Insulin-like growth factor I mRNA levels are developmentally regulated in specific regions of the rat brain.
The expression of mRNAs encoding insulin-like growth factor I (IGF-I) and the IGF-I receptor in the developing rat brain from embryonic day 16 to postnatal day 82 was analyzed using solution hybridization-RNase protection assays. Four distinct developmental patterns in the steady-state levels of IGF-I mRNA were seen. Specifically, the olfactory bulb showed a high perinatal level of IGF-I mRNA which declined dramatically by postnatal day 8. In contrast, cerebral cortex displayed maximal levels of IGF-I mRNA at postnatal day 8 and 13, which subsequently declined to adult levels (P82). A third developmental pattern was seen in the hypothalamus, where IGF-I mRNA increased from E16 up to postnatal day 3 and remained elevated thereafter. Finally, IGF-I mRNA levels in brainstem and cerebellum remained unchanged throughout the time period studied. We conclude that there are specific regional patterns of IGF-I gene expression in the developing rat brain. In contrast, IGF-I receptor gene expression did not exhibit any region-specific developmental changes. The developmental patterns of IGF-I gene expression seen in this study further substantiate the potential role of IGF-I in normal brain development.
Bach
M A
MA
Section of Molecular and Cellular Physiology, NIDDK, National Institutes of Health, Bethesda, MD 20892.
Shen-Orr
Z
Z
Lowe
W L
WL
Roberts
C T
CT
LeRoith
D
D
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000196:embryology / Q000254:growth & development*; D001923:Brain Chemistry; D001931:Brain Mapping; D005786:Gene Expression Regulation; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D011919:Rats, Inbred Strains
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I