Mapping of human thyroglobulin gene on the long arm of chromosome 8 by in situ hybridization

Summary We report the structural organization of a segment of the human thyroglobulin gene, located 70kb from the 3 end of the gene, containing the exons 8 and 9 starting from the 3 end. Selected probes from this region have been used for the chromosomal mapping of the thyroglobulin gene by in situ hybridization techniques. Only one site in the human haploid karyotype is labeled with the genomic DNA probes. Twenty percent of the grains are localized on the long arm of chromosome 8, mostly in the subregion q-2-23 q-2-24 of the long arm of chromosome 8. The localization of the autoradiographic grains suggests a subregional assignment of the human thyroglobulin gene locus to 8q 2–23 or 8q 2–24.     

Partial trisomy of the long arm of human chromosome 1 as demonstrated by in situ hybridization with 5S ribosomal RNA

Summary In a newborn boy with multiple malformations, a tandem duplication was detected at the distal end of the long arm of one human chromosome 1. The Giemsa bands, 1q31 to 1q43–44, were repeated serially. Since 5S rRNA genes are located at 1q42–43, in situ hybridization of ¹²⁵I 5S rRNA with fixed chromosome preparations was used to confirm the chromosomal duplication. The infant exhibited numerous developmental and clinical abnormalities as might be expected with an abnormality of chromosome structure relating to a ribosome component.     

Assignment of the human TYRP (brown) locus to chromosome region 9p23 by nonradioactive in situ hybridization.

The TYRP (brown) locus determines pigmentation and coat color in the mouse. The human homolog of the TYRP locus has been recently identified and shown to encode a 75-kDa transmembrane melanosomal glycoprotein called gp75. The gp75 glycoprotein is homologous to tyrosinase, an enzyme involved in the synthesis of melanin, forming a family of tyrosinase-related proteins. A genomic clone of human gp75 was used to map the human TYRP locus to chromosome 9, region 9p23, by nonradioactive fluorescent in situ hybridization. Specificity of hybridization was tested with a genomic fragment of human tyrosinase that mapped to a distinct site on 11q21. The 9p region has been reported to be nonrandomly altered in human melanoma, suggesting a role for the region near the TYRP locus in melanocyte transformation.     

Assignment of the human gamma-glutamyl transferase gene to the long arm of chromosome 22

Summary We have determined the chromosomal location of the human gene for gamma-glutamyltransferase (GGT). This study was done by in situ hybridization of human metaphase spreads with a rat cDNA probe specific for this enzyme and constructed from two clones previously characterized in our laboratory. The final construct had a 1.6-kb-long insert covering 92% of the coding sequence for GGT. The new insert was also freed of any GC tails introduced for the cDNA cloning, because we observed that these sequences were responsible for a high background. Using this probe for the analysis of 136 human metaphase spreads, we observed a strong specific signal on chromosome 22 at the interface of q111-112 and a minor peak in q131. Thus GGT might represent a new marker for the study of certain diseases which have chromosomal abnormalities at these loci.     

Assignment of the developmentally regulated gene NEDD1 to human chromosome 12q22 by fluorescence in situ hybridization

The developmentally regulated mouse gene Nedd 1 encodes a protein showing similarities with the -subunit of heterotrimeric GTP-binding proteins and has growth suppressing activity when overexpressed in various cultured cell types. We have mapped the human homolog (NEDD1) of the mouse gene to chromosome 12q22 by fluorescence in situ hybridization using R-banded human (pro)metaphase chromosomes.