New Look on an Old Experiment

(November 29th, 2016) Ill-reputed Austrian 19th century biologist, Paul Kammerer, receives scientific support from current colleagues. They came up with a model of possible epigenetic mechanisms for Kammerer's midwife toad experiments. 





Filled with the infinite sadness of an irreversibly broken reputation, Paul Kammerer walked into the Austrian Schneeberg Forest - his head deep in thought. He had been so close to starting a new institute of experimental biology in Moscow, so close to convincing the love of his life to follow him to Russia. But one short letter to Nature on August 7th, 1926, signed by Dr. G. K. Noble, curator of reptiles at the American Museum of Natural History, branded him a cheat and sealed his doom. He thought of Jean Baptiste Lamarck, who described how traits acquired by the parents can be passed down to the next generation. According to Lamarck, giraffes had long necks because an ancestral giraffe had stretched its neck a little and passed that character to its descendants. These ideas earned Lamarck many adversaries before he went blind and died in 1829. 

Kammerer tried to focus on the good days before the Great War. At night, he was a musician in the Austro-Hungarian Empire. By day, he enthusiastically tested Lamarck’s ideas. He had found a perfect system for this purpose: the midwife toad. An amphibian that normally mates on land but Kammerer forced it to reproduce in water, by putting the toads in a heated environment with a pond. Kammerer eventually realised that the challenging experience of the parents modified their offspring. They now preferred to mate and breed in water. 

Within a few generations, the toads even developed “nuptial pads” on their fingers to be able to grab the female toad, while copulating underwater. He was so happy that he kissed the toads and then proceeded to cross them. To his surprise, the progenies followed Mendelian rules. Kammerer considered that the environmental challenge created new genes that segregated according to Mendel’s laws. Other characters, such as body size, did not show these trends. Desperately, he sought for an idea to explain his results. But after World War I, Austria was devastated and his preserved specimens lost. Except for the one that Noble used to dismiss the nuptial pads as forgery, as deliberately-made stains of India ink on the toad’s fingers.  

The idea sought after desperately by Kammerer was epigenetics. Only now, almost one hundred years later, have Alexander Vargas (University of Chile), Quirin Krabichler (Technical University of Munich) and Carlos Guerrero-Bosagna (Linköping University) come up with a simple epigenetic model that could explain Kammerer’s results. According to Vargas et al., Kammerer could have triggered an epigenetic mark on the toads' DNA. By forcing the toads to mate underwater, he exposed toad embryos to a different environment from the one their parents experienced, during their embryonal development. Vargas et al. propose that this changed environment resulted in DNA methylation, which could switch on and off genes required for mating. Once such an epigenetic mark is on the chromosomes, it will be maintained in the next generations, even if the original stimulus ceases. Kammerer reported precisely that the toads continued to prefer water in successive generations, even if their environment was no longer heated. 

After 90 years, it is clear that Kammerer was a pacifist in a world of wars, a Jew in a growing anti-Semitic Europe, a communist-friendly musician in a laboratory of biology and, above all, a neo-Lamarckian in a time obsessed with Mendel, Darwin and eugenics. It is unclear why we have called him a fraud for so long, given that no one has tried seriously to reproduce his work. 

Nowadays, as Vargas et al. suggest, we could repeat the experiments and look for epigenetic marks in the toad genome, triggered by the conditions Kammerer used. Only then could we know whether the man, who tragically committed suicide in the Schneeberg Forest on September 23rd 1926, is actually the father of epigenetics. 


Alejandrolvido

Image: George Grantham Bain Collection (Library of Congress)




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