Monday, September 14, 2009


Aberrant overexpression of XTINK genes triggered the extinction of dinosaurs in late Cretaceous

T. Arzán, T. Rex, T. Existe and J. Weissmuller Jr.
Unidad de Extinción de Especies, Dinopolis Amusement Park, Teruel, Spain

Dinosaur massive extinction at the end of Cretaceous period is a favourite recurrent theme at educational institutions, Science museums, and story-telling colloquia (see, for instance, Jindetrés). The knowledge about the causes of dinosaur extinction moves from the absolute ignorance for most of the normal people to the catastrophic Geologist’s theory on the impact of an asteroid with the Earth crust a few millions years ago. In addition, a group of Biologists and Mathematicians defend as a reasonable hypothesis to explain this extinction the lethal unbalance between the short intelligence and the big size of most dinosaurs, when compared with the attributes of their smarter competitors, the archaic shrew-like mammals. Here, we have followed an un-biased molecular approach, based on the search for extinction-specific reptilian genes, to ascertain the genetic basis of dinosaur extinction. A comprehensive gene expression analysis was performed using mRNA samples from alive individuals from two current crocodilian species, American alligator (Alligator mississippiensis) and Nile crocodile (Crocodylus niloticus), in comparison with archival samples from African crocodile specimens that had been slaughtered during the filming of Tarzan movies, several decades ago, while fighting for survival against this famous wild hero. Blinded OJIMETRIXTM analysis of the microarray chips, followed by in situ toothpick-substractive hybridization, identified thirteen highly related genes, XTINK-1 to XTINK-13, which were aberrantly overexpressed in samples from extinct crocodile specimens, in comparison with samples from alive animals. XTINK-13 gene was the more frequently overexpressed gene in Tarzan’s movies crocodiles, and a good positive correlation (p<0.000001) was found between the XTINK-13 mRNA overexpression levels and the number of stabs that the crocodile received from Tarzan during the fight. Measurement of random, non-selective interspecies variation of XTINK genes, using the XMELT algorithm, indicated that XTINK gene family diverged from its nearest gene ancestor about 60 millions years ago, which fits quite well with the time of the Cretaceous-Tertiary extinction event. As expected, transgenic mice expressing XTINK-13 were not reproductively viable, and repeatedly died of unfortunate incidents, such as lack of water or food in the cage, intoxication during routine fumigation of the animal house, or lethal mishandling by non-trained technicians. As a matter of fact, the functional experiments with XTINK-13 had to be interrupted, after several PhD students working with this gene abandoned the laboratory as a consequence of the concatenation of sad events attributable to very bad luck, including continuous deep punctures with biologically contaminated needles, embarrassing slips on dry floor, painful head bumping against half-closed glass doors, and severe electric shocks caused by their computer keyboards. We conclude from our studies that XTINK genes possess extinction prone-like properties, and propose that extinction of some reptiles, including dinosaurs in the late Cretaceous, may have been the consequence of aberrant and inopportune overexpression of XTINK genes along evolution.

1 comment:

  1. Dear Arzán et al.; I feel very concerned about your findings. Have you thought about the military potential of the finding of these XTINK genes? Actually, their origin may have been an evolutionary trick to dismiss wrong or too dangerous species, as suggestedd by many story-telling colloquia that you mention (thanks for referencing our site!).

    If the C.I.A. contacts you, please take care of the ethic dilemma involving your publication.