> curl --data @- -X PUT --dump - http://localhost:8529/_api/graph/graph1/vertex/v1
{"optional1" : "val2"}

HTTP/1.1 200 OK
content-type: application/json; charset=utf-8
etag: 24332190

{
  "vertex": {
    "_id": "v/v1",
    "_rev": "24332190",
    "_key": "v1",
    "optional1": "val2"
  },
  "error": false,
  "code": 200
}