Part of the tectonic-like complex which is required for tissue-specific ciliogenesis and may regulate ciliary membrane composition. Part of the tectonic-like complex (also named B9 complex). Interacts with TMEM107. Localizes at the transition zone, a region between the basal body and the ciliary axoneme. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. TMEM138 and TMEM216 genes are adjacent and are aligned in a head-to-tail configuration. They share some cis regulatory region and display coordinated expression. Genes were joined by chromosomal rearrangement at the amphiboan to reptile evolutionary transition around 340 million years ago (PubMed:22282472).