Friday, April 12, 2024

Genetics solves mystery of rare brown pandas after 40 years

Despite being relatively bad at surviving on their own, Pandas are popularly regarded as cuddly, endearing animals of the animal kingdom. While they’re known for their unique markings, did you know that not all of them are black-and-white?

Indeed, there are brown-and-white pandas, which rank among the most striking creatures one may encounter. These brown-and-white giant pandas are distinct coat color mutants found exclusively in the Qinling Mountains of China. 

Since the first brown panda was found in 1985, eleven records have been reported by official news or personal communications, of which seven cases have been confirmed with photographs or entities: three from Foping County, two from Yangxian, one from Taibai, and one from Zhouzhi. All brown pandas were found exclusively in the Qinling Mountains, indicating that they are endemic to this region.

According to new research published by the Proceedings of the National Academy of Sciences, the reason for this color wave of pandas has finally been uncovered – and it’s all to do with a missing sequence of DNA. “Coat color variation has substantial adaptive and cultural value in mammals,” said study’s first author Dr. Dengfeng Guan from the Key Laboratory of Animal Ecology and Conservation Biology at the Chinese Academy of Sciences and colleagues. “This trait is directly determined by the ratio of eumelanin to pheomelanin, as well as the density and distribution of melanosomes in hair.”

“These factors are under complex regulation by hundreds of genes that influence various aspects of melanogenesis, including melanocyte proliferation and migration, melanin synthesis, and melanosome biogenesis and transfer.”

Dr. Guan and colleagues conducted a study involving two family trios linked to the brown panda Qi Zai, sequencing their genomes. They also examined ecological and genetic data collected from their extensive research on wild giant pandas in the Foping Nature Reserve. Additionally, they investigated the cellular mechanisms responsible for the brown coat color through microscopy and transmission electron microscopy analysis.

They identified the candidate mutation, a 25-bp deletion in Bace2 gene, as the most likely genetic basis of brown pandas.They validated this deletion through sequencing of an additional cohort of 192 black pandas and CRISPR-Cas9 knockout mice.

This investigation revealed that this mutation reduced the number and size of melanosomes of the hairs in knockout mice and possibly in the brown panda, further leading to the hypopigmentation. These findings provide unique insights into the genetic basis of coat color variation in wild animals, and could also guide scientific breeding of the rare brown pandas.


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