Extended Data Fig. 8: Loss of dietary-related genes in monotremes.

a, Tooth-related gene loss in representative mammals and reptiles. b–f, Potential loss of digestion-related genes in both monotremes shown by whole-genome alignment and read mapping. In each panel there are three lines in the synteny plot, representing the orthologous region of the genes in platypus, human and echidna from top to bottom, respectively. Grey links indicate human–platypus and human–echidna LASTZ alignments. Each rectangle or triangle represents an exon. Fragmented genes are marked by dashed lines. Illumina reads of platypus and echidna are aligned to the platypus or human genome (Ensembl release 87) and the flanking region of each gene is visualized by pyGenomicTrack. GAPDH region is also plotted as a control. g, RT–PCR expression analysis shows expression of NGN3 in brain, stomach, intestine and pancreas of both platypus and echidna. These results are similar to other mammals. This, together with sequencing results, shows that NGN3 in monotremes is present and is likely to be functioning normally. NGN3, NGN3 primers; b-actin, β-actin primers; -ve, negative control, no template; gDNA, genomic DNA template; brain, brain cDNA template; stom, stomach cDNA template; int, intestine cDNA template; panc, pancreas cDNA template. Lanes 1 (top), 1, 8 (middle) and 9 (bottom) are a 100-bp DNA ladder: 1,517, 1,200, 1,000, 900, 800, 700, 600, 500/517, 400, 300, 200 and 100 bp. Expected sizes of PCR products for NGN3 in platypus is 157 bp and for echidna 145 bp, and the PCR product for the β-actin genomic region is 597 bp and cDNA is 348 bp. Silhouettes of human and opossum are from https://www.flaticon.com/. The silhouette of the platypus is created by S. Werning and is reproduced under a Creative Commons Attribution 3.0 Unported licence (http://creativecommons.org/licenses/by/3.0/).