Genetics & Molecular Biology

Some chickens appear to be male on one side of the body and female on the other, and researchers writing in Nature this week say they know why.

It was previously thought that sex chromosomes in birds control whether a testis or ovary forms, with sexual traits then being determined by hormones.

The authors of the new study, however, identified differences between male and female cells that control the development of sexual traits. The scientists have named the phenomenon, cell autonomous sex identity (CASI).

The findings may also be relevant to why males and females differ in behavior and in susceptibility to disease.
Sonic hedgehog, a gene that plays a crucial rule in the positioning and growth of limbs, fingers and toes, has been found in the ectoderm - the cell layer that gives rise to the skin - in the embryos of developing mice. The gene was previously thought to be exclusively present in the cell layer that builds bone and muscle, called the mesoderm.

The discovery, detailed in PNAS, suggests that Sonic hedgehog's role in the growth of appendages is far more complex than originally thought. Developmental biologists may have to rethink established theories about how limbs are patterned in vertebrates — an effort that could provide insight into human birth defects.
A team of Georgia Institute of Technology scientists are reporting that molecules they term "unselfish" may have midwifed the birth of life's original (sometimes called "selfish") genes. The Georgia Tech scientists are investigating the possibility that intercalator molecules such as ethidium could have assisted life's non-living building blocks in forming complex organic chains and might have entered into the selection of DNA double helix base pairs.
This is the second in a present series, highlighting a particular incidence of  discrimination here and now, and those new to this may consider my intent to do some wider campaigning around this issue so here is a summary of what has happened since the first in this series was originally blogged.
Researchers writing in Nature say they have developed a new strategy to identify and characterize genes involved in endocytosis - the process cells use to ingest substances from the external environment. From their findings the scientists say they may be able to develop treatments for serious disease like cancer, Huntington’s and diabetes.

Cells take up material from the outside by pinching off from their cell membrane vesicles that transport substances to different cellular organelles. Depending on what they contain, these vesicles and organelles – also known as endosomes – are transported to different locations within the cell, where their content is either re-distributed or broken down to recycle the basic building blocks.
A team of researchers has demonstrated for the first time the specific activity of the protein NEIL3, one of a group responsible for maintaining the integrity of DNA in humans and other mammals. The discovery is detailed in the Proceedings of the National Academy of Sciences.

Since it first was identified about eight years ago, NEIL3 has been believed to be a basic DNA-maintenance enzyme of a type called a glycosylase. These proteins patrol the long, twisted strands of DNA looking for lesions—places where one of the four DNA bases has been damaged by radiation or chemical activity.
Preventing mosquitoes from urinating as they feed on blood could prevent the spread of dengue fever, yellow fever and other diseases, say researchers writing in the American Journal of Physiology.

When mosquitoes consume and process blood meals, they must urinate to prevent fluid and salt overloads that can kill them. The research team found that blocking a protein in the renal tubules of Aedes aegypti mosquitoes prevents them from relieving themselves. The work may lead to the development of new insecticides to disrupt the mosquito's renal system, which contributes to a mosquito's survival after feeding on blood.
Modern humans are generally monogamous while exhibiting tendencies toward polygamy over the course of evolutionary history, say scientists who analyzed genomic data from three population samples of African, Asian and European origin. The findings, published in the American Journal of Human Genetics, are consistent with studies in evolutionary psychology and anthropology that depict contemporary human populations.
Scientists writing in the FASEB Journal say a genetically modified strain of tobacco can help temper the damaging effects of toxic pond scum, known as microcystin-LR (MC-LR), which makes water unsafe for drinking, swimming, or fishing. The plant could serve as a major tool for helping keep water sources safe to use, especially in developing nations.

The new strain was developed by inserting genes which code for the production of an antibody called MC-LR. With the genes in place, the new strain of tobacco produced the antibody in its leaves and secreted it from its roots into the surrounding hypotonic growth medium.
Why do some people who experience traumatizing events develop Post-Traumatic Stress Disorder while others don't? Scientists know that, in general, the more traumatic events a person experiences the higher their likelihood of developing PTSD, but even under extreme stress not all individuals develop the disorder. Now, researchers writing in Biological Psychiatry say that survivors of the 1994 Rwandan Genocide may help explain how genetic factors influence this relationship.