title: The E3 ubiquitin ligase Hace1 is required for early embryonic development in Xenopus laevis.
abstract: BACKGROUND
  HECT domain and ankyrin repeat containing E3 ubiquitin protein ligase 1 (HACE1) regulates a wide variety of cellular processes. It has been shown that one of the targets of HACE1 is the GTP-bound form of the small GTPase Rac1. However, the role of HACE1 in early development remains unknown.
  
  
  RESULTS
  In situ hybridization revealed that Xenopus laevis hace1 is specifically expressed in the ectoderm at the blastula and gastrula stages and in the epidermis, branchial arch, kidney, and central nervous system at the tailbud stage. Knockdown of hace1 in Xenopus laevis embryos via antisense morpholino oligonucleotides led to defects in body axis elongation, pigment formation, and eye formation at the tadpole stage. Experiments with Keller sandwich explants showed that hace1 knockdown inhibited convergent extension, a morphogenetic movement known to be crucial for body axis elongation. In addition, time lapse imaging of whole embryos during the neurula stage indicated that hace1 knockdown also delayed neural tube closure. The defects caused by hace1 knockdown were partly rescued by knockdown of rac1. Moreover, embryos expressing a constitutively active form of Rac1 displayed phenotypes similar to those of embryos with hace1 knocked down.
  
  
  CONCLUSIONS
  Our results suggest that Xenopus laevis hace1 plays an important role in early embryonic development, possibly via regulation of Rac1 activity.
authors.affiliation: Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Iimura
authors.affiliation: Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
authors.forename: Fuhito
authors.initials: F
authors.lastname: Yamazaki
authors.affiliation: Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan. tsuzuki.m07@lif.kyoto-u.ac.jp.
authors.forename: Toshiyasu
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Endo
authors.affiliation: Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
authors.forename: Eisuke
authors.initials: E
authors.lastname: Nishida
authors.affiliation: Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
authors.forename: Morioh
authors.initials: M
authors.lastname: Kusakabe
keywords: Early development; HACE1; Xenopus laevis