Conservation of expression and alternative splicing in the prosaposin gene.
Prosaposin is the precursor of four lysosomal activator molecules known as saposins A, B, C and D. It is also secreted and was proposed to be a neurotrophic factor. The neurotrophic function was attributed to the amino terminus of saposin C. In man, mouse and rat prosaposin is transcribed to two major isoforms differing in the inclusion of 9 bps of exon 8 within the saposin B domain. In the present study, we show that there is evolutionary conservation of the prosaposin structure and alternative splicing in chick and zebrafish as well. Moreover, there is conservation in prosaposin expression as tested immunohistochemically in the mouse and chick developing brain. We developed a sensitive assay to quantitate the prosaposin alternatively spliced forms. Our results indicate that, in mouse brain, skeletal and cardiac muscle the exon 8-containing RNA is most abundant, while it is almost absent from visceral and smooth muscle-containing organs. We observed temporal and differential expression of the alternatively spliced prosaposin mRNAs in mouse and chick brain as well as during development. The elevation in the abundance of exon 8-containing prosaposin RNA during mouse and chick brain development may suggest a role for the exon 8-containing prosaposin form in this process.
Cohen
Tsadok
T
Department of Cell Research and Immunology, Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel.
Ravid
Liat
L
Altman
Netta
N
Madar-Shapiro
Liora
L
Fein
Amos
A
Weil
Miguel
M
Horowitz
Mia
M
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D002642:Chick Embryo; D019143:Evolution, Molecular; D005091:Exons; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D049231:Saposins / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014018:Tissue Distribution
C483344:Psap protein, mouse; D012333:RNA, Messenger; D049231:Saposins