Large numbers of novel non-protein-coding RNAs (ncRNAs) have been characterized in worms, plants, insects, and mammals by experimental approaches. However, with the advent of large-scale genome sequencing, especially in humans and mice, literally hundreds of additional ncRNAs of unknown classification and function have been identified. In mice alone, the ncRNAs are thought to represent approximately 1/3 of all transcription units in the genome. ncRNA function remains poorly understood since past research has focused primarily on protein coding genes and the proteome. To begin to close the knowledge gap on these types of transcription units, firstly, bioinformatics-based filtering of mouse putative non coding mRNA-like RNAs identified by RIKEN-FANTOM will be conducted to identify novel candidates for functional studies Secondly, molecular expression analysis of a selected set of ncRNAs will be conducted to identify tissue specific and/or abundantly expressed transcripts. Following from the molecular analysis, a select group of non-coding RNAs will be analyzed by loss-of-function genetics in mice.