How to extend a Ionic component

How can I extend a <ion-item> Ionic component

<ion-list>
  <ion-item>
    <ion-thumbnail item-start>
      <img src="img/thumbnail-totoro.png">
    </ion-thumbnail>
    <h2>My Neighbor Totoro</h2>
    <p>Hayao Miyazaki • 1988</p>
    <button ion-button clear item-end>View</button>
  </ion-item>
</ion-list>

Extending the component to let's say a custom one <custom-ion-item> and extending the logic and template?

Any help appreciated!