2.4 Sample preparation
The heel blood of the neonatal subjects was collected into a special
filter paper, dry naturally at room temperature to form dried blood
spots (DBS). After conventional NBS, the DBS was stored at 4 ℃. Genomic
DNA was extracted from DBS using
QIAamp DNA Mini Kit (Qiagen, German) according to the operation manual.
Briefly, a punched-out circle from a DBS was placed into a 1.5 ml
microtube with Buffer ATL to dissolve DNA and incubated at 85°C for 10
min. Protein K was added to digest proteins. After 70°C-incubation and
adding ethanol, the buffer was transferred into a Mini spin column.
Finally, the DNA solution was eluted with Elution buffer after a series
of centrifugation. The quality and quantity of the DNA were assessed by
Qubit® 3.0 Fluorometer (Thermo Fisher Scientific Inc., USA) according to
the instruction.