PT  - JOURNAL ARTICLE
AU  - Pin Huan
AU  - Qian Wang
AU  - Sujian Tan
AU  - Baozhong Liu
TI  - Dorsoventral dissociation of Hox gene expression underpins the diversification of molluscs
AID  - 10.1101/603092
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 603092
4099  - http://biorxiv.org/content/early/2019/04/09/603092.short
4100  - http://biorxiv.org/content/early/2019/04/09/603092.full
AB  - Unlike the Hox genes in arthropods and vertebrates, those in molluscs show diverse expression patterns and, with some exceptions, have generally been described as lacking the canonical staggered pattern along the anterior-posterior (AP) axis. This difference is unexpected given that almost all molluscs share highly conserved early development. Here, we show that molluscan Hox expression can undergo dynamic changes, which may explain why previous research observed different expression patterns. Moreover, we reveal that a key character of molluscan Hox expression is that the dorsal and ventral expression is dissociated. We then deduce a generalized molluscan Hox expression model, including conserved staggered Hox expression in the neuroectoderm on the ventral side and lineage-specific dorsal expression that strongly correlates with shell formation. This generalized model clarifies a long-standing debate over whether molluscs possess staggered Hox expression and it can be used to explain the diversification of molluscs. In this scenario, the dorsoventral dissociation of Hox expression allows lineage-specific dorsal and ventral patterning in different clades, which may have permitted the evolution of diverse body plans in different molluscan clades.