AGE-DEPENDENT INHIBITION OF NEURAL CREST MIGRATION BY THE NOTOCHORD CORRELATES WITH ALTERATIONS IN THE S103L CHONDROITIN SULFATE PROTEOGLYCAN

In avian embryos, the notochord inhibits neural crest migration, resul ting in the absence of neural crest cells from the perinotochordal spa ce. Here, we test whether temporal changes in the ability of the notoc hord to inhibit neural crest migration correlate with alterations in t he S103L chondroitin sulfate proteoglycan (CSPG). Because CSPGs are ab undant in the perinotochordal space and the inhibitory effects of the notochord are chondroitinase sensitive both in vivo and in vitro, we e xamined the distribution and biochemical nature of a large CSPG whose core protein is recognized by the S103L antibody. The S103L CSPG is sp ecific to the perinotochordal space during the course of neural crest migration and codistributes with the HNK-1 carbohydrate. Biochemical c haracterization reveals that the S103L CSPG bears the HNK-1 epitope an d is the only HNK-1 immunoreactive proteoglycan present around the not ochord at these stages, Following neural crest migration, the S103L CS PG staining is maintained in the perinotochordal region and also is ex pressed later in cartilage. In 4-day-old embryos, however, the S103L C SPG undergoes a reduction of HNK-1 immunoreactivity. To examine the te mporal nature of the notochord's inhibitory ability, we assayed the ef fects on neural crest migration of grafting notochords from 2- to 5-da y-old donor quail embryos into 2-day-old host chick embryos. Donor not ochords from 2- to 3-day-old embryos inhibit neural crest cell migrati on, whereas the degree of inhibition is reduced or absent when notocho rds are derived from greater than or equal to 4-day-old donors. This s uggests that older notochords lose their inhibitory ability. Interesti ngly, preincubation of younger notochords with the HNK-1 antibody bloc ks the inhibitory effect, suggesting that glycosylation of the perinot ochordal matrix may be important, The time when the notochord loses it s inhibitory ability as assessed by our in vivo grafting assay correla tes with the biochemical and immunocytochemical changes in the notocho rdal S103L antigen. These data suggest that a species of S103L CSPG, w hich is expressed by the early notochord and bears the HNK-1 epitope, may be important for the inhibition of neural crest migration. (C) 199 6 Academic Press, Inc.