H2Av810 is genetically not a null mutation: H2Av810 homozygotes survive into the late larval stages whereas H2AvKO homozygotes die earlier with very small imaginal discs.
Clonal analyses in imaginal discs show that H2Av810 homozygous cells keep proliferating to form clones.  We have been unable to observe clones of H2AvKO homozygous cells, suggesting that the mutant cells die or are eliminated due to cell competition.