High impact information on NRP1

• Neuropilin, a previously cloned transmembrane protein, has recently been identified as a candidate receptor for collapsin-1 [1].
• In birds, neuropilin-1 was expressed by arterial endothelium and wall cells, but absent from veins [2].
• Interestingly, with the reduction of neuropilin-1 function, neural crest cells still form segmental migratory streams, suggesting that initial neural crest cell migration and invasion of the branchial arches are separable processes [3].
• Time-lapse imaging shows that neuropilin-1 siRNA transfected neural crest cells stop and collapse filopodia at the 2nd branchial arch entrances, but do not die [3].
• In vivo analysis reveals a critical role for neuropilin-1 in cranial neural crest cell migration in chick [3].

Biological context of NRP1

• Expression of a cell adhesion molecule, neuropilin, in the developing chick nervous system [4].
• The predicted amino acid sequence of chick neuropilin is 75% identical to that of the Xenopus homologue [4].
• A cell aggregation assay showed that fibroblasts transfected with the chick neuropilin cDNA acquired cell adhesiveness [4].
• By using small inhibitory hairpin RNA (siRNA) molecules generated by the mouse U6 promoter, we have applied an RNA interference approach to achieve quantitative knockdown of the neuropilin-1 (Nrp-1) receptor in chick embryos [5].
• In tadpoles after stage 50, the binding of MAbA5 to the optic nerves was extremely weak or almost nil, although RGCs expressed considerable amounts of neuropilin mRNA [6].

Anatomical context of NRP1

• Neuropilin (previously known as the A5 protein) is a membrane protein identified in Xenopus and is presumed to be involved in the target recognition of the optic nerve fibers [4].
• Cultured neurons of the dorsal root ganglia express chick neuropilin on their neurites including growth cones [4].
• This adhesion is mediated by a heterophilic interaction between neuropilin and protease-sensitive molecules on fibroblasts [4].
• Together these results suggest that NRP1 might have a dual function in bone by mediating osteoblast function directly as well as angiogenesis [7].
• On the other hand, NRP1 was not expressed by osteocytes in either species, consistent with the in vitro results [7].

Other interactions of NRP1

• Consistent with the insensitivity of trkC(+) collaterals to SEMA3A, these collaterals did not express neuropilin-1, a receptor for SEMA3A [8].

Analytical, diagnostic and therapeutic context of NRP1

• Arterial-venous differentiation and patterning are controlled by hemodynamic forces, as shown by flow manipulation and in situ hybridization with arterial markers ephrinB2 and neuropilin 1, which show that expression of both mRNAs is not genetically determined but plastic and regulated by flow [9].
• We investigate the role of a potential guidance factor, neuropilin-1, and use functional knockdown assays, tissue transplantation and in vivo confocal time-lapse imaging to analyze changes in chick cranial neural crest cell migratory patterns [3].
• Using cocultures composed of tissues derived from chick embryos or neuropilin-1-deficient mice treated with chondroitinase ABC, we show the direct evidence that CSPGs are involved in notochord-derived repulsion for DRG axons [10].
• Expression of the ligands Sema3A and -3E and the receptors neuropilin Npn-1, -2a and -2b in the chick visual system were analyzed by RT-PCR [11].

References