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Differential expression of phosphacan/RPTPβ isoforms in the developing mouse visual system
Author(s) -
Klausmeyer Alice,
Garwood Jeremy,
Faissner Andreas
Publication year - 2007
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.21479
Subject(s) - neurite , biology , gene isoform , epitope , microbiology and biotechnology , laminin , chondroitin sulfate , extracellular matrix , biochemistry , genetics , gene , glycosaminoglycan , in vitro , antigen
The chondroitin sulfate proteoglycan DSD‐1‐PG/phosphacan represents one of four splice variants of receptor‐protein‐tyrosine‐phosphatase‐beta/zeta (RPTPβ/ζ). This receptor is expressed by glial cells and occurs in two isoforms, RPTPβ long and RPTPβ short . The secreted forms phosphacan and phosphacan short isoform (PSI) bind to extracellular matrix and adhesion molecules and might mediate astroglial effects on neuronal differentiation. Phosphacan and RPTPβ long both carry the DSD‐1 epitope, a glycosaminoglycan modification that is involved in stimulating neurite outgrowth of embryonic rat mesencephalic and hippocampal neurons in a polycationic environment. Additionally, phosphacan inhibits neurite outgrowth of embryonic DRG neurons in the presence of laminin. In the light of these functional properties we examined the expression patterns of the DSD‐1 epitope and phosphacan isoforms in the developing mouse visual system. During retinal development the DSD‐1 epitope appears around embryonic day (E)13, peaks around postnatal day (P)6, and is downregulated from P9 to adolescence. By comparison, the phosphacan core protein is first detectable at E12, reaches maximal levels around P14, and persists, although at lower levels, to adulthood. The DSD‐1 epitope is restricted to the nerve fiber and the inner plexiform layers. In contrast, the phosphacan core protein immunoreactivity extends from the nerve fiber layer to the outer plexiform layer. The level of expression of the phosphacan/RPTPβ gene was investigated by reverse‐transcriptase polymerase chain reaction. These experiments suggest that there is a shift in the expression patterns of the different phosphacan/RPTPβ isoforms during late embryonic and postnatal development. In situ hybridization experiments support the conclusion that at least one of the phosphacan/RPTPβ isoforms in the retina is expressed by neurons. J. Comp. Neurol. 504:659–679, 2007. © 2007 Wiley‐Liss, Inc.