title: Nail DNA and possible biomarkers: a pilot study.
abstract: OBJECTIVE
  Nail has been a substitute DNA source for genotyping. To investigate the integrity and consistency of nail DNA amplification for biomarker study, nail clippings from 12 subjects were collected at monthly intervals. The possibility of longer amplification and existence of GAPDH RNA/protein, were also investigated with three nail samples.
  
  
  METHODS
  Three primer sets were designed for quantitative amplification of nuclear and mitochondrial genes and analysis of their consistency. The mean threshold cycles in amplification of the target genes were compared to test the consistency of polymerase chain reaction (PCR) performance among individual factors including age groups, sex, family, the nail source, and by the size of the amplification segments.
  
  
  RESULTS
  The amplification of the target genes from nail DNA showed similar integrity and consistency between the nail sources, and among the serial collections. However, nail DNA from those in their forties showed earlier threshold cycles in amplification than those in their teens or seventies. Mitochondrial DNA (mtDNA) showed better DNA integrity and consistency in amplification of all three targets than did nuclear DNA (nucDNA). Over 9 kb of mtDNA was successfully amplified, and nested quantitative PCR showed reliable copy numbers (%) between the two loci. Reverse transcription PCR for mRNA and immunoblotting for GAPDH protein successfully reflected their corresponding amounts. Regarding the existence of RNA and protein in nails, more effective extraction and detection methods need to be set up to validate the feasibility in biomarker study.
  
  
  CONCLUSIONS
  Nail DNA might be a feasible intra-individual monitoring biomarker. Considering integrity and consistency in target amplification, mtDNA would be a better target for biomarker research than nucDNA.
authors.affiliation: Genetic Epidemiology Research Institute, University of California, Irvine, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Park
authors.forename: Debbie
authors.initials: D
authors.lastname: Liang
authors.forename: Jung Woo
authors.initials: JW
authors.lastname: Kim
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Luo
authors.forename: Taesheng
authors.initials: T
authors.lastname: Huang
authors.forename: Soo-Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Seong-Sil
authors.initials: SS
authors.lastname: Chang
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D015415:Biomarkers / Q000032:analysis; D002648:Child; D004247:DNA / Q000032:analysis* / Q000302:isolation & purification; D017931:DNA Primers; D004272:DNA, Mitochondrial / Q000032:analysis; D005240:Feasibility Studies; D005260:Female; D005784:Gene Amplification; D006801:Humans; D008297:Male; D008875:Middle Aged; D009262:Nails / Q000737:chemistry*; D010865:Pilot Projects
chemical_list: D015415:Biomarkers; D017931:DNA Primers; D004272:DNA, Mitochondrial; D004247:DNA