One of the first and more interesting studies to tackle this question, made used of an unorthodox FXS mouse model: a mouse displaying mosaic expression of Fmr1 (as it is in FXS females), including a reporter gene (GFP), to allow discrimination between cells based on whether they express FMRP, or not (Hanson and Madison, 2007). Here, FMR1 is linked to fragile X syndrome.