Testicle

Bacteria genes offer new strategy for sterilizing mosquitoes

wolbachia bacteria
STERILITY CULPRITS Wolbachia bacteria (red) effectively sterilize a male mosquito by infecting the insect’s testes (blue), shown at 100 times magnification. Now, researchers have identified genes that may be responsible for the sterility.

A pair of bacterial genes may enable genetic engineering strategies for curbing populations of virus-transmitting mosquitoes.

Bacteria that make the insects effectively sterile have been used to reduce mosquito populations. Now, two research teams have identified genes in those bacteria that may be responsible for the sterility, the groups report online February 27 in Nature and Nature Microbiology.

“I think it’s a great advance,” says Scott O’Neill, a biologist with the Institute of Vector-Borne Disease at Monash University in Melbourne, Australia. People have been trying for years to understand how the bacteria manipulate insects, he says.

Wolbachia bacteria “sterilize” male mosquitoes through a mechanism called cytoplasmic incompatibility, which affects sperm and eggs. When an infected male breeds with an uninfected female, his modified sperm kill the eggs after fertilization. When he mates with a likewise infected female, however, her eggs remove the sperm modification and develop normally.

Researchers from Vanderbilt University in Nashville pinpointed a pair of genes, called cifA and cifB, connected to the sterility mechanism of Wolbachia. The genes are located not in the DNA of the bacterium itself, but in a virus embedded in its chromosome.

When the researchers took two genes from the Wolbachia

Human genes often best Neandertal ones in brain, testes

Neandertal brain
BRAIN ACTIVITY Human versions of some genes are more active in certain parts of the brain than Neandertal versions. Side and back views of a brain show that activity levels of the Neandertal version of a gene called NTRK2 are lower in the cerebellum (blue area in lower back) than in other regions.

Humans and Neandertals are still in an evolutionary contest, a new study suggests.

Geneticist Joshua Akey of the University of Washington in Seattle and colleagues examined gene activity of more than 700 genes in which at least one person carried a human and a Neandertal version of the gene. Human versions of some genes are more active than Neandertal versions, especially in the…