Organ-specific expression of IGF-I during early development of bony fish as revealed in the tilapia, Oreochromis niloticus, by in situ hybridization and immunohistochemistry: indication for the particular importance of local IGF-I.
The cellular sites of insulin-like growth factor I (IGF-I) synthesis in the early developing tilapia (0-140 days post fertilization, DPF) were investigated. IGF-I mRNA and peptide appeared in liver as early as 4 DPF and in gastro-intestinal epithelial cells between 5-9 DPF. In exocrine pancreas, the expression of IGF-I started at 4 DPF and continued until 90 DPF. IGF-I production was detected in islets at 6 DPF in non-insulin cells and occurred throughout life. In renal tubules and ducts, IGF-I production started at 8 DPF. IGF-I production in chondrocytes had its onset at 4 DPF, was more pronounced in growing regions and was also found in adults. IGF-I mRNA and peptide appeared in the cytoplasm of skeletal muscle cells at 4 DPF. In gill chloride cells, IGF-I production started at 6 DPF. At 13 DPF, IGF-I was detected in cardiac myocytes. IGF-I-producing epidermal cells appeared at 5 DPF. In brain and ganglia, IGF-I was expressed in virtually all neurones from 6 to 29 DPF, their number decreasing with age. Neurosecretory IGF-I-immunoreactive axons were first seen in the neurohypophysis around 17 DPF. Endocrine cells of the adenohypophysis exhibited IGF-I mRNA at 28 DPF and IGF-I immunoreactivity at 40 DPF. Thus, IGF-I appeared early (4-5 DPF), first in liver, the main source of endocrine IGF-I, and then in organs involved in growth or metabolism. The expression of IGF-I was more pronounced during development than in juvenile and adult life. Local IGF-I therefore seems to have a high functional impact in early growth, metabolism and organogenesis.
Berishvili
Giorgi
G
Division of Neuroendocrinology, Institute of Anatomy, University of Zürich, Zürich, Switzerland.
Shved
Natallia
N
Eppler
Elisabeth
E
Clota
Frederic
F
Baroiller
Jean-François
JF
Reinecke
Manfred
M
D000825:Animal Structures / Q000196:embryology / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000196:embryology / Q000378:metabolism; D002356:Cartilage / Q000196:embryology / Q000378:metabolism; D041981:Gastrointestinal Tract / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D005880:Gills / Q000196:embryology / Q000378:metabolism; D006321:Heart / Q000196:embryology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis* / Q000235:genetics; D007668:Kidney / Q000196:embryology / Q000378:metabolism; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D009132:Muscles / Q000196:embryology / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D009928:Organ Specificity; D010179:Pancreas / Q000196:embryology / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D012867:Skin / Q000196:embryology / Q000378:metabolism; D017210:Tilapia / Q000196:embryology / Q000378:metabolism*
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I