title: Relationship between monoamine oxidase (MAO) A specific activity and proportion of human skin fibroblasts which express the enzyme in culture.
abstract: Total deficiency of monoamine oxidase A (MAO-A) in affected males of a single, human kindred appears to be associated with mild mental retardation and significant behavioral anomalies. Though total MAO-A deficiency appears to be rare, the extent and significance of individual variation in monoamine oxidase A activity in human populations is unclear. Since MAO-A activity is undetectable in blood cells, most systematic surveys of individual variation MAO-A activity have compared enzyme activity in human fibroblasts cultured from skin biopsies. Surprisingly, MAO-A activity in skin fibroblast cultures from unrelated donors ranges over 100-fold. It has been suggested that this extreme variation in fibroblast MAO-A activity between donors reflects individual, genetic variation in the regulation of MAO-A in fibroblasts. I have found from studies with immunofluorescence microscopy and flow cytometry that the proportion of MAO-A+ cells in fibroblast cultures is (a) highly variable between cultures, (b) a reproducible characteristic of each culture and (c) the primary factor responsible for variation in MAO-A specific activity in whole cell, skin fibroblast homogenates. It has been shown previously that MAO-A activity of a skin fibroblast culture is relatively constant with continued passage prior to cellular senescence. Therefore, these new data raise the possibility that MAO-A expression is confined to a functionally distinct subset of human skin fibroblasts.
authors.affiliation: Graduate School of Biomedical Sciences, Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Denney
mesh_terms: D002478:Cells, Cultured; D002648:Child; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007223:Infant; D007527:Isoenzymes / Q000096:biosynthesis / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D008995:Monoamine Oxidase / Q000096:biosynthesis / Q000378:metabolism*; D012016:Reference Values; D012867:Skin / Q000166:cytology / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D008995:Monoamine Oxidase