Structure and methylation of tammar INS. (A) 5′-Rapid amplification of cDNA ends (5′-RACE) was performed on RNA derived from one pancreas (Panc), two mammary glands (MG) and one liver (Liv). Five INS transcripts were amplified using a primer designed in the first INS coding exon (half-arrow). Three transcripts were chimeras and contained an exon derived from the neighbouring tyrosine hydroxylase (TH) gene and two were transcribed from the INS noncoding exon. The mammary gland 1 (MG1; lactation phase 1) and liver expressed both types of transcripts, the pancreas expressed only the INS-derived transcripts, and the mammary gland 2 (MG2; lactation phase 3) expressed only the TH-INS transcripts. (B) Schematic of predicted tammar TH and INS genes (not to scale). Predicted coding exons (grey), verified coding exons (black) and noncoding exons (white) are represented by boxes. Transcription start sites identified by 5′-RACE are indicated with turned arrows. CpGs are indicated by short vertical black lines. SNPs are indicated by black triangles. Bisulphite sequenced regions (black horizontal lines) are shown with individual bisulphite sequences underneath: open and closed circles are unmethylated and methylated CpGs, respectively. Each row represents the methylation pattern on a separate DNA fragment from the same sample. Both methylated and unmethylated alleles were present in the liver and mammary gland tissues at the TH-INS TSS. Only methylated alleles were present at the CpG Island and the INS TSS had a variable methylation pattern.INS, insulin gene.