The expression pattern of an insulin-like growth factor (IGF)-binding protein gene is distinct from IGF-II in the midgestational rat embryo.
Insulin-like growth factor-II (IGF-II), the predominant form of IGF in fetal and neonatal serum and tissues, is found in vivo complexed with IGF-binding proteins. One of these binding proteins, IGFBP-2, is present at high levels in fetal rat plasma and binds both IGF-I and IGF-II with high affinity. We here have used in situ hybridization to compare the distribution of IGFBP-2 mRNA with that of IGF-II mRNA in embryonic day 13.5-15 rat embryos. The spatial patterns of IGF-II and IGFBP-2 expression in the fetal trunk were distinct and, in general, nonoverlapping. Most mesoderm derivatives that express IGF-II at high levels contained little, if any, IGFBP-2 mRNA. Instead, IGFBP-2 mRNA was expressed at high levels in many cell types derived from ectoderm and endoderm. The expression of IGFBP-2 mRNA in the central nervous system (CNS) during this developmental period was examined in particular detail. The three most prominent sites of IGFBP-2 expression in the CNS were comprised of cells with nonneuronal phenotypes: 1) the epithelium of the choroid plexus, a tissue that produces cerebrospinal fluid; 2) the floor plate, an area that can guide axonal outgrowth from commissural neurons of the spinal cord in vitro; and 3) the infundibulum, the progenitor of the posterior pituitary that is believed to influence differentiation of the adjacent intermediate pituitary.(ABSTRACT TRUNCATED AT 250 WORDS)
Wood
T L
TL
Department of Anatomy and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York 10032.
Brown
A L
AL
Rechler
M M
MM
Pintar
J E
JE
D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000196:embryology / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics*; D002831:Choroid Plexus / Q000196:embryology / Q000378:metabolism; D004475:Ectoderm / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D005333:Fetus / Q000378:metabolism*; D015870:Gene Expression; D005865:Gestational Age; D018969:Insulin-Like Growth Factor Binding Proteins; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D008648:Mesoderm / Q000378:metabolism; D009693:Nucleic Acid Hybridization; D010902:Pituitary Gland / Q000196:embryology / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000196:embryology / Q000378:metabolism
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D007335:Insulin-Like Growth Factor II