Deletions on chromosome 15 in the bands labeled 15q11.2-q13 on the chromosome inherited from a subject’s father cause Prader-Willi syndrome (PWS). The unique nature of this causative genetic event has been known for many years, but the precise manner in which it causes the developmental abnormalities of PWS is not completely understood since the region deleted removes many genes. We will capitalize on new techniques for growing human stem cells and manipulating their chromosomes to generate cell lines carrying the PWS deletion and compare them with genetically identical cells that do not carry the deletion. Using the CRISPR method for genome editing, we will generate precise cell models of PWS in which we can use high-throughput molecular analysis to examine the level of expression of all genes, both in the normal state and when the cells carry the PWS deletion. Importantly, we will be able to do this after differentiating the stem cells to neurons characteristic of the hypothalamus region of the brain, a region thought to be critically important to generating abnormalities characteristic of PWS subjects. By defining the changes in gene expression and cell behavior caused by the PWS deletion, we will then be able to use CRISPR to individually inactivate each candidate gene in the PWS region, testing in each case whether it is responsible for causing the differences that we detect to be characteristic of PWS. The results of these studies will provide a valuable new, genetically precise, human cellular model system for investigators in the field and will point to one or more specific gene(s) as responsible for the abnormalities of PWS. Importantly, they will also provide us a way to test whether it is possible to correct the changes caused by the PWS deletion by activating expression of the corresponding genes on the chromosome 15 inherited from the mother, which otherwise are present but remain silent.
Michael Talkowski, PhD
Massachusetts General Hospital