FMR1 and fragile X syndrome: Sequencing of the cerebellum, periventricular white matter, and BA10 in FXS 5319, captured a range of full mutation variants with repeat sizes ranging from 300 – 387, 249 – 486, and 255 – 434, respectively (Fig. 2i–k) with the periventricular white matter containing the largest range of FMR1 alleles (Fig. 2l).