In order to determine the coding sequence for the larger transcript, we searched the mouse EST database using each intron as well as the genomic sequence flanking the Mcoln1 gene. Two ESTs were identified that contained sequence from intron 12 (GB No. AI430291 and AA874645), and the corresponding clones were sequenced. Clone 408619 (ESTs: GB No. AI430291, AI429558) begins approximately 1.1 kb before exon 13 and continues through the exon and splices correctly to exon 14. Clone 1281641 (EST:GB No. AA874645) begins 175 bp before exon 13 and also splices correctly to exon 14. A mouse multiple tissue Northern was hybridized using a probe generated from the putative intron sequence in clone 408619 (Probe 2, Fig. 1B), which detected only the 4.4 kb band (Fig. 3C).