homeodomain Transcription Factor during Rat Gonadal Development in a Sexually Dimorphic Manner. Nandi SS et al. PITX2, a multifunctional Paired-like homeodomain transcription factor, plays obligatory role during development of organs like heart, brain and pituitary. It regulates differentiation of vascular smooth muscle cells and hematopoietic stem cells. Although we earlier reported the Pitx2/PITX2 expression in gonad, but the expression pattern of its different isoforms in mammalian gonads especially during development is still not known. As PITX2 participates in the development of multiple organs and different homeobox genes have been shown to control gonadal functions, we wanted to investigate the role of PITX2 in gonadal development and its function. The objective of our study was to know the expression profile of different Pitx2/PITX2 isoforms and its localization throughout the development of gonads. Here we show the temporal and spatial expression pattern of Pitx2/PITX2 and its localization throughout the embryonic and postnatal stages of rat gonads. Pitx2/PITX2 expression profile reveals the differential and dimorphic expression pattern of its two isoforms PITX2B2 and-C throughout the embryonic development stages and also in the postnatal stages, where it becomes more prominent. This is the first report where PITX2 homeodomain transcription factor shows isoform-specific sexually dimorphic expression. In addition, PITX2 localization was found in the embryonic ovarian primordial germ cell clusters and germ cells inside the testicular cords and also in somatic cells. In adults, ovarian granulosa and theca cells as well as germ cells inside the seminiferous tubules in testis express PITX2. All the evidences suggest that the differential expression of PITX2 might be associated with sex-specific embryonic and postnatal gonadal development and the physiological processes.
Distinguishing direct from indirect roles for bicoid mRNA localization factors. Weil TT et al. Localization of bicoid mRNA to the anterior of the Drosophila oocyte is essential for patterning the anteroposterior body axis in the early embryo. bicoid mRNA localizes in a complex multistep process involving transacting factors, molecular motors and cytoskeletal components that remodel extensively during the lifetime of the mRNA. Genetic requirements for several localization factors, including Swallow and Staufen, are well established, but the precise roles of these factors and their relationship to bicoid mRNA transport particles remains unresolved. Here we use live cell imaging, super-resolution microscopy in fixed cells and immunoelectron microscopy on ultrathin frozen sections to study the distribution of Swallow, Staufen, actin and dynein relative to bicoid mRNA during late oogenesis. We show that Swallow and bicoid mRNA are transported independently and are not colocalized at their final destination. Furthermore, Swallow is not required for bicoid transport. Instead, Swallow localizes to the oocyte plasma membrane, in close proximity to actin filaments, and we present evidence that Swallow functions during the late phase of bicoid localization by regulating the actin cytoskeleton. In contrast, Staufen, dynein and bicoid mRNA form nonmembranous, electron dense particles at the oocyte anterior. Our results exclude a role for Swallow in linking bicoid mRNA to the dynein motor. Instead we propose a model for bicoid mRNA localization in which Swallow is transported independently by dynein and contributes indirectly to bicoid mRNA localization by organizing the cytoskeleton, whereas Staufen plays a direct role in dynein-dependent bicoid mRNA transport.