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Figure 1: The TMEM 138 and TMEM 216 genes and conservation
The authors noted that mutations in either TMEM 138 or TMEM 216 lead to Joubert Syndrome (JBTS). This observation prompted them to examine the strucutre of the genes and their conservation.
Image from Lee et al., 2012
Panel A: The authors present here the structures of TMEM138 and TMEM216. They are located adjacent to one another in the JBTS2 locus of chromosome 11 and are separated by 23 kb. They are transcribed in the same direction and both encode transmembrane proteins. The exons and introns of the genes and the functional properties of different protein segments are also shown.
Panel B: This panel shows the conservation of TMEM138, TMEM216, and the intergenic region separating them. Conservation of both the genes and the intergenic region diminishes with evolutionary distance from humans. Of note, although the adjacency of the two genes is conserved in reptiles and mammals, the genes are not adjacent in amphibians or fish.
Conclusions: The adjacent localization of TMEM138 and TMEM216 is conserved and the result of a chromosomal rearrangement occuring during the evolution of reptiles from amphibians. This observation prompted them to test how this chromosomal rearrangment may have affected the genes' relative expression patterns. That data is shown in Figure 2.
Reference:
Lee, J.H., Silhavy, J.L., Lee, J.E., Al-Gazali, L., Thomas, S., Davis, E.E., Bielas, S.L., Hill, K.J., Iannicelli, M., Brancati, F., Gabriel, S.B., Russ, C., Logan, C.V., Sharif, S.M., Bennett, C.P., Abe, M., Hildebrandt, F., Diplas, B.H., Attie-Bitach, T., Katsanis, N., Rajab, A., Koul, R., Sztriha, L., Waters, E.R., Ferro-Novick, S., Woods, C.G., Johnson, C.A., Valente, E.M., Zaki, M.S., Gleeson, J.G. 2012. Evolutionarily Assembled cis-Regulatory Module at a Human Ciliopathy Locus. Science. 335: 966-969.
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