Scientific team reconstructs origins of Y chromosome in Atlantic herring Oaks

An international team of researchers led by Leif Andersson, a professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences, has been able to reconstruct the origins of the male sex chromosome in the Atlantic herring, determining that the male-specific region of this genetic storehouse contains only three genes: a sex-determining factor and two genes for sperm proteins.

This research provides further insight into how organisms develop into one sex or another and how the mechanisms for these developmental decisions are controlled genetically.

Chromosomes are structures of highly organized DNA that serve as one book in an organism’s biological library, or genome. Sex chromosomes specifically play an important role in determining whether an organism develops as male or female. The study of these structures is important as it allows us to understand the mechanism of sex-determination in development.

However, this research can be difficult as sex chromosomes degenerate quickly and have high rates of mutations. The Atlantic herring is unique in that both versions of its sex chromosomes (X and Y) are almost identical in gene content.

In a recent study published in the Proceedings of the National Academy of Sciences, Andersson and his colleagues, based at Uppsala University in Sweden, determined that the only difference between X and Y was that the Y chromosome, found only in males, has three additional genes: a sex-determining factor (BMPR1BBY) and two sperm protein genes predicted to be essential for male fertility.

By observing the structure of these three genes in the Y chromosome, the researchers were able to trace the molecular evolutionary path that led to the Atlantic herring’s current Y chromosome, reconstructing its birth in a piecewise fashion.

“This study is unique because we have been able to reconstruct the birth of a sex chromosome,” Andersson said. “Usually, sex chromosomes evolved a long time ago, like for human Y, and many changes have occurred that make it impossible to sort out the first critical steps. That is exactly what we have done in the herring.”

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