Repulsive axon guidance molecule Sema3A inhibits branching morphogenesis of fetal mouse lung.
Semaphorin III/collapsin-1 (Sema3A) guides a specific subset of neuronal growth cones as a repulsive molecule. In this study, we have investigated a possible role of non-neuronal Sema3A in lung morphogenesis. Expression of mRNAs of Sema3A and neuropilin-1 (NP-1), a Sema3A receptor, was detected in fetal and adult lungs. Sema3A-immunoreactive cells were found in airway and alveolar epithelial cells of the fetal and adult lungs. Immunoreactivity for NP-1 was seen in fetal and adult alveolar epithelial cells as well as endothelial cells. Immunoreactivity of collapsin response mediator protein CRMP (CRMP-2), an intracellular protein mediating Sema3A signaling, was localized in alveolar epithelial cells, nerve tissue and airway neuroendocrine cells. The expression of CRMP-2 increased during the fetal, neonate and adult periods, and this pattern paralleled that of NP-1. In a two-day culture of lung explants from fetal mouse lung (E11.5), with exogenous Sema3A at a dose comparable to that which induces growth cone collapse of dorsal root ganglia neurons, the number of terminal buds was reduced in a dose-dependent manner when compared with control or untreated lung explants. This decrease was not accompanied with any alteration of the bromodeoxyuridine-positive DNA-synthesizing fraction. A soluble NP-1 lacking the transmembrane and intracellular region, neutralized the inhibitory effect of Sema3A. The fetal lung explants from neuropilin-1 homozygous null mice grew normally in vitro regardless of Sema3A treatment. These results provide evidence that Sema3A inhibits branching morphogenesis in lung bud organ cultures via NP-1 as a receptor or a component of a possible multimeric Sema3A receptor complex.
Ito
T
T
Department of Pathology, Yokohama City University School of Medicine, 3-9 Fuku-Ura, Kanazawa-ku, 236-0004, Yokohama, Japan.
Kagoshima
M
M
Sasaki
Y
Y
Li
C
C
Udaka
N
N
Kitsukawa
T
T
Fujisawa
H
H
Taniguchi
M
M
Yagi
T
T
Kitamura
H
H
Goshima
Y
Y
D000818:Animals; D001369:Axons / Q000502:physiology; D015153:Blotting, Western / Q000379:methods; D005260:Female; D006023:Glycoproteins / Q000235:genetics / Q000502:physiology*; D008168:Lung / Q000196:embryology* / Q000473:pathology; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009024:Morphogenesis; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D039942:Neuropilin-1; D020133:Reverse Transcriptase Polymerase Chain Reaction; D040121:Semaphorin-3A
D006023:Glycoproteins; D009419:Nerve Tissue Proteins; D040121:Semaphorin-3A; D039942:Neuropilin-1