Super-Mendelian inheritance mediated by CRISPR–Cas9 in the female mouse germline

A gene drive biases the transmission of one of the two copies of a gene such that it is inherited more frequently than by random segregation. Highly efficient gene drive systems have recently been developed in insects, which leverage the sequence-targeted DNA cleavage activity of CRISPR–Cas9 and endogenous homology-directed repair mechanisms to convert heterozygous genotypes to homozygosity1,2,3,4. If implemented in laboratory rodents, similar systems would enable the rapid assembly of currently impractical genotypes that involve multiple homozygous genes (for example, to model multigenic human diseases).

To our knowledge, however, such a system has not yet been demonstrated in mammals. Here we use an active genetic element that encodes a guide RNA, which is embedded in the mouse tyrosinase (Tyr) gene, to evaluate whether targeted gene conversion can occur when CRISPR–Cas9 is active in the early embryo or in the developing germline. Although Cas9 efficiently induces double-stranded DNA breaks in the early embryo and male germline, these breaks are not corrected by homology-directed repair. By contrast, Cas9 expression limited to the female germline induces double-stranded breaks that are corrected by homology-directed repair, which copies the active genetic element from the donor to the receiver chromosome and increases its rate of inheritance in the next generation.

These results demonstrate the feasibility of CRISPR–Cas9-mediated systems that bias inheritance of desired alleles in mice and that have the potential to transform the use of rodent models in basic and biomedical research.

Tesco counter cost cuts to hit 9,000 jobs

Tesco has announced it will close food counters in 90 of its stores as part of a wider cost-cutting plan that will affect 9,000 staff.

The UK's largest supermarket said its remaining fish, meat and deli counters in 700 stores will be run on a full-time or flexible basis.

It confirmed it will no longer offer a hot food service at its canteens and that head office staff will be cut.

It said up to 9,000 workers will be affected but half could be redeployed.

More than 10,000 jobs have been cut at Tesco since the current chief executive, Dave Lewis, took over in 2014.

The UK's biggest grocer is in the midst of trying to save £1.5bn as the competition between supermarkets intensifies.

Seoul

Lake Titicaca

Panda in Toronto Zoo

On the Beach. Soviet Ukraine

Niagara Falls at Winter Time

Glacier

Celebrating the 20th year of independence in Turkmenistan

Fazl Mosque in London

Punjab features mountainous terrain near the hill station of Murree

Saint Fin Barre's Cathedral, Cork

Chanel on the Solovki Islands

Leeuwarden_Panorama

Très Riches Heures du Duc de Berry or The Very Rich Hours of the Duke of Berry. 1410s

Zvenigorod Monastery, Moscow Oblast

Old Mostar from Minaret