Participates in pre-mRNA U12-dependent splicing, performed by the minor spliceosome which removes U12-type introns. U12-type introns comprise less than 1% of all non-coding sequences. Component of the U11/U12 snRNPs that are part of the U12-type spliceosome. Widely expressed until 24 hours post-fertilization (hpf), probably due to inheritance of maternal transcripts. Expression becomes restricted to lens, pharyngeal region, liver/pancreas anlage and intestine at 48-72 hpf. Strongly expressed in pancreas and intestine at 96-120 hpf. Larval lethal with complete lethality by 10 days post-fertilization. Development of multiple organs is affected. Head, eye, lens, pancreas and liver are smaller than normal, and the swim bladder fails to inflate. The intestinal epithelium also remains thin and unfolded. U12-type introns are retained in mRNAs, whereas excision of U2-type introns is not affected. Assembly of both U12- and U11-containing snRNP complexes may be abnormal. Gene expression levels are broadly impacted; effects are not limited to U12-type intron-containing genes.