PT  - JOURNAL ARTICLE
AU  - Yuan Mu
AU  - Xin Huang
AU  - Rui Liu
AU  - Yulin Gai
AU  - Na Liang
AU  - Daiqing Yin
AU  - Lei Shan
AU  - Shixia Xu
AU  - Guang Yang
TI  - <em>ACPT</em> gene is inactivated in mammalian lineages that lack enamel and teeth
AID  - 10.1101/861633
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 861633
4099  - http://biorxiv.org/content/early/2019/12/02/861633.short
4100  - http://biorxiv.org/content/early/2019/12/02/861633.full
AB  - Loss of tooth or enamel is widespread in multiple mammal lineages. Although several studies have been reported, the evolutionary mechanisms of tooth / enamel loss are still unclear. Most previous studies have found that some tooth-related genes have been inactivated in toothless and / or enamel-less mammals, such as ENAM, ODAM, C4orf26, AMBN, AMTN, DSPP, etc. Here, we conducted evolutionary analyses on ACPT plays a key role in amelogenesis, to interrogate the mechanisms. We obtained the ACPT sequences from 116 species, including edentulous and enamel-less mammals, then evolutionary analyses were implemented. The results showed that variant ORF-disrupting mutations have been detected in ACPT coding region among nine edentulous baleen whales and three enamel-less taxa (pygmy sperm whale, aardvark, nine-banded armadillo). Furtherly, selective pressure uncovered that the selective constraints have been relaxed among all toothless and enamel-less lineages. Moreover, our results support the hypothesis that mineralized teeth were lost or degenerated in the common ancestor of crown Mysticeti through two shared single-base sites deletion in exon 4 and 5 of ACPT among all living baleen whales. DN / dS values on transitional branches were used to estimate ACPT inactivation times. In the case of aardvark, inactivation of ACPT was estimated at ~23.60-28.32 Ma, which is earlier than the oldest pangolin fossil time (Orycteropus minutus, ~19Ma), suggesting that ACPT inactivation may result in degeneration or loss of enamel. Conversely, the inactivation time of ACPT estimated in armadillo (~10.18-11.30 Ma) is later than the oldest fossil time, suggesting that inactivation of ACPT may result from degeneration or loss of enamel in these mammals. Our findings suggested that different mechanisms of degeneration of tooth / enamel might exist among toothless and enamel-less lineages during evolution. Our study further considered that ACPT is a novel gene for studying tooth evolution.ACPTAcid Phosphatase, TesticularEMPenamel matrix proteinPAMLphylogenetic analysis by maximum likelihoodPPposterior probabilityMamillion years ago