The <i>tnfaip8</i> gene was lost in a genome inversion event after the divergence of the teleost and spotted gar lineages.

<p><i>TNFAIP8</i> is flanked by <i>DMXL1</i> and <i>HSD17B4</i> in (A) humans and rayfin fishes that diverged before the teleost genome duplication like the (D) spotted gar. The three genes are transcribed in the same direction in both human and gar genomes. In teleosts including (B) zebrafish and (C) stickleback, <i>tnfaip8</i> is missing and <i>dmxl1</i> and <i>hsd17b4</i> are transcribed in opposite directions. (E, F) Dre8 and Hsa5 share conserved synteny in the region surrounding <i>TNFAIP8</i>. Crossing lines indicate shifts in gene order consistent with a chromosome inversion event. The other breakpoint for the inversion occurred between <i>hsd17b4</i> and <i>prr16</i>, because they transcribe in opposing directions in the zebrafish (E) and in the same direction in humans (F).