DNA was isolated from maternal blood (28 weeks’ gestation) and cord blood samples by Qiagen
DNA Blood Mini kit (Qiagen, Hilden, Germany) and diluted to 4 ng/μL. As previously described (Xu et al. 2017 (
link)), mtDNAcn and single copy hemoglobin beta (
HBB) gene were measured based on real-time quantitative polymerase chain reaction (PCR) and SYBR Green technology. In short, master mixes for mtDNA copy number and
HBB were prepared with
KAPA SYBR FAST qPCR Kit Master Mix (2X) ABI Prism (Kapa Biosystems, Woburn, MA, USA) and corresponding primers reported by Hou et al (Hou et al. 2010 (
link)). A real-time PCR machine (7900HT, Applied Biosystems, Foster City, CA, USA) was used to perform PCR and each run included a standard curve, a control sample and a blank. For the standard curve, one reference DNA sample (from three persons) was diluted to 5 concentrations: 1, 2, 4, 8 and 16 ng/μL, The control sample was to monitor the variance between runs, and the coefficient of variation (CV) of the control sample was 5.3% based on 16 runs. All samples and standard curve points were run in triplicates. R
2 for each standard curve was >0.99. The relative mtDNAcn (RmtDNAcn) was calculated by
SDS 2.4.1 software (Life Technologies) and indicates average mtDNAcn in each cell.
Xu Y., Wahlberg K., Love T.M., Watson G.E., Yeates A.J., Mulhern M.S., McSorley E.M., Strain J., Davidson P.W., Shamlaye C.F., Rand M.D., Myers G., van Wijngaarden E, & Broberg K. (2019). Associations of blood mercury and fatty acid concentrations with blood mitochondrial DNA copy number in the Seychelles Child Development Nutrition Study. Environment international, 124, 278-283.