In a first, a team of researchers has successfully replaced both Y chromosomes in mice by increasing expression of just two genes while preserving the male's ability to produce offspring.
The findings show that live mouse progeny can be generated with assisted reproduction using germ cells from males which do not have any Y chromosome genes.
This discovery adds a new light to discussions on Y chromosome gene function and evolution and supports the hypothesis that Y chromosome genes can be replaced by that encoded on other chromosomes.
In the paper published online in the journal Science, a University of Hawaii (UH) team led by professor Monika A Ward described that only two genes of the Y chromosome were needed for male mice to sire offspring with assisted fertilisation.
With a collaborating researcher from France Michael Mitchell of INSERM, Marseille, Ward produced males completely devoid of the entire Y chromosome.
The offspring derived from the "No Y" males were healthy and lived for normal life span.
The daughters and grandsons of the "No Y" males were fertile and capable of reproducing on its own without further technological intervention.
Ward's team produced three consecutive generations of "No Y" males, showing that males lacking Y chromosome genes can be repeatedly propagated with technical assistance.
"Most of the mouse Y chromosome genes are necessary for development of mature sperm and normal fertilisation, both in mice and in humans," Ward noted.
"However, when it comes to assisted reproduction, we have now shown that in the mouse the Y chromosome contribution is not necessary," the authors added.
It suggests that there are back-up strategies within genomes which are normally silent but are capable of taking over under certain circumstances.
