ABSTRACT
To examine the X-inactivation patterns of normal human nails, we performed the human androgen receptor gene assay of DNA samples extracted separately from each finger and toe nail plates of nine female volunteers. The X-inactivation pattern of each nail was unique and constant for at least 2 years. The frequency of nails with one of the two X-chromosomes exclusively inactivated was 25.9%. In the nails composed of two types of cells with either one X-chromosome inactivated, the two cell types were distributed in patchy mosaics. These findings suggest that the composition of precursor cells of each nail is maintained at each site at least through several cycles of regeneration time, and that the nail plate has a longitudinal band pattern, each band consisting of cells with only one of the two X-chromosomes inactivated. Using the frequency of nails with one of two X-chromosomes exclusively inactivated, we estimated the number of progenitor cells that gave rise to the nail plate during development to be about 3, under the assumption that the process follows the binominal distribution model. A strong correlation observed among the big, index and little fingers, and among the corresponding toes suggests an interesting interpretation concerning their morphogenetic process.
Subject(s)
Nails/metabolism , X Chromosome Inactivation , Female , Humans , Male , Nails/cytology , Nails/embryology , Receptors, Androgen/genetics , Stem CellsABSTRACT
Sensitivity to the bitter taste of chloramphenicol was studied in 860 students, 620 males and 240 females. About 8.6% of them were insensitive to this bitter taste. Familial lineage studies were carried out on a subset of these students, and the results suggested that the sensitivity or insensitivity was controlled by a pair of autosomal Mendelian genes, with the sensitive gene being dominant over the insensitive.
