Fig. 1

Murine D6Ertd527e gene characterization. a Scheme of the gene and alternative transcripts in mouse oocytes. Shown is a modified UCSC genome browser snapshot depicting expression in the oocyte, three alternative 5′ exons, and the common 3′ exon. The red rectangle depicts position of the MTD LTR insert providing the dominating oocyte-specific promoter and the first exons. The blue rectangle depicts CDS overlapping with a CAG repeat expansion. Dashed line indicates level of 250 counts per million (CPM) in RNA-seq data from C57Bl/6 fully-grown GV oocytes [27]. b Conservation of selected D6Ertd527e sequences in species having the MTD LTR insertion. The left alignment of sequences shows an MTD region carrying the AUG codon, the putative coding part of the 5′ exon, and the splice donor. The right alignment of sequences shows the splice acceptor sequence and beginning of the 3′ exon. In bold font are sequences from species where RNA-seq data are available. Colored in brown and yellow are exon and intron sequences, which were validated by RNA-sequencing. In red are depicted two notable mutations. Homologous sequence of the splice acceptor in Ondatra was not reliably determined. c Adapted timetree [28] of selected rodent species showing basic taxonomic grouping and their phylogenetic relationship. Red lines depict a part of the phylogenetic tree associated with D6Ertd527e MTD LTR in extant genomes. Grey lines lead to species, where the MTD LTR insertion was lost by deletion. The timetree was generated by the TimeTree of Life 5 resource [29]. The timescale below the tree is in millions of years ago as approximated by the TimeTree 5 tool. For more precise phylogenetic analysis of muroid species and discussion of divergence dates see [30]. d D6Ertd527e expression in mouse and hamster oocytes and zygotes. Data were compiled from published RNA-seq data from mouse [31, 32] and hamster [33] samples. Replicates were available for hamster data, n = 3, error bars = SD