Characterization of L1 at 1p22.3. (a) Diagram of L1 at 1p22.3 and the surrounding region. The arrow designates the L1 transcript. Triangles at F and R indicate positions of oligonucleotides 1p22.3F and 1p22.3R. Blue boxes indicate exons of nearest genes SH3GLB1 and CLCA, with exon number designated. The sequence of the 3' expression tag is provided. (b) Relative expression of the L1 at 1p22.3 in lymphoblastoid cell lines from CEPH individuals. Expression is in arbitrary units normalized to HPRT1. Error bars indicate ± standard deviation from three replicates. All data are representative of at least two biological replicates. (c) Bisulfite sequencing of amplicon surrounding the start of transcription of the L1 at 1p22.3 in GM10860, GM11992 and GM11993. Each circle represents a single CpG, while each row is an individual sequence clone. The position of the start of transcription as determined by 5' RACE is indicated. Filled circles indicate lack of bisulfite conversion - that is, cytosine methylation. Grey circles indicate residues that could not be assigned due to sequence polymorphism or poor sequence quality. The CpG at position -120 is unmethylated in the majority of clones from all three individuals.