Identification of three prominin homologs and characterization of their messenger RNA expression in Xenopus laevis tissues

[摘要] Purpose: Prominin is a family ofpentaspan transmembrane glycoproteins. They are expressed in varioustypes of cells, including many stem/progenitor cells. Prominin-1 playsan important role in generating and maintaining the structure of thephotoreceptors. In this study, we identified three prominin homologs inXenopus laevis, a model animal widely used in vision research,and characterized their messenger RNA (mRNA) expression in selectedtissues of this frog. Methods: Reverse-transcription PCR(RT–PCR) and rapid amplification of cDNA ends (RACE) were used toisolate cDNAs of prominin homologs. Semiquantitative RT–PCR was used tomeasure the relative expression levels of mRNAs of the three promininhomologs in four X. laevis tissues, specifically those of theretina, brain, testis, and kidney. Sequences of prominin homologs wereanalyzed with bioinformatic software. Results: We isolated cDNAs of threeprominin homologs from X. laevis tissues and compared theirsequences with previously described prominin-1, 2, and 3 sequences fromother species using phylogenetic analysis. Two of these homologs arelikely to be the X. laevis orthologs of mammalian prominin-1and 2, respectively, while the third homolog is likely to be the X.laevis ortholog of prominin-3, which was only found in nonmammalianvertebrates and the platypus. We identified alternatively spliced exonsin mRNAs of all three prominin homologs. Similar to mammalianprominin-1, we found that exons 26b, 27, and 28a of the X. laevisprominin-1 gene are alternatively spliced, and that the splice isoformsof mRNA show tissue-specific expression profiles. We found thatprominin-1 was the most abundant homolog expressed in the retina,brain, and testis, while prominin-3 was the most abundant homolog inthe kidney. The expression level of prominin-2 was the lowest of thethree prominin homologs in all four examined tissues of this frog. Conclusions: Our results suggest thatthe mRNAs of prominin homologs are expressed in many tissues of X.laevis, but differ in their expression levels and mRNA splicing.Prominin-1 is the most abundant of the three prominin homologsexpressed in the frog retina.

[学科分类] 生物化学/生物物理