Large interrelated clusters of repetitive elements (REs) and RE arrays predominantly represent reference mouse chromosome Y

The vast majority of the mouse and human genomes consist of repetitive elements (REs), while protein-coding sequences occupy only ∼3 %. It has been reported that the Y chromosomes of both species are highly populated with REs although at present, their complete sequences are not available in any public database. The recent update of the mouse genome database (Build 38.1) from the National Center for Biotechnology Information (NCBI) indicates that mouse chromosome Y is ∼92 Mb in size, which is substantially larger than the ∼16 Mb reported previously (Build 37.2). In this study, we examined how REs are arranged in mouse chromosome Y (Build 38.1) using REMiner-II, a RE mining program. A combination of diverse REs and RE arrays formed large clusters (up to ∼28 Mb in size) and most of them were directly or inversely related. Interestingly, the RE population of human chromosome Y (NCBI Build 37.2-current) was less dense, and the RE/RE array clusters were not evident in comparison to mouse chromosome Y. The annotated gene loci were distributed in five different regions and most of them were surrounded by unique RE arrays. In particular, tandem RE arrays were embedded into the introns of two adjacent gene loci. The findings from this study indicate that the large and interrelated clusters of REs and RE arrays predominantly represent the unique organizational pattern of mouse chromosome Y. The potential interactions among the clusters, which are populated with various interrelated REs and RE arrays, may play a role in the structural configuration and function of mouse chromosome Y.