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Figure 2: Relative expression patterns of TMEM138 and TMEM 216
To test test how the chromosomal rearrangment described in Figure 1 may have affected the genes' relative expression patterns, the authors analyzed the expression of TMEM138 and TMEM216 in human, mouse, and zebrafish tissues.
Image from Lee et al., 2012
Panel A: The authors used antisense RNA probes to label transcripts for TMEM138 and TMEM216 in human embryonic kidney (kid), adrenal glands (ad), gonads (go), and nervous system (b, d, f). Labeling revealed a very similar expression pattern for both genes in all tissues.
Panel B: The authors used real time quantatative PCR to quantify expression (mRNA) levels of TMEM138 and TMEM216 in mouse and zebrafish tissues. Mouse tissues demonstrated coordinated expression levels of both proteins whereas zebrafish tissues did not.
Data not shown: In supplementary figures, the authors claim to demonstrate that expression of TMEM138 and TMEM216 is regulated by a single regulatory factor, X 4, in mice.
Conclusions: TMEM138 and TMEM216 are closely co-expressed in mice and humans, but not zebrafish, as a result of a common regulatory element. The sharing of this regulatory element is likely a product of TMEM138 and TMEM216's adjacency resulting from the amphibian-to-reptile evolutionary transition. This co-expression suggested to the authors that the genes may subserve similar functions in cells, a possibility they tested in Figure 3.
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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