Friday, December 14, 2007

Dyslexic (Dyspraxic) Birds

What are the genetic basis of language? Mutations of the gene FOXP2 cause developmental verbal dyspraxia (DVD), a speech and language disorder that compromises the fluent production of words and the correct use and comprehension of grammar. But is FOXP2 role in audio communication a human innovation?

It seems not. Sebastian Haesler and collegues in Berlin have tried to suppress FOXP2 function in live zebra finchs , a cute Australian bird that is often used for study on learning. Male zebra finchs, in fact, learn their song from their parents.

The image above, from the Haesler paper, shows that the birds lacking FOXP2 function are much less accurate in imitating their parent's song. While the controls' spectrograms nearly perfectly match those of their tutors, FOXP2 defective birds struggle to imitate them but with evidently poor results. Most strikingly, the defects are similar to those of children born without a properly functional FOXP2 gene.

What does it mean? The neuromolecular basis of language are not a human innovation: they are shared by birds and humans. The same gene controls speech/song learning and production in both species nervous system. This means, amazingly, that the basis for speech-like audio communication were laid before the split between Synapsida (mammalians and extinct "mammalian-like" reptiles) and Sauropsida (other reptiles, including birds). It must have been some reptile-like amphibian in the moist forests of Carboniferous, more than 330 millions of years ago, to first emit the progenitor of both birdsongs and human songs.

Full open access paper on PLoS Biology, where you can also listen the normal and FOXP2-impaired zebra finch songs!

Sunday, December 9, 2007

Communicating with the enemy

Being a prey is always hard; being a toxic prey is somehow better, but you have to warn your enemies you are not a good deal. How do you do it? Toxic or otherwise harmful animals display colourful visual signals that mean "don't eat me, or you will regret it". Predators at first may not know the meaning of the signal, but after their first encounter, they will learn to avoid the colourful but toxic ones, and the other preys will be saved. But how did this kind of signaling evolve? Why some species evolve it, and some else not?

Analyzing the evolution of the caterpillars of the butterflies Papilio , Kathleen D. Prudic and coworkers discovered that the evolution of such signals is most influenced by the visual background on which the caterpillar preferibly is found. Caterpillars eating herbs or other narrow-leaved plants independently evolved warning signals for predators, while the ones eating on trees and other plants with large leafs did not. That is, warning signals evolve where there are consistent backgrounds that make it easier for the predator to recognize them and learn, while on complex environments like trees such visual clues could take a while to be recognized by predators, making the strategy inefficient.

Full open access article on PNAS

Monday, December 3, 2007

Earth-mass planets detected by 2011?

Good news everyone. The systemic blog reports exciting developments for exoplanets addicted (like me). New exoplanets detection rate is now as high as one planet per week. And there is more. If the extrapolation above holds, it means that we will be routinely detecting Earth-size planets around nearby stars by 2011-2012. I wonder when we will begin to detect moons of these critters.

Friday, November 30, 2007

The vaults resolved

What are vaults? These 50 nm-long hollow capsules are made of almost 100 proteins, plus RNA components, and rank among the largest supramolecular structures found in eukaryotic cells. Yet their function is still unknown. They could have a function in the immune system, in tumour drug resistance, or in nucleus-cytoplasm trafficking. There is also a practical reason for studying vaults. This kind of molecular spaceship could one day be engineered to carry pharmacological agents in the cells.

Characterize molecular complexes as gigantic as vaults is one of the most daunting tasks for science today. They lie in a "dark" length scale. Smaller molecules are easy often to crystallize and thus to get their structure solved atomically thanks to X ray diffraction. Larger structures can be characterized with microscopy. Vaults lie in the middle: too large to efficiently crystallize, too small to be solved with conventional microscopy. The three-dimensional general barrel shape of vaults has been structurally described by mean of cryo-TEM at low resolution. A hollow symmetric shell (able to encapsulate entire ribosomes), with two protrudring caps, was revealed, but that pretty was it.

Now, Daniel H. Anderson and others have resolved the structure of the vault shell protein at 0.9 nm resolution. The picture is still fuzzy compared to the atomic resolution of many protein crystal structures, but it is an enormous step forward compared to the previous structures. The vault can now be understood in terms of the assemby of the individual molecules that compose it. It is a beautiful, daunting mosaic of intertwined protein chains.

You can read the full paper on PLoS Biology.

Friday, November 2, 2007

An hydrogen eclipse

How do you catch a planet around another star? One of the most important techniques used is looking for transits -that is, the tiny dip in star brightness when a planet passes in front of the star itself. By studying such phenomena, a surprising number of informations can be squeezed out, for example on the remote planet atmosphere composition or temperature. Recently, researchers at the UCSC discovered something really odd about the gas giant HD 209458 b. They compared the transit depth (i.e. the amount of starlight blocked by the planet) in visible light and in the ultraviolet band that is absorbed by hydrogen -the Lyman-alpha line.

They did find that the transit is much deeper in the Lyman-alpha light, just like if the planet was much larger in that frequence (see image above). This means that HD 20958 b has a gigantic hydrogen comet-like cloud around it, that would be quite transparent for our sight but dramatically conspicuous in the ultraviolet.

Read the original story on the Systemic blog.

Monday, October 22, 2007


This is a NASA's Hubble Space Telescope color image of Ceres, the largest Main Belt asteroid and one of the three known dwarf planets of the Solar System. At 18 km/pixel, this is probably the best picture currently available of this world. Don't be fooled by the light appearance -the image is actually contrast-enhanced to show features, Ceres by itself absorbs 91% of light falling on it. The Dawn Mission is going to show us better pictures in 2015.

Saturday, October 20, 2007

An healthy mouse challenges genome evolution models.

Why is this mouse healthy? Scientists know that genomes of mammals share DNA sequences whose function is unknown, but that are perfectly conserved between species. It seems natural to think those sequences must be somehow vital to the organism, since tens of million years of evolution didn't touch them. Yet when they deleted one of them (herein printed under the mice) from the genome of some mice, they found that no apparent side effect happens. What is the role, then, of these sequences?

Read the full story on PLoS Biology.