Bloodline Awakening

A clan's bloodline tree has its first node locked behind the awakening. For a clan member that node can't be learned from the menu ("Awakens in battle") and isn't granted by the clan roll.
The trigger: from level 25, each time a player or creature damages you down to 25% of your maximum health or less, there is a chance your bloodline awakens. Whether it does or not, that chance can't come again for 10 minutes of real time (this survives death). Falls, fire, drowning and other damage without an attacker never wake it; self-inflicted damage doesn't count.
On awakening: the tree's first node is learned (and for a release, its release item and advancement are given), with the title "<Tree> awakens" / "Your bloodline answers", the message "On the edge of death, your blood stirs: <Tree> has awakened.", a burst of clan-coloured particles, a beacon sound and a warden heartbeat.
For Uchiha and Hyuga this awakens the Sharingan / Byakugan eye node; for Yamanaka, the Mind Transfer node.

DNA and Clan Locks

Instead of waiting for the awakening, you can have the bloodline's DNA injected by a Ninja Scientist, whatever your clan.
Non-members who look at a clan root on the Jutsu page are told "Needs its DNA". Kekkei genkai roots are marked with their clan, but DNA injection grants the root directly, so outsiders can awaken them by DNA, and the trees' later nodes have no clan lock.
Clan locks that do apply:

The Yamanaka tree has no DNA item and its nodes are locked to Yamanaka, so only a Yamanaka's bloodline awakening opens it.
The Sharingan and Byakugan roots are locked to Uchiha and Hyuga; outsiders use Eye DNA instead.
A Mangekyo Sharingan can't be learned from the menu by anyone; it awakens when a squadmate dies near your open three-tomoe Sharingan, or comes with an implanted Mangekyo eye.

There is no Uzumaki clan in the roll: Uzumaki Sealing is opened by Sealing DNA, for anyone.