Surprisingly, Jag1Ndr/Ndr arterioles displayed fewer cCasp3+ ECs at branching points (Fig EV4M) but significantly more cCasp3+ along the arteriole length, often associated with αSMA‐negative areas (Fig 4J, note the aneurysm formation in the αSMA‐negative area). Here, ACTA1 is linked to aneurysm.