How to use jq when the variable has reserved characters?

I'm trying to get the following to work and it's not, help me please:

curl -s 'https://cryptofresh.com/api/asset/markets?asset=MKR' | jq .OPEN.BTC

The variable in question includes a period, I tried just about everything to escape the period && also tried surrounding it in quotes; no go ; this is the variable I'm looking to pull from (I ran jq without any filters, and truncated the output here to show what I need. Thanks in advance future problem solver!

curl -s 'https://cryptofresh.com/api/asset/markets?asset=MKR' | jq...."OPEN.BTC": {"volume24": 0.932166,"price": 0.09995,"updated": "2016-05-04T03:03:29.000Z"},....