13‐cis‐retinoic acid alters neural crest cells expressing Krox‐20 and Pax‐2 in macaque embryos

• Published in: The Anatomical record 1999-06, Vol.255 (2), p.142-154
• Main Authors: Makori, Norbert, Peterson, Pamela E., Wei, Xin, Hummler, Hans, Hendrickx, Andrew G.
• Format: Article
• Language: English
• Subjects: Animals; Branchial Region - drug effects; Branchial Region - embryology; Branchial Region - metabolism; Cochlea - drug effects; Cochlea - embryology; Cochlea - metabolism; craniofacial; DNA-Binding Proteins - metabolism; Early Growth Response Protein 2; Embryonic and Fetal Development - drug effects; Female; hindbrain; Image Processing, Computer-Assisted; Immunoenzyme Techniques; Isotretinoin - toxicity; Krox-20 protein; Macaca fascicularis; Macaca mulatta; macaque embryo; neural crest; Neural Crest - drug effects; Neural Crest - embryology; Pax-2 protein; PAX2 Transcription Factor; Pregnancy; retinoid embryopathy; Rhombencephalon - drug effects; Rhombencephalon - embryology; Rhombencephalon - metabolism; Teratogens - toxicity; Transcription Factors - metabolism
• ISSN: 0003-276X; 1097-0185
• DOI: 10.1002/(SICI)1097-0185(19990601)255:2<142::AID-AR4>3.0.CO;2-D

This study investigates hindbrain and associated neural crest (NCC), otocyst, and pharyngeal arch development in monkey embryos following teratogenic exposure to 13‐cis‐retinoic acid (cRA). cRA was orally administered (5 mg/kg) to pregnant long‐tailed macaques (Macaca fascicularis) between gestational days (GD) 12 and 27. Embryos were surgically collected at desired stages during treatment, analyzed for external morphological changes, and processed for immunohistochemistry. Two transiently expressed nuclear proteins, Krox‐20 and Pax‐2, were used as markers for the target cellular and anatomical structures. Rhombomere (r) expression patterns of Pax‐2 (r4/r6) and Krox‐20 (r3/r5) were maintained after cRA treatment, but r4 and r5 were substantially reduced in size. In untreated embryos, Krox‐20 immunoreactive NCC derived from r5 migrated caudally around the developing otocyst to contribute to the third pharyngeal arch mesenchyme. In cRA‐treated embryos, a subpopulation of NCC rostral to the otocyst also showed Krox‐20 immunoreactivity, but there was a substantial reduction in Krox‐20 post‐otic NCC. Pax‐2 immunoreactive NCC migrating from r4 to the second pharyngeal arch were substantially reduced in numbers in treated embryos. Alteration in the otic anlage included delayed invagination, abnormal relationship with the adjacent hindbrain epithelium, and altered expression boundaries for Pax‐2. cRA‐associated changes in the pharyngeal arch region due to cRA included truncation of the distal portion of the first arch and reduction in the size of the second arch. These alterations in hindbrain, neural crest, otic anlage, and pharyngeal arch morphogenesis could contribute to some of the craniofacial malformations in the macaque fetus associated with exposure to cRA. Anat Rec 255:142–154, 1999. © 1999 Wiley‐Liss, Inc.