Okado H and Okamoto H (1992), A Xenopus homologue of the human beta-amyloid p...

XB-ART-23068

Biochem Biophys Res Commun 1992 Dec 30;1893:1561-8.

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A Xenopus homologue of the human beta-amyloid precursor protein: developmental regulation of its gene expression.

Okado H , Okamoto H .

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Complimentary DNA clones have been isolated from Xenopus larva to delineate a protein highly homologous to the human beta-amyloid precursor protein (APP). Developmental change of Xenopus APP gene expression has been analyzed with molecular probes. From early oogenesis, there is a high accumulation of maternal APP. After fertilization, the mRNA is degraded, reaching a minimum level around the gastrula stage. Then zygotic transcription appears to be initiated, and this continues during the subsequent embryonic and larval stages. Splicing patterns differ between the maternal and zygotic transcripts. The ratio of mRNA including the protease inhibitor domain (PID) sequence is extremely low for the transcript of maternal origin as compared to that for the transcript of zygotic origin. These results suggest some roles for the APP molecule in Xenopus early development.

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Species referenced: Xenopus
Genes referenced: app

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	Fig. 1. Xenopus APP nucleotide sequence and deduced amino acid sequence (single-letter code).
	m Comparison of Xenopus APP protein sequence (top line) and human APP 75 1 (bottom line). A vertical line indicates amino acid identity, whereas a dot indicates a conservative change. The PID region is underlined. The location of the p-protein region is shown by a double underline.

	Fig. 4. Northern blotting analysis of the total RNA (30 &lane) from Xenopu,s one-cell stage embrvo and oocvtes. 1. one-cell stage: 0. untreated full-grown oocvte: Odl. full-mown oocy& defollicuiated by ‘treating with”cbllagenase for one “hour; Od2: full-grown Gocyte defolliculated with collagenase overnight; Od3, full-grown oocyte defolliculated with collagenase overnight and then pronase for 3 hours; Om, matured oocyte obtained by treating defolliculated full-grown oocyte (Od2) with progesterone; Oy, young oocytes (oocyte stage I- 4) defolliculated with collagenase overnight.
	m PCR analysis of the splicing pattern of APP mRNA. In A, the strategy is shown schematicallv. When the mRNA contains PID, products a (383 bp) and c (673 bp) will be produced in ihe presence of a pair of sense and at&sense primers (51 and 106) and of a pair of sense and antisense primers (11 and 106), respectively. When the mRNA does not contain PID, products b (215 bp) and d (505 bp) will be produced in the presence of primers 51 and 106 and of primers 11 and 106, respectively (see MATERIALS AND METHODS). In B and C, PCR products with primers 51 and 106 were electrophoresed from lanes l-5. PCR products with primers 11 and 106 were electrophoresed from lanes 6-9. Lane M: DNA size marker, pGEM DNA Markers of Promega (2645, 1605, 1198,676,517,460, 396, 350, 222, and 179). Lane 1: PCR product from the plasmid containing clone KB2, which has PID; this is a positive control for the mRNA containing PID. Lanes 2 and 6: the PCR product from the plasmid containing clone 22, which does-not contain PID (see text); this is-a positive controi for the mRNA without PID. Lane C: PCR product from water with primers 11 and 106; this is the negative control without the template DNA. Lanes 3 and 7: total RNA of stage-42 tadpoles. Lanes 4 and 8: total RNA of gastrula embryos. Lanes 5 and 9; total RNA of full-grown oocytes. In C, 3-fold higher amounts of the PCR product were loaded in lanes 4, 5, 8 and 9.