Imprinted gene clusters are regulated by long noncoding RNAs (lncRNAs), CCCTC binding factor (CTCF)-mediated boundaries, and DNA methylation. DIRAS3 (also known as ARH1 or NOEY1) is an imprinted gene encoding a protein belonging to the RAS superfamily of GTPases and is located within an intron of a lncRNA called GNG12-AS1. In this study, we investigated whether GNG12-AS1 is imprinted and coregulated with DIRAS3. We report that GNG12-AS1 is coexpressed with DIRAS3 in several tissues and coordinately downregulated with DIRAS3 in breast cancers. GNG12-AS1 has several splice variants, all of which initiate from a single transcription start site. In placenta tissue and normal cell lines, GNG12-AS1 is biallelically expressed but some isoforms are allele-specifically spliced. Cohesin plays a role in allele-specific splicing of GNG12-AS1. In breast cancer cell lines with loss of DIRAS3 imprinting, DIRAS3 and GNG12-AS1 are silenced in cis and the remaining GNG12-AS1 transcripts are predominantly monoallelic. The GNG12-AS1 locus, which includes DIRAS3, provides an example of imprinted cotranscriptional splicing and a potential model system for studying the long-range effects of CTCF-cohesin binding on splicing and transcriptional interference.