Gene replacement reveals a specific role for E-cadherin in the formation of a functional trophectoderm

Abstract

During mammalian embryogenesis the trophectoderm represents the first epithelial structure formed. The cell adhesion molecule E-cadherin is ultimately necessary for the transition from compacted morula to the formation of the blastocyst to ensure correct establishment of adhesion junctions in the trophectoderm. Here, we analyzed to what extent E-cadherin confers unique adhesion and signaling properties in trophectoderm formation in vivo. Using a gene replacement approach, we introduced N-cadherin cDNA into the E-cadherin genomic locus. We show that the expression of N-cadherin driven from the E-cadherin locus reflects the expression pattern of endogenous E-cadherin. Heterozygous mice co-expressing E-and N-cadherin are vital and show normal embryonic development. Interestingly, N-cadherin homozygous mutant embryos phenocopy E-cadherin-null mutant embryos. Upon removal of the maternal E-cadherin, we demonstrate that N-cadherin is able to provide sufficient cellular adhesion to mediate morula compaction, but is insufficient for the subsequent formation of a fully polarized functional trophectoderm. When ES cells were isolated from N-cadherin homozygous mutant embryos and teratomas were produced, these ES cells differentiated into a large variety of tissue-like structures. Importantly, different epithelial-like structures expressing N-cadherin were formed, including respiratory epithelia, squamous epithelia with signs of keratinization and secretory epithelia with goblet cells. Thus, N-cadherin can maintain epithelia in differentiating ES cells, but not during the formation of the trophectoderm. Our results point to a specific and unique function for E-cadherin during mouse preimplantation development.

Timing and kinetics of E‐ to N‐cadherin switch during neurulation in the avian embryo

“…Consistent with this, biophysical studies demonstrated that E-cadherin mediates stronger bonds at the molecular level than any other cadherins (Dufour et al, 1999;Chu et al, 2006;Panorchan et al, 2006). Moreover, although E-cadherin and N-cadherin may transiently coexist in certain cells, they are generally mutually exclusive, and studies on epithelial cell lines or in mouse and Xenopus embryos in which E-and N-cadherins have been interchanged clearly indicate that they can only partially substitute each other (Luo et al, 2001;Kan et al, 2007;Wheelock et al, 2008;Nandadasa et al, 2009;Libusova et al, 2010).…”

A Cdh1HA knock‐in allele rescues the Cdh1−/− phenotype but shows essential Cdh1 function during placentation

“…) were unable to form a functional blastocyst, indicating a specific requirement for Cdh1 during trophectoderm formation that Cdh2 cannot supply (Kan et al, 2007).…”

“…Because the gene replacement of Cdh1 with Cdh2 resulted in a trophectoderm defect at E3.5 (Kan et al, 2007), we focused on the preimplantation development of embryos from heterozygous Cdh1 HA/þ intercrosses. In vivo and in vitro morulae of Cdh1 HA/HA embryos compact and form proper blastocysts similar to their littermates as shown by time-lapse recording (Supp.…”

“…A gene-targeting strategy was used as described (Stemmler et al, 2005;Kan et al, 2007). Briefly, a genomic fragment of the Cdh1 locus between À1.5 kb and þ11 kb was used to insert a cDNA coding for a C-terminally HAtagged version of Cdh1 combined with a pEGFP-N3-derived SV40 polyadenylation signal (Invitrogen) into the ATG codon.…”

“…Recently, we forced the expression of Cdh2 in the Cdh1 expression domain using a gene replacement approach. In Cdh1 Cdh2/þ mice, Cdh2 was co-expressed with Cdh1 in a correct spatio and temporal manner in addition to its endogenous expression (Stemmler et al, 2005;Kan et al, 2007). Homozygous mutant mice (Cdh1…”