The N-myc proto-oncogene and IGF-II growth factor mRNAs are expressed by distinct cells in human fetal kidney and brain.
We studied the expression of the N-myc proto-oncogene and the insulin-like growth factor-II (IGF-II) gene in human fetuses of 16-19 gestational wk. Both genes have specific roles in the growth and differentiation of embryonic tissues, such as the kidney and neural tissue. Since continued expression of N-myc and IGF-II mRNAs is also a characteristic feature of Wilms' tumor, a childhood neoplasm of probable fetal kidney origin, we were particularly interested in the possibility that their expression might be linked or coordinately regulated in the developing kidney. Expression of N-myc mRNA was observed in the brain and in the kidney by Northern hybridization analysis. In in situ hybridization of the kidney, N-myc autoradiographic grains were primarily located over epithelially differentiating mesenchyme while most of the mesenchymal stromal cells showed only a background signal with the N-myc probe. N-myc mRNA was detectable throughout the developing brain with a slight accentuation in the intermediate zone cells in between the subependymal and cortical layers. Thus, even postmitotic neuroepithelial cells of the fetal cerebrum expressed N-myc mRNA. In Northern hybridization, IGF-II mRNA signal was abundant in the kidney but much weaker, though definite, in the brain. The regional distribution of IGF-II mRNA in the kidney was largely complementary to that of N-myc. IGF-II autoradiographic grains were located predominantly over the stromal and blastemal cells with a relative lack of hybridization over the epithelial structures. In the brain, IGF-II mRNA was about two- to threefold more abundant in the subependymal and intermediate layers than in the cortical plate and ependymal zone, respectively. The fetal expression patterns of the N-myc and IGF-II mRNAs are reflected by the types of tumors known to express the corresponding genes during postnatal life such as Wilms' tumor. However, the apparent coexpression of the IGF-II and N-myc genes in immature kidneys occurs largely in distinct cell types.
Hirvonen
H
H
Department of Virology, University of Turku, Finland.
Sandberg
M
M
Kalimo
H
H
Hukkanen
V
V
Vuorio
E
E
Salmi
T T
TT
Alitalo
K
K
D001345:Autoradiography; D001921:Brain / Q000166:cytology / Q000196:embryology*; D001923:Brain Chemistry; D002454:Cell Differentiation; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D007668:Kidney / Q000032:analysis / Q000166:cytology / Q000196:embryology*; D009447:Neuroblastoma / Q000235:genetics; D009693:Nucleic Acid Hybridization; D000090063:Proto-Oncogene Mas; D011519:Proto-Oncogenes; D012333:RNA, Messenger / Q000235:genetics*; D012160:Retina / Q000032:analysis / Q000196:embryology; D013002:Somatomedins / Q000235:genetics*; D009396:Wilms Tumor / Q000235:genetics
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger; D013002:Somatomedins; D007335:Insulin-Like Growth Factor II