Decrease in prosaposin in the Dystrophic mdx mouse brain.
BACKGROUND
Duchenne muscular dystrophy caused by a mutation in the X-linked dystrophin gene induces metabolic and structural disorders in the brain. A lack of dystrophin in brain structures is involved in impaired cognitive function. Prosaposin (PS), a neurotrophic factor, is abundant in the choroid plexus and various brain regions. We investigated whether PS serves as a link between dystrophin loss and gross and/or ultrastructural brain abnormalities.


RESULTS
The distribution of PS in the brains of juvenile and adult mdx mice was investigated by immunochemistry, Western blotting, and in situ hybridization. Immunochemistry revealed lower levels of PS in the cytoplasm of neurons of the cerebral cortex, hippocampus, cerebellum, and choroid plexus in mdx mice. Western blotting confirmed that PS levels were lower in these brain regions in both juveniles and adults. Even with low PS production in the choroids plexus, there was no significant PS decrease in cerebrospinal fluid (CSF). In situ hybridization revealed that the primary form of PS mRNA in both normal and mdx mice was Pro+9, a secretory-type PS, and the hybridization signals for Pro+9 in the above-mentioned brain regions were weaker in mdx mice than in normal mice. We also investigated mitogen-activated protein kinase signalling. Stronger activation of ERK1/2 was observed in mdx mice, ERK1/2 activity was positively correlated with PS activity, and exogenous PS18 stimulated both p-ERK1/2 and PS in SH-SY5Y cells.


CONCLUSIONS
Low levels of PS and its receptors suggest the participation of PS in some pathological changes in the brains of mdx mice.
Department of Anatomy and Embryology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan ; College of Life and Health Sciences, Northeastern University, Shenyang, China.
Hui-Ling
HL
Gao
Cheng
C
Li
Hiroaki
H
Nabeka
Tetsuya
T
Shimokawa
Naoto
N
Kobayashi
Shouichiro
S
Saito
Zhan-You
ZY
Wang
Ya-Ming
YM
Cao
Seiji
S
Matsuda
D000367:Age Factors; D000818:Animals; D002531:Cerebellum / Q000378:metabolism / Q000473:pathology; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology; D002831:Choroid Plexus / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D016189:Dystrophin / Q000172:deficiency / Q000235:genetics*; D005786:Gene Expression Regulation; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008297:Male; D051379:Mice; D018101:Mice, Inbred mdx; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D020388:Muscular Dystrophy, Duchenne / Q000134:cerebrospinal fluid / Q000235:genetics* / Q000473:pathology; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D049231:Saposins / Q000172:deficiency / Q000235:genetics*; D015398:Signal Transduction
D016189:Dystrophin; C483344:Psap protein, mouse; D049231:Saposins; C085339:apo-dystrophin 1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3