The megencephaly mouse has disturbances in the insulin-like growth factor (IGF) system.
Megencephaly, enlarged brain, is a major sign in several human neurological diseases. The mouse model for megencephaly, mceph/mceph, has an enlarged brain and a lowered body weight. In addition, it displays several neurological and motoric disturbances. Previous studies suggest that the brain enlargement results from hypertrophy of the brain cells, rather than hyperplasia. No structural abnormalities, edema or increased myelination have been found. In this study, a major imbalance in the mRNA expression of molecules in the insulin-like growth factor (IGF) system was found in brains of 9-10 weeks old mceph/mceph mice compared to +/+ wild-type mice. In mceph/mceph brains, we found upregulation of IGF binding proteins (BP)-2, -4, -5, and -6 mRNA, the regulating hormone transforming growth factor (TGF)beta1 mRNA and also a local downregulation of IGFBP-5 mRNA compared to wild-type brains by in situ hybridization. The altered expression of these mRNA species is colocalized in cerebral cortex, hippocampus, amygdala and piriform/entorhinal cortex. The mceph/mceph mice express less of the myelin component proteolipid protein (PLP) mRNA in corpus callosum. No expression difference of the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in brain or IGF system components in liver was found between mceph/mceph and wild-type mice. These data suggest that the IGF system has an important role in the excessive growth of the mceph/mceph brains.
Petersson
S
S
Neurogenetics Unit, Center for Molecular Medicine, Karolinska Institutet, L8:00, 171 76, Stockholm, Sweden.
Sandberg Nordqvist
A
A
Schalling
M
M
Lavebratt
C
C
D000679:Amygdala / Q000378:metabolism; D000818:Animals; D001835:Body Weight / Q000235:genetics; D001921:Brain / Q000002:abnormalities*; D000013:Congenital Abnormalities / Q000235:genetics; D003337:Corpus Callosum / Q000378:metabolism; D018728:Entorhinal Cortex / Q000378:metabolism; D005260:Female; D006624:Hippocampus / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000172:deficiency / Q000235:genetics; D018969:Insulin-Like Growth Factor Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008818:Mice, Neurologic Mutants; D018991:Myelin Proteolipid Protein / Q000172:deficiency / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics
D018975:Insulin-Like Growth Factor Binding Protein 5; D018969:Insulin-Like Growth Factor Binding Proteins; D018991:Myelin Proteolipid Protein; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I