The insertion of Velocigene cassette ZEN-Ub1 created a deletion of size 23547bp between positions 34783423-34806969 of Chromosome 17 (Build GRCm39). The entire coding region was replaced with a lacZ/neo cassette inserted between the start and stop codons, thus creating a null allele. Whole-mount immunofluorescence confirmed detection of anti-NOTCH4 extracellular domain reactivity in the vasculature of wild-type but not homozygous mutant P5 retinas. (J:136110, J:212472)