Pitx1 regulation ; syndromes associated with Gremlin and Shh genes

In this fourth lecture, a detailed analysis of PITX1 gene regulation is completed, providing the beginnings of an explanation of the molecular etiology of Liebenberg syndrome. Next, a patient showing oligosyndactyly and a deletion in the formin gene is discussed to illustrate the presence of enhancer sequences within introns of genes neighboring the target gene, a situation frequently encountered in long-distance regulation. In this particular case, we're talking about the Gremlin gene, whose transcription is controlled, among other things, by elements localized in the nearby formin gene. Finally, the prototypical long-distance regulation of the Shh gene is discussed, through both the Sasquatch insertion mutation in mice, and pre-axial polydactyly in patients.