Manipulation of Human Chromosomes by Dyes and Cell Sorting

The study of human chromosomes was pursued actively by Dr. Samuel Latt over the many years of his tenure in the Children's Hospital IDDRC (Ann. Rev. Biophys. Bioengr., 1976; Ann. Rev. Gen., 1981; Banbury Report, Cold Spring Laboratory, 1983). Latt was initially recruited as a "new investigator" in the Center and before his untimely death had risen to become the Director of the IDDRC Genetics Program. From early work with DNA binding dyes, which stained different regions of human chromosomes, Latt developed methods that enabled him to follow the replication pattern of DNA within the chromosome. This interest in DNA binding dyes and newly developed means to detect these dyes within cells led to the application of these procedures to fluorescence-activated cell sorting to track the cell cycle more accurately by following the fluorescence intensity of newly-synthesized DNA. A natural extension of this work was the use of DNA binding dyes to separate each of the human chromosomes by DNA content and to prepare these chromosomes in sufficient quantities to make them available for manipulation of their contained DNA. This accomplishment enabled sufficient DNA to be obtained for the establishment of libraries of cloned DNA from each human chromosome. The research of the Genetics Program of this IDDRC then focused on a few specific chromosomes where important human disease genes were known to be located. This work was the model for the development of the governmental resource of libraries for all of the human chromosomes. Indeed, Latt served as an advisor to this project and was instrumental in its implementation. From the libraries, cloned segments could be obtained from specific chromosomes. These cloned segments were then used as a genetic marker for the region from which the segment was derived. These markers became instrumental in the identification of the gene for Duchenne dystrophy by Dr. Kunkel, and ultimately the identification of a large number of different disease genes. This work is being extended in many different ways in the current IDDRC.