ES cells harboring the Zcchc17tm1Pou (which contains a PGK-beta-geo (beta-galactosidase-neomycin fusion gene) selection cassette inserted into exon 4) allele were targeted to insert a PGK-hygromycin cassette into exon 2. Both the ATGs in exon 2 (long isoform) and exon 4 (short isoform) are disrupted. RT-PCR indicates enhanced mRNA expression of a miniform spanning exons 1, 6, and 7 (345 bp), which can produce a peptide from an alternative start codon in exon 7. (J:233160)