Expression and evolution of the Tiki1 and Tiki2 genes in vertebrates
Developmental Expression Pattern | Published: 1 October 2014
Alice H. Reis#,1, Bryan T. Macdonald#,2, Kerstin Feistel3, Jose M. Brito1, Nathalia G. Amado1, Chiwei Xu2, Jose G. Abreu*,1 and Xi He*,2
1Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, 2F. M. Kirby Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA and 3Institute of Zoology, University of Hohenheim, Stuttgart, Germany
Tiki1 is a Wnt protease and antagonist specifically expressed in the Spemann-Mangold Organizer and is required for head formation in Xenopus embryos. Here we report neighbor-joining phylogenetic analysis of vertebrate Tiki genes and their mRNA expression patterns in chick, mouse, and rabbit embryos. Tiki1 and Tiki2 orthologues are highly conserved, and exhibit similar but also different developmental expression patterns among the vertebrate/mammalian species analyzed. The Tiki1 gene is noticeably absent in the rodent lineage, but is present in lagomorphs and all other vertebrate/mammalian species examined. Expression in Hensen's node, the equivalent of the Xenopus Organizer, was observed for Chick Tiki2 and Rabbit Tiki1 and Tiki2. Mouse Tiki2 was detected at low levels at gastrulation and head fold stages, but not in the node. Mouse Tiki2 and chick Tiki1 display similar expression in the dorsal spinal cord. Chick Tiki1 expression was also detected in the surface ectoderm and maxillary bud, while chick Tiki2 was found in the anterior intestinal portal, head mesenchyme and primitive atrium. Our expression analyses provide evidence that Tiki1 and Tiki2 are evolutionarily conserved among vertebrate species and their expression in the Organizer and other regions suggests contributions of these Wnt inhibitors to embryonic patterning, as well as organogenesis. Our analyses further reveal mis-regulation of TIKI1 and TIKI2 in human cancer and diseases.
Tiki1, Tiki2, Wnt, organizer, head induction, organogenesis