Scientists Sequence Octopus Genome

An international team of scientists has sequenced and annotated the genome of the common California two-spot octopus (Octopus bimaculoides), the first cephalopod to be fully sequenced. They discovered striking differences between the genomes of the octopus and other invertebrates. Hundreds of genes specific to octopus were identified, with many highly expressed in structures such as the brain, skin, and suckers.

The team estimates the O. bimaculoides genome is 2.7 billion base-pairs in size, with numerous long stretches of repeated sequences. They identified more than 33,000 protein-coding genes, and placed the octopus genome as slightly smaller than the human genome, but with more genes.

The team also suggests that the most notable gene expansion in the octopus was in the protocadherins, a family of genes that regulate neuronal development and short-range interactions between neurons. The octopus genome contains 168 protocadherin genes—10 times more than other invertebrates and more than twice as many as mammals. They also found that the octopus genome is enriched in transposons, also known as jumping genes. While their role in octopuses is unclear, the team found elevated transposon expression in neural tissues.

The sequencing project was conducted by teams from the University of Chicago, University of California, Berkeley, and Okinawa Institute of Science and Technology as part of the Cephalopod Sequencing Consortium. For more information, read the news releases at the University of California Berkeley website and at the University of Chicago website.