Cell‐free fetal DNA tests for trisomy show promise in women at lower risk of affected pregnancies

delay silencing of the FMR1 gene and make prenatal screening for FMR1 mutations worthwhile. Findings of his study might be applicable to other diseases that arise from repeat nucleotide sequence expansions, such as types of Huntington disease, or amyotrophic lateral sclerosis, also called Lou Gehrig’s disease, as well as certain ataxias and other diseases found to result from an mRNA-DNA duplex, adds Dr. Hagerman. Even in blocking, if methylation would not cure FXS—as in cases where gene silencing does not occur despite an unmethylated full mutation, in which the enzymes that normally attach carbon and hydrogen bundles to DNA are not expressed—these findings may be useful because these patients still have low FMRP levels and are at risk for neurological problems, Dr. Hagerman notes. Many questions remain, including why FMR1 works and expresses FMRP only temporarily. “There’s still no idea of how . . . it [FMRP] is expressed and then [production] suddenly shuts down. What changes?” says Dr. Budimirovic. He suggests research is needed with FXSand patient-specific hESC to make sure the mechanism identified by Dr. Jaffrey’s team is how FXS arises in affected families because different sets of mutations tend to be inherited together.