Cre mediated excision resulted in the removal of exon 1 from Klhl1. The deleted sequence contains the CpG-rich promoter region, the transcription initiation site, the first splice donor site, and the first exon portion of the coding frame. The entire genomic sequence transcribed by the Klhl1as and the predicted promoter region were also absent. RT-PCR and Northern blot confirmed the absence of Klhl1 transcript.