Limb anomalies in humans, Pitx1 and Liebenberg syndrome

In this third lesson, after a review of the mechanisms of growth and specification of the three axes of polarities of limb buds, the notions of " sequence enhancer " and " pleiotropy " are discussed, based on the case study of the three-spined stickleback. Then, after a few remarks on the prevalence of congenital limb malformations in Europe and their classifications, Liebenberg syndrome is presented - a malformation of the arms that, in many respects, resembles legs - and the reasons associating it with the PITX1 gene. A possible explanation of its molecular etiology is then proposed, leading to a detailed analysis of the complex regulation of this gene in mice. These experiments make use of recent chromatin analysis technologies, which are briefly introduced before moving on to the study of this genetic locus.