For her elucidation of the genetic defects in hereditary deafness and other sensory disorders.

Who she is. Christine Petit is Professor of Genetics and Sensory Physiology at the Pasteur Institute, and Director of the Sensory Deficit Genetics Unit, INSERM, Paris. She is also Professor and Chair of Genetics and Cell Physiology at the Collège de France, Paris. Christine Petit trained in Paris both as a medical doctor and as a geneticist and biochemist. Her medical training was followed by six years in the immunochemistry laboratory at the Pasteur Institute before taking up a postdoctoral position in Basel, Switzerland. She then went back to France and worked at the CNRS molecular genetics centre in Gif-sur-Yvette, before returning to the Pasteur Institute in 1985.

In recognition of her research, Professor Petit has been the recipient of many awards, the most recent being the 2006 Louis-Jeantet Prize for medicine.  In 2002 she was named a Chevalier de l’Ordre de la Légion d’Honneur, one of the highest awards of the French state, for her contribution to science and, in the same year, was elected a member of the French Academy of Sciences.

What she does. Christine Petit is best known for her contribution to understanding the genetic basis of sensory disorders. Her work on hereditary deafness has benefited many affected families worldwide and brought the molecular bases of several developmental and functioning processes of cochlea, the auditory sensory organ, to light.

What that means. Deafness is the most frequent sensory defect, affecting about one child in eight hundred at birth and one in every five hundred before adulthood. Until now, the cause of deafness has been difficult to identify as it can be either hereditary or have an environmental cause such as infections or excessive noise.

Professor Petit was the first researcher to properly address the way to identify the genes involved in hereditary deafness in humans and to decipher their underlying cellular and molecular defective mechanisms. As deaf people tend to marry other deaf people, genetic linkage analysis, which is a prerequisite to isolate deafness genes, is particularly difficult. Christine Petit overcame this problem by studying geographically isolated families suffering from hereditary deafness in Tunisia, Morocco, Iran and Lebanon, thanks to collaborations with physicians and scientists from these countries. Indeed, such isolated families are usually founded by a small number of people, which makes it more likely that deaf family members are affected by the same gene defect.

Christine Petit pioneered the field of inherited deafness. She showed how to identify the genes involved in this sensory defect and isolated the genes underlying approximately 15 forms of deafness. She also demonstrated that, even though 100 different genes may cause congenital deafness, a single gene is responsible for about half congenital forms. As a result, congenital deafness, in developed countries, is now known to be of genetic origin in 80% of cases. Moreover, genetic counseling made available to families of deaf children has improved thanks to the development of molecular diagnosis. She clarified the underlying cellular and molecular mechanisms malfunctioning in several forms of deafness. In particular, together with her colleagues, she demonstrated that in Usher syndrome type I, a very severe disorder, combining deafness and blindness, each of the five causative genes known at present, code for proteins which interact in order to ensure the proper cohesion of the hair bundle, an ensemble of apical microvilli, crowning the auditory sensory cells and stimulated by sound.

Christine Petit’s work on the sensory system also led her to identify genes responsible for Kallman syndrome – the only hereditary human disease causing a loss of olfaction.

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