Early development of the thymus in Xenopus laevis. Issue 2 (5th December 2012)

• Record Type: Journal Article
• Authors: Lee, Young‐Hoon; Williams, Allison; Hong, Chang‐Soo; You, Youngjae; Senoo, Makoto; Saint‐Jeannet, Jean‐Pierre
• Is Part Of: Developmental dynamics. Volume 242:Issue 2(2013:Feb.)
• Page Start: 164
• Page End: 178
• Publication Date: 2012-12-05
• Subjects: Morphogenesis -- Periodicals; Anatomy -- Periodicals; Anatomie -- Périodiques; Biologie du développement -- Périodiques; 571.833
• DOI: 10.1002/dvdy.23905
• Languages: English
• ISSNs: 1058-8388

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p> <underline>Background:</underline> Although <italic>Xenopus laevis</italic> has been a model of choice for comparative and developmental studies of the immune system, little is known about organogenesis of the thymus, a primary lymphoid organ in vertebrates. Here we examined the expression of three transcription factors that have been functionally associated with pharyngeal gland development, <italic>gcm2, hoxa3</italic>, and <italic>foxn1</italic>, and evaluated the neural crest contribution to thymus development. <underline>Results:</underline> In most species <italic>Hoxa3</italic> is expressed in the third pharyngeal pouch endoderm where it directs thymus formation. In <italic>Xenopus</italic>, the thymus primordium is derived from the second pharyngeal pouch endoderm, which is <italic>hoxa3</italic>‐negative, suggesting that a different mechanism regulates thymus formation in frogs. Unlike other species <italic>foxn1</italic> is not detected in the epithelium of the pharyngeal pouch in <italic>Xenopus</italic>, rather, its expression is initiated as thymic epithelial cell starts to differentiate and express MHC class II molecules. Using transplantation experiments we show that while neural crest cells populate the thymus primordia, they are not required for the specification and initial development of this organ or for T‐cell differentiation in frogs. <underline>Conclusions:</underline> These studies provide novel information on early thymus development in <italic>Xenopus</italic>, and highlight a number of features that distinguish <italic>Xenopus</italic> from other organisms. Developmental Dynamics, 2012. © 2012 Wiley Periodicals, Inc.</p> </abstract>