Thetargeting vector was constructed with the cre/ERT2 gene knocked into the initiator methionine of mouse ASIC4 to replace first 267 amino acid peptides in the N-terminus of ASIC4. A pGK-neo selection cassette flanked by loxP sites was placed downstream of the polyadenylation signal of cre/ERT2. The floxed-pGK-neo cassette was removed by crossing with cre expressing mice. It is a null allele.