N‐cadherin transcripts in Xenopus laevis from early tailbud to tadpole

Abstract

Cadherins are Ca+ +-dependent cell adhesion molecules which play a key role in morphogenesis and histogenesis. T w o mRNAs clones (8 and 9) corresponding to two N-cadherin pseudo-allelic genes are present in Xenopus Zaeuis. We report here that these transcripts share a highly homologous coding region but diverge in the non-coding region. We have determined the pattern of N-cadherin expression at the mRNA level by in situ hybridization with a riboprobe complementary to the EC5 domain of Xenopus Ncadherin clone 8. This part of the sequence is the least conserved in the cadherin gene family, minimizing the risk of cross-hybridization to other cadherins. N-cadherin transcripts are not detectable in the first stages of development. Expression first appears in the neural plate and reaches its maximum level in the CNS at tailbud stage. From early tadpole, it diminishes, so that a very weak signal is detected in the premetamorphic frog brain. N-cadherin expression is not uniform within the CNS, with some areas such as the roof of the rhombencephalon and the olfactory bulbs expressing higher levels of the transcripts. N-cadherin is present in several mesodermal derivatives such as the notochord, the pronephros, and the heart. It is, however, virtually absent from the myotomes and appears in skeletal muscles at later stages of differentiation. All placodes express high levels of N-cadherin. The non-neural ectoderm and the endoderm are always negative. In the brain and the heart, high levels of hybridization are observed with probes corresponding to both copies of the N-cadherin pseudo-allelic genes in their 5' non-coding region, indicating that both alleles are transcribed. o 1992 Wiley-Liss, Inc.

Identification of XLerk, an Eph family ligand regulated during mesoderm induction and neurogenesis in Xenopus laevis

“…Concurrent with motor neuron innervations to the somites (at stage 22), in which motor axons invade the myotomes, the expression of focal adhesion molecules including Fak, tanabin, talin, paxillin and integrins may also regulate somite formation (Hens and DeSimone, 1995;Hemmati-Brivanlou et al, 1992;Krotoski and Bronner-Fraser, 1990;Lefcort et al, 1992;Ransom et al, 1993;Tomaselli and Reichardt, 1989). In addition, both N-Cadherin, a neural cell adhesion molecule, and XLerk are expressed in the olfactory placode, hindbrain, otic vesicle and heart anlage (Simonneau et al, 1992).…”

Glycobiology of the Olfactory System

“…Whereas the distribution of E-cadherin varies in accordance with changes in olfactory axon development [Whitesides and LaMantia, 1996], N-cadherin is expressed throughout the entire olfactory nerve in human fetuses suggesting that the growth of olfactory axons to their target may be mediated by these adhesion molecules [Simonneau et al, 1992;Norgren and Brackenbury, 1993]. PB-cadherin is responsible for Ca 2+ -dependent cell adhesion.…”

Xenopus cadherins: Sorting out types and functions in embryogenesis

“…The expression of N-cadherin is turned on with neural induction in the presumptive neural ectoderm (Detrick et al, 1990;Simonneau et al, 1992). In the neural plate, the expression of E-cadherin vanishes at the same time.…”

“…"Data are from the following sources: EP/C-cadherin, Choi and Gumbiner (1989) and Ginsberg et al (1991); XB/U-cadherin, Herzberg et al (1991) and Angres et al (1991); XmN-cadherin, Tashiro et al (1995); E-cadherid XTCAD-1, Choi et al (1991) and Tooi et al (1994); N-cadherin, Simonneau et al (1992); F-cadherin: Espeseth et al (1995). bn.d., Not determined.…”

“…Sequence differences up to 4% are defined as allelic variations, e.g., the two N-cadherin sequences (Detrick et al, 1990;Ginsberg et al, 1991;Simonneau et al, 1992), E-cadherin and XTCAD-1 (our own comparison), or EP-and C-cadherin (Levine et al, 1994). A sequence divergence of about 8-10% between two Xenopus laevis genes, e.g., XB/U and EP/C-cadherin, characterizes them as pseudoalleles based on the tetraploidy of the genome.…”