Hagfish genome study reveals timing and impact of vertebrate genome duplications

An inshore hagfish genome study highlights two pivotal genome duplications in early vertebrates, with major morphological evolution following the second event. The study by Juan Pascual-Anaya, Daqi Yu and many others was published on April 10.

Whole genome duplications (WGDs) are considered influential in the evolution of organisms, according to the study. The widely recognized "2R Hypothesis" posits that two such duplications took place in the early stages of vertebrate evolution. While many concur that the first duplication transpired prior to the split of living vertebrates, the study states that the timing of the second remains disputed, especially concerning the split between jawless and jawed vertebrates.

Efforts to pinpoint the timing have been hindered due to limited genomes of cyclostomes, according to the study. Recent genome studies of sea lamprey and Arctic lamprey have yielded varying interpretations of this second duplication. The unveiling and analysis of the inshore hagfish's genome now offer fresh insights into these evolutionary events, the study stated.

Presenting the genetic data of the inshore hagfish, researchers embark on a journey of comparative exploration with genomes from lampreys and gnathostomes to trace the roots of jawless vertebrate genome evolution, according to the study. Through comprehensive genetic mapping and evolutionary lineage studies, evidence suggests the first duplication took place in early vertebrate lineage during the Cambrian period. The subsequent event is believed to have happened in the lineage, leading to jawed vertebrates after its split from their jawless counterparts. Interestingly, the research reveals not just one but two more independent duplications in the lineage, leading to jawless vertebrates. The study states that while WGDs are generally thought to drive developmental evolutionary changes consistently across vertebrate groups, observable physical evolutionary leaps seem to have manifested only after the second major duplication, challenging previously held notions about the impact of WGDs on morphological evolution.

Research Square: Juan Pascual-Anaya, et al., Hagfish genome illuminates vertebrate whole genome duplications and their evolutionary consequences, Biological Sciences (2023). https://doi.org/10.21203/rs.3.rs-2774434/v1