title: Estimation of size of clonal unit for keratinocytes in normal human skin.
abstract: OBJECTIVE
  It has been suggested that keratinocyte (KC) stem cells reside at the epicenter of a clonal population of cells. To estimate the territory or surface area covered by a single stem-cell-derived KC population in human skin, clonal skin maps were created from 3 healthy adult women and from normal skin of a psoriatic patient.
  
  
  METHODS
  Two hundred fifty-eight punch biopsy samples of various sizes (ranging from 2 to 8 mm in diameter) were analyzed for clonality employing X chromosome inactivation patterns at the human androgen receptor gene (HUMARA) locus. DNA was isolated and clonality established by significant decrease of either maternal or paternal X chromosome band patterns following restriction enzyme digestion, polymerase chain reaction amplification, and gel electrophoresis.
  
  
  RESULTS
  Fifty-three (41%) of 128 two-mm biopsies were clonal, whereas only 6 (14%) of 43 three-mm, 5 (14%) of 36 four-mm, and 3 (8%) of 35 five-mm biopsies revealed a clonal population of KCs. By contrast, in 5 different biopsies from a psoriatic patient, including 4- or 5-mm sizes, all but 1 were clonal; even an 8-mm biopsy contained a clonal population of KCs. Mantel-Haenszel chi(2) analysis revealed a P value of.001, reflecting a strong trend in probability for presence of a single clone of KCs as related to size of the biopsy sample. By sequentially analyzing 30 contiguous 2-mm biopsy samples within a given strip of skin, 10 clonal domain changes, as reflected in maternal versus paternal switches, were observed.
  
  
  CONCLUSIONS
  These results provide direct evidence of a clonal population of KCs in normal and psoriatic lesion-free skin, and indicate that a clonal epidermal unit of KCs frequently can be detected in small biopsies (2 mm), but that in normal skin sampling, overlapping clones are apparently present in larger (ie, 4-5-mm) biopsies, producing nonclonal patterns. The clonal domain of progeny in normal skin has a rather limited territorial boundary (2 mm in diameter). However, in lesion-free skin from a psoriatic patient, there may be clonal expansion of KCs due to perturbation in epidermopoiesis and/or stem cell distribution.
authors.affiliation: Department of Pathology, Loyola University Medical Center, Maywood, IL, USA.
authors.forename: Vijaya
authors.initials: V
authors.lastname: Chaturvedi
authors.forename: Sue
authors.initials: S
authors.lastname: Chu MD
authors.forename: Mathew
authors.initials: M
authors.lastname: Carrol BS
authors.forename: Jennifer W
authors.initials: JW
authors.lastname: Brenner BS
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Nickoloff
mesh_terms: D002999:Clone Cells; D004247:DNA / Q000032:analysis; D004303:Dosage Compensation, Genetic; D005260:Female; D006801:Humans; D015603:Keratinocytes / Q000166:cytology* / Q000473:pathology; D016133:Polymerase Chain Reaction; D011565:Psoriasis / Q000235:genetics / Q000473:pathology; D011944:Receptors, Androgen / Q000032:analysis / Q000235:genetics; D013234:Stem Cells / Q000166:cytology* / Q000473:pathology; D014960:X Chromosome
chemical_list: C410798:AR protein, human; D011944:Receptors, Androgen; D004247:DNA