In general, mutual funds such as pension funds, public/gov funds cannot buy a stock that is under 10 bucks or 5 bucks. But many private funds can. Here are a couple of examples: CIEN and ALTH. Both are below 5 or 4, but inst ownership is more than 60% for each. I know Warren Buffet can buy any kind of stock. He bought Level 3 when it was below 2.
When I bought INSM at 1.38 last week (see my previous posts), I knew a few wealth investors (i-hub members) bought at 1.36 too. Again, INSM is not a day-trader's stock. Don't trade INSM. Don't buy INSM on margin. Buy and hold, you will be rewarded in several years.