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This Week in PNAS: May 26, 2009

In work published in the early online edition of PNAS this week, scientists study how evolutionary selection affects modes of gene regulation. Using a model that takes into account genetic drift, mutation, and time-dependent selection, they found the "effective population size and the typical time scale of environmental variations to be key parameters determining the fitness advantage of the different modes of regulation," they say in the abstract.

A study led by Hey-Joo Kang at the Center for Reproductive Medicine and Infertility of Weill Cornell Medical College has found SNPs in the p53 pathway that regulate fertility. After making a list of SNPs in the p53 pathway that can modify the function of p53, they found several genes to be enriched among IVF patients, including the p53 allele encoding proline at codon 72 and several alleles in the LIF, Mdm2, Mdm4, and Hausp genes. "The association of SNPs in the p53 pathway with human fertility suggests that p53 regulates the efficiency of human reproduction," they say.

Research led by David Baker has used computational analysis to study enzyme specificity. In this paper, his team describes a computational method for "introducing specific enzyme-substrate interactions by directed remodeling of loops near the active site." Testing it on eight native protein-ligand complexes showed that the method "can recover native loop lengths and, often, native loop conformations," they write.

Scientists at the Russian Academy of Sciences have designed an antireceptor antibody-photosensitizer fusion protein to target cancer cells. Their "fully genetically encoded immunophotosensitizer" is comprised of a specific anti-p185HER-2-ECD antibody fragment 4D5scFv fused with the fluorescent protein KillerRed. They write that both parts of the recombinant protein were functional, showing high affinity and light activation of sensitizer and that 4D5scFv-KillerRed "efficiently killed p185HER-2-ECD-expressing cancer cells upon light irradiation," they say.

The Scan

Pig Organ Transplants Considered

The Wall Street Journal reports that the US Food and Drug Administration may soon allow clinical trials that involve transplanting pig organs into humans.

'Poo-Bank' Proposal

Harvard Medical School researchers suggest people should bank stool samples when they are young to transplant when they later develop age-related diseases.

Spurred to Develop Again

New Scientist reports that researchers may have uncovered why about 60 percent of in vitro fertilization embryos stop developing.

Science Papers Examine Breast Milk Cell Populations, Cerebral Cortex Cellular Diversity, Micronesia Population History

In Science this week: unique cell populations found within breast milk, 100 transcriptionally distinct cell populations uncovered in the cerebral cortex, and more.