SMN1 and proximal spinal muscular atrophy: Using our dataset from iPSC-MN differentiation studies we concur that the FL/Δ7-SMN mRNA ratio is a robust parameter to distinguish control individuals with two functional SMN1 alleles and SMA patients, as described in cell cultures, foetal tissues and adult whole blood samples10, 37, 64, but our results also indicate that it is not suitable to differentiate wild-type from the carrier mother.