An international team of scientists has produced a reference-quality, long-read-based genome assembly for the blue whale (Balaenoptera musculus).
The blue whale (Balaenoptera musculus). Image credit: NOAA.
The blue whale is one of the largest animals to have ever existed — an adult can reach up to 33 m (110 feet) and weigh 150 metric tons.
Genomic studies of giant animals are of interest to several subfields of biomedical science.
Understanding developmental mechanisms that control body size may have applications in regenerative medicine and animal husbandry.
Large mammals tend to have long lives and have developed mechanisms that make them resistant to cancer, in spite of having orders of magnitude more cells — and thus more cell divisions. This puzzling phenomenon is known as Peto’s Paradox.
“The genome is a blueprint of an organism,” said Dr. Yury Bukhman, a computational biologist at the Morgridge Institute.
“In order to manipulate cell cultures or measure things like gene expression, you need to know the genome of the species — it makes more research possible.”
“It’s generally understood that larger organisms take longer to develop from a fertilized egg to a full-grown adult than smaller creatures, but the reason why remains unknown.”
“It’s important just for fundamental biological knowledge from that perspective. How do you build such a large animal? How can it function?”
“A practical application of this knowledge is in the emerging area of stem cell-based therapies,” he said.
“To heal an injury, stem cells must differentiate into specialized cell types of the relevant organ or tissue.”
“The speed of this process is controlled by some of the same molecular mechanisms that underlie the developmental clock.”
In their research, the authors analyzed segmental duplications, large regions of duplicated sequences that often contain genes and can provide insight into evolutionary processes when compared to other species, either closely or distantly related.
They found that the blue whale had a large burst of segmental duplications in the recent past, with larger numbers of copies than the bottlenose dolphin (Tursiops truncatus) and the vaquita (Phocoena sinus), the world’s smallest cetacean.
While most of the copies of genes created this way are likely non-functional, or their function is still unknown, they did identify several known genes.
One encodes the protein metallothionein, which is known to bind heavy metals and sequester their toxicity — a useful mechanism for large animals that accumulate heavy metals while living in the ocean.
A reference genome is also useful for species conservation. The blue whale was hunted almost to extinction in the first half of the 20th century. It is now protected by an international treaty and the populations are recovering.
“In the world’s oceans, the blue whale is basically everywhere except for the high Arctic,” Dr. Bukhman said.
“So, if you have a reference genome, then you can make comparisons and can better understand the population structure of the different blue whale groups in different parts of the globe.”
“The blue whale genome is highly heterozygous, there’s still a lot of genetic diversity, which has important implications for conservation.”
The results appear in the journal Molecular Biology and Evolution.
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Yury V. Bukhman et al. 2024. A High-Quality Blue Whale Genome, Segmental Duplications, and Historical Demography. Molecular Biology and Evolution 41 (3): msae036; doi: 10.1093/molbev/msae036
