Simonneau L et al. (1992), N-cadherin transcripts in Xenopus laevis from e...

XB-ART-23540

Dev Dyn 1992 Aug 01;1944:247-60. doi: 10.1002/aja.1001940402.

Show Gene links Show Anatomy links

N-cadherin transcripts in Xenopus laevis from early tailbud to tadpole.

Simonneau L , Broders F , Thiery JP .

???displayArticle.abstract???
Cadherins are Ca(++)-dependent cell adhesion molecules which play a key role in morphogenesis and histogenesis. Two mRNAs clones (8 and 9) corresponding to two N-cadherin pseudo-allelic genes are present in Xenopus laevis. 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 N-cadherin 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.

???displayArticle.pubmedLink??? 1286211
???displayArticle.link??? Dev Dyn

Species referenced: Xenopus laevis
Genes referenced: bcl2l11 cdh2 zic1

???attribute.lit??? ???displayArticles.show???

	Fig. 1. Sequences and transfection. A: Nucleotide sequences of the 5' non-coding region of clones 8 and 9. Base homologies are shown by dotted lines. The two arrows delimit the length of the shorter probe (130 pb) used in the second set of Southern blotting experiments. B: Two Southern analysis are performed using genomic DNA and two probes from clone 8 and from clone 9. I: The full-length 5' non-coding region probe (400 pb) was used: genomic DNA (15 pg/lane) was digested with EcoRl (a), Pstl (b), and Pvull (c); II: the 130 pb probe was used; genomic DNA (15 pgllane) was digested with Hindll (d), Hindlll (e), Bam HI (f), and Apal (9). C: Transfection of Xenopus N-cadherin in mouse L cells. a: Non-transfected cells (NT) with fibroblastic morphology; b transfected cells (T) showing epithelioid phenotype, D: Western blot analysis of Ncadherin in tranfected L cells (T) and in control cells (NT) using an antibody agalnst the carboxyterminal region of cadherins. A 11 0 kD band was detected only in transfected cells.
	Fig. 2. Distribution of N-cadherin transcripts in early stages of developrnent. A: Early gastrula (10 NF). 8: Caudal transverse section of a stage 20 NF neurula. C: Transverse section through the anterior trunk region of a late neurula (20-22 NF). The arrowhead points to the pronephric condensation, the arrow to the lateral plate mesoderm. D,E: Details from C. In D, the CNS (arrow) and the notochord (arrowhead) are strongly positive, while the surroundings somites (triangle) are weakly stained. In E, the pronephric anlagen (arrow) expresses N-cadherin transcripts. The overlaying ectoderm and the endoderm are negative. ar, archenteron; bl, blastocoele. A: 250 x : B,D,E: 300 x ; C: 65 x .
	Fig. 3. N-cadherin expression in the CNS, placodes, and mesodermal derivatives. A: Oblique section through the rhombencephalic region of the head in Xenopus tailbud stage (26-27 NF). The rhombencephalon (see also Fig. 5), the optic vesicle (see C), the lens placode (see C), the otic vesicle (arrowhead), the notochord, and the hyoid segment (arrow) show strong hybridization with the N-cadherin probe. 5: Transverse section through the trunk of the same embryo. Note the intense N-cadherin expression in the spinal chord (arrow) and in the notochord (arrowhead) compared to the weak staining of the surrounding somites and epidermis. C: Detail of A. The eye cup with invaginated retinal layer is homogeneously labeled and the lens rudiment (arrow) is still part of the sensorial layer of the ectoderm. Epidermis and neural crest cells (arrowhead) are negative. D: Transverse section through the retina of a stage 42 NF Xenopus tadpole. The three layers of neurona! cell bodies express Ncadherin transcripts; very few grains are visible in the inner and outer plexiform layers and in the outer segment of the photoreceptors. At the periphery, where layers have not yet formed, expression of N-cadherin RNAs is higher (arrow). Note the surrounding black pigmented retinal epithelium (PE). E: Transverse section of the retina of a Xenopus late tadpole (50 NF). Layers of cell bodies hybridize with N-cadherin probe. F: The olfactory placode of a stage 42 Xenopus tadpole expresses high levels of N-cadherin RNAs (arrowhead). In the connecting double-layered epidermis, very few grains are present only in the sensorial layer (arrows). G: Parasagittal section of a Xenopus tailbud (31/32 NF) showing a weak labeling in the myotomes. Elongated mononucleated myoblasts (arrow) lie parallel to the axis. H: Xenopus late tailbud (42 NF) showing numerous grains in myoblasts and myotube forming cells (arrow) and virtually no reaction in the epidermis (arrowhead). GCL: ganglion cell layer; IPL: inner plexiform layer; INL: inner nuclear layer; OPL: outer plexiform layer; ONL: outer nuclear layer; 0s: outer segment of the photoreceptors; PE: pigment retinal epithelium. A,B,C: dark field optic; D,E,F,G,H: bright field optic. A: 65 x ; B-D: 300 x ~ E: 260 x ; F-H: 600 x .
	Fig. 4. Transverse section through the rhombencephalic region of a Xenopus tailbud (26-27 NF). A: The rhombencephalon, the two otic vesicles, the notochord, and the large placode associated with the ear vesicle are positive with N-cadherin probe. 6: Detail of A. Both the otic vesicle and the CNS express high levels of transcrlpts. In the ventromedial region of the otic vesicle (arrowhead) (presumptive sensorial epithe- !ium) and in nerve fiber roots (arrow) the expression of N-cadherin is particularly strong. C: The large IX placode shows high levels of N-cadherin. A: 65 x ; B,C: 300 x .
	Fig. 5. Distribution of N-cadherin transcripts in the CNS of Xenopus from tailbud to tadpole. A: Transverse section showing a very strong hybridization in the roof of the rhombencephalon at tailbud stage 26-27 NF. Compare with the negative overlying ectoderm. 8: Control experiment using sense riboprobe. C: High hybridization is observed in the neural tube and in the notochord of 29-30 NF tailbud. At this stage, the nuclei of the cells have migrated towards the periphery of the notochord where clusters of grains are visible (arrowheads). The somites are stained only very weakly. D: strong reaction in the spinal chord of a stage 42 tadpole. The white matter is faintly labeled (arrow). The large and vacuolated notochord is only stained in limited areas. E: Rhombencephalon, stage 42 NF. The white matter (arrow) is faintly stained while a dense accumulation of grains is seen in the roof of the hindbrain (arrowhead). F: Rhombencephalon, late tadpole (50 NF). A weak expression of cadherin is observed in the gray matter of the brain. The white matter is totally devoid of grains (arrows). G: Olfactory organ, stage 42 NF. High levels of N-cadherin transcripts are seen with a non-uniformed distribution. H: Olfactory organ, stage 50 NF. The gray matter IS still very rich in N-cadherin RNAs. Bright field photomicrographs, 300 x .
	Fig. 6. N-cadherin transcripts in the heart. A: Transverse section of a tailbud (29-30 NF) in which the endocardial tube (arrow) is clearly stained. B: The endocardial tube expresses high levels of N-cadherin transcripts. Note that the rnesocardium (arrow) is also expressing Ncadherin RNAs but to a lesser extent. C: Tailbud (38 NF). Characteristic S shape of the heart anlage. D,E: Tadpole (46-47 NF). The atrium and the ventricle contain numerous red blood cells that do not express Ncadherin transcripts (arrows) while cardiac muscle is strongly positive. Star: pericardial cavity. Dark field photomicrographs. A,D: 65 x ; B,C,E, 300 x ,
	Fig. 7. Other N-cadherin-positive mesodermal derivatives (Stage 26- 27 NF). A: Pronephric anlage located between negative ectodermal and endodermal cells. B: Hyoid arch (arrow) and first branchial arch (arrowhead). Bright field optic, 300 x .
	Fig. 8. Brain and heart of Xenopus tailbud (31-32 NF) stained with probes to two N-cadherin genes. The brain (A,C) and the heart (B,D) express high levels of both N-cadherin transcripts revealed with riboprobes clone 8 (A,B) and clone 9 (C,D). Dark field optic, 300x.