Amphibian parathyroids: Morphological and functional aspects

Srivastav, Ajai K.; Das, Vijai Krishna; Das, Sanjib; Sasayama, Yuichi; Suzuki, Nobuo

doi:10.1002/jemt.1070320203

Cited by 8 publications

(7 citation statements)

References 60 publications

(130 reference statements)

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“…In Xenopus , we were not able to identify the parathyroid tissue and it has previously been noted to be inconspicuous and readily degenerates [36,46]. In chicken PTH expression was also detected in the pituitary gland and in Xenopus brain/pituitary extracts, which is in agreement with studies which showed that immunoactive protein was detected in pituitaries from sheep [47], and fish [3,48] (which lack an organized parathyroid gland structure).…”

Section: Discussionsupporting

confidence: 85%

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Gene structure, transcripts and calciotropic effects of the PTH family of peptides in Xenopus and chicken

et al. 2010

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BackgroundParathyroid hormone (PTH) and PTH-related peptide (PTHrP) belong to a family of endocrine factors that share a highly conserved N-terminal region (amino acids 1-34) and play key roles in calcium homeostasis, bone formation and skeletal development. Recently, PTH-like peptide (PTH-L) was identified in teleost fish raising questions about the evolution of these proteins. Although PTH and PTHrP have been intensively studied in mammals their function in other vertebrates is poorly documented. Amphibians and birds occupy unique phylogenetic positions, the former at the transition of aquatic to terrestrial life and the latter at the transition to homeothermy. Moreover, both organisms have characteristics indicative of a complex system in calcium regulation. This study investigated PTH family evolution in vertebrates with special emphasis on Xenopus and chicken.ResultsThe PTH-L gene is present throughout the vertebrates with the exception of placental mammals. Gene structure of PTH and PTH-L seems to be conserved in vertebrates while PTHrP gene structure is divergent and has acquired new exons and alternative promoters. Splice variants of PTHrP and PTH-L are common in Xenopus and chicken and transcripts of the former have a widespread tissue distribution, although PTH-L is more restricted. PTH is widely expressed in fish tissue but from Xenopus to mammals becomes largely restricted to the parathyroid gland. The N-terminal (1-34) region of PTH, PTHrP and PTH-L in Xenopus and chicken share high sequence conservation and the capacity to modify calcium fluxes across epithelia suggesting a conserved role in calcium metabolism possibly via similar receptors.ConclusionsThe parathyroid hormone family contains 3 principal members, PTH, PTHrP and the recently identified PTH-L. In teleosts there are 5 genes which encode PTHrP (2), PTH (2) and PTH-L and in tetrapods there are 3 genes (PTHrP, PTH and PTH-L), the exception is placental mammals which have 2 genes and lack PTH-L. It is hypothesized that genes of the PTH family appeared at approximately the same time during the vertebrate radiation and evolved via gene duplication/deletion events. PTH-L was lost from the genome of eutherian mammals and PTH, which has a paracrine distribution in lower vertebrates, became the product of a specific endocrine tissue in Amphibia, the parathyroid gland. The PTHrP gene organisation diverged and became more complex in vertebrates and retained its widespread tissue distribution which is congruent with its paracrine nature.

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Section: Discussionsupporting

confidence: 85%

“…Xenopus PTH was expressed in bone, kidney, lung and nervous tissue (mixed brain and pituitary). The presence of PTH family members was not established in the amphibian parathyroid gland as its small size and variable morphology made it difficult to collect [36]. …”

Section: Resultsmentioning

confidence: 99%

Gene structure, transcripts and calciotropic effects of the PTH family of peptides in Xenopus and chicken

et al. 2010

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“…In tetrapods, calcium regulation is largely dependent on the interaction between parathyroid gland, which produces PTH, vitamin D, and cellular bone, which acts as a calcium reservoir. In contrast with fish, amphibians have functional parathyroid glands (32) and PTH receptors (33) and a vitamin D receptor (34) has recently been cloned from Xenopus . These hormone receptors, involved in calcium homeostasis, are highly homologous to those found in mammals, indicating that amphibians evolved mechanisms for controlling calcium homeostasis very similar to those found in mammals, including establishing bone as a readily available calcium reservoir.…”

Section: Discussionmentioning

confidence: 99%

Matrix Gla Protein in Xenopus laevis: Molecular Cloning, Tissue Distribution, and Evolutionary Considerations

Cancela

Ohresser

Reia

et al. 2001

Journal of Bone and Mineral Research

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Matrix Gla protein (MGP) belongs to the family of vitamin K-dependent, Gla-containing proteins and in higher vertebrates, is found in the extracellular matrix of mineralized tissues and soft tissues. MGP synthesis is highly regulated at the transcription and posttranscription levels and is now known to be involved in the regulation of extracellular matrix calcification and maintenance of cartilage and soft tissue integrity during growth and development. However, its mode of action at the molecular level remains unknown. Because there is a large degree of conservation between amino acid sequences of shark and human MGP, the function of MGP probably has been conserved throughout evolution. Given the complexity of the mammalian system, the study of MGP in a lower vertebrate might be advantageous to relate the onset of MGP expression with specific events during development. Toward this goal, MGP was purified from Xenopus long bones and its N-terminal amino acid sequence was determined and used to clone the Xenopus MGP complementary DNA (cDNA) by a mixture of reverse-transcription (RT)-and 5-rapid amplification of cDNA ends (RACE)-polymerase chain reaction (PCR). MGP messenger RNA (mRNA) was present in all tissues analyzed although predominantly expressed in Xenopus bone and heart and its presence was detected early in development at the onset of chondrocranium development and long before the appearance of the first calcified structures and metamorphosis. These results show that in this system, as in mammals, MGP may be required to delay or prevent mineralization of cartilage and soft tissues during the early stages of development and indicate that Xenopus is an adequate model organism to further study MGP function during growth and development. (J Bone Miner Res 2001;16:1611-1621)

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“…3). The origin of parenchymal cells of this gland is common to that of the epithelial cell of the gill (see, Srivastav et al, 1995a). Why do parathyroid glands differentiate from the branchial epithelium?…”

Section: Various Circumstances In Vertebrates Other Than Fishesmentioning

confidence: 99%

Amphibian parathyroids: Morphological and functional aspects

Cited by 8 publications

References 60 publications

Gene structure, transcripts and calciotropic effects of the PTH family of peptides in Xenopus and chicken

Gene structure, transcripts and calciotropic effects of the PTH family of peptides in Xenopus and chicken

Matrix Gla Protein in Xenopus laevis: Molecular Cloning, Tissue Distribution, and Evolutionary Considerations

Hormonal Control of Ca Homeostasis in Lower Vertebrates: Considering the Evolution

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