A genetic study of the RA cell, a new line of human amnion, with special reference to cytogenetics, radiation effects and enzyme systems

Abstract

When working with a continuous line of human cells, it is particularly useful to be able to secure an adequate supply of normal primary tissue of the same kind. Thus genetic characteristics such as chromosome constitution and the presence or absence of certain enzymes can be compared in the primary and continuous cells. With such epithelioid lines as Chang liver (Chang, 1954) or the several lines derived from human marrow by sternal puncture (Szybalski, 1963), the securing of comparative primary tissue is troublesome. By contrast human amnion cells are easy to obtain in large quantities from normal placentae. The number of continuous lines of spontaneously altered human amnion cells that have been reported in the literature is surprisingly small. Only five are listed by Hayflick and Moorhead (1962) and only three have appeared with any frequency; the FL line (Fogh and Lund, 1957) the WISH amnion (Hayflick, 1961) and the Fernandez line (Fernandez, 1958). Not all of these are equally useful, e.g., one investigator (Loh, personal communication) has found the FL cell to be somewhat poor in cultural properties for virological studies. It is therefore believed that continuous lines of spontaneously altered human amnion cells with favorable growth characteristics and relatively minimal fastidious care can be extremely useful in studies of human genetics in vitro, and in other areas of inquiry. The purpose of this report is to describe in detail such a line of cells, the RA cell. A brief description could be given in a paragraph, relating the origin of the cells and stating the medium required for their cultivation. In fact, a considerable number of cell lines have appeared in the literature with little or no description. This occurrence seriously limits their usefulness, however. In this regard it is of interest that some recent studies of some well-known cell lines, using immunological and cytogenetic methods have yielded rather surprising results. Brand and Syverton (1962) found that 17 lines of cells supposedly derived from human, monkey, rabbit, swine, calf, hamster and duck tissues did in no case belong to the supposed species of origin but were either mouse or human cells. Several otherwise excellent genetic studies have appeared where the cell being used could simply no longer be identified (Lieberman and Ove, 1959, 1959a). It is believed, therefore, that a more extensive description of the RA cell is justified. In addition to the merely descriptive material, experimental studies with the RA cell reported here indicate the cell can be very useful for several aspects of cell culture genetics, including cytogenetic, x-ray resistance and enzyme studies.