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. 2008 May 1;22(9):1141–1146. doi: 10.1101/gad.473408

Figure 1.

Figure 1.

Gene structure and CpG methylation at the murine H13/Mcts2 locus. (A) Transcript map of H13 isoforms, determined by 5′ and 3′ RACE, Northern, and GenBank EST evidence. The bar indicates nucleotide position on mouse Chromosome 2 (Mm. build 37). Representative GenBank accession numbers are as follows: H13a 1.8 kb, AJ345032; H13a 2.0 kb, AK049101; H13b, NM_010376; H13c, F830002G13; H13d, 4021402J09; H13e, AK004690; Mcts2, NM_025543. Exons are black rectangles and splice patterns are indicated. Vertical arrows indicate polyA sites, and horizontal arrows show the direction of transcription. The greater abundance of H13a prevented the simultaneous detection of H13a, H13b, and H13c in a single 3′ RACE reaction. Consequently, we did not determine whether the alternatively skipped penultimate exon is also included in H13b or H13c transcripts. The positions of Northern probes for C are shown at the bottom, as are the three CpG islands at which methylation was investigated in D. (B) Predicted structure of proteins translated from H13 transcript isoforms. Cylinders represent transmembrane (TM) helices. Residues critical for signal peptide peptidase activity are indicated within transmembrane helices 4 and 5. Distinct C termini for H13a–c protein isoforms arise from the inclusion or exclusion of a penultimate exon (see the text). Membrane topology for the larger protein was determined by Weihofen et al. (2002). The proteins putatively translated from H13d and H13e have not been described previously; hence, membrane topology is not shown. (C) Northerns performed with neonatal brain mRNA identify transcripts utilizing all five polyA sites identified by 3′ RACE. (D) DNA methylation at three CpG islands: the H13 promoter, the Mcts2 promoter, and the H13 downstream. Horizontal lines denote individual DNA strands on which filled circles represent methylated CpG dinucleotides; open circles are unmethylated CpGs. Genomic DNA was extracted from whole brain of neonatal mice carrying uniparental partial duplications for distal Chromosome 2 [MatDp(dist2) and PatDp(dist2)].