A recombinant plasmid containing sequences complementary to human pro-al(I) collagen mRNA was used for the chromosomal assignment of the pro-al(I) collagen gene. Restriction endonuclease analysis of DNA from mouse-human and Chinese hamster-human somatic cell hybrids revealed cosegregation with human chromosome 17. Hybrids containing derivative chromosomes with a t(2;17Xql4;q2l) translocation showed cosegregation ofthe pro-al(I) gene with the segment 17q21+qter. In situ hybridization on human metaphasic chromosomes confirmed this conclusion.At least five genetically distinct collagen types have been identified in mammals. Of these, type I collagen is the most abundant; it is the major constituent of bone, tendon, skin, and fibroblasts. It consists of two al(I) chains and one a2(I) chain, which are synthesized as precursor polypeptides containing NH2-and COOH-terminal propeptides and called pro-al(I) and pro-a2(I) chains (1,2).The availability of genomic libraries has permitted the isolation of the entire chicken pro-a2(I) gene (3-7) and part of the sheep pro-a2(I) (8) and of the mouse pro-al(I) genes (9). More recently, we have reported the isolation of specific cDNAs and genomic fragments for the human pro-a2(I) and pro-al(I) chains (10-13). However, one major question remains: Are the genes coding for the nine (or more) different polypeptide collagen chains dispersed in the genome or clustered as one or several gene family(ies)? Conflicting results have been obtained when immunological techniques were used to determine the chromosomal location ofthe pro-al(I) and pro-a2(I) genes (4, 5). We have used the more direct approach ofrestriction endonuclease analysis of DNA from human-rodent somatic cell hybrids hybridized to labeled cloned cDNAs. Using this method, we have unequivocally assigned the gene coding for pro-a2(I) collagen chain (COLIA2) to human chromosome 7 (14). In the present paper we report the assignment of the gene coding for the proal(I) chain (COLIAl) hybrids, or the parental cells were fused with polyethylene glycol (16) and hybrid cells were selected in ouabain/hypoxanthine/aminopterin/thymidine medium (17) for the other hybrids. For counter-selection, hybrid cells L-53 were grown in standard medium supplemented with 5-bromodeoxyuridine (18). Cell lines were established and maintained as described (18)(19)(20). Cell hybrids were characterized by isozyme and karyotype analysis. Chromosomes were identified by R-banding (21).Recombinant Clones and DNA Analysis. From a human fibroblast cDNA library five overlapping clones specific for the pro-al(I) chain were isolated (12). The clones were characterized by restriction endonuclease mapping and direct DNA sequence analysis was performed according to Maxam and Gilbert (22). Here we have used one of these clones (Hf-677). Nuclear DNA purification and restriction endonuclease analysis were performed as described (14).In Situ Hybridization on Metaphase Chromosomes. A phytohemagglutinin-stimulated culture ofwhole blood from a normal woman was ...

A specific enzyme immunoassay of uroporphyrinogen decarboxylase was developed and applied to the detection of the human enzyme in man-rodent somatic cell hybrids. This method allowed to assign the gene for uroporphyrinogen decarboxylase to human chromosome 1.

We used a cloned human cDNA probe homologous to the placenta chorionic gonadotropin beta subunit (CGB) and to the pituitary luteinizing hormone beta subunit (LHB) and Southern blotting techniques to analyse DNA from a series of rodent X human somatic cell hybrids for the presence of specific gonadotropin beta subunit related sequences. Our results provide evidence for the assignment and linkage of the eight genes (or pseudogenes) coding for the beta subunit of these glycoprotein hormones to chromosome 19. Moreover, we observed a strict concordance between the permissivity of mouse X man hybrid cells to enteroviruses (which is linked to the presence of specific cell receptors encoded by human chromosome 19) and the presence of CGB and LHB related sequences, thus confirming the localization of the structural genes for the beta subunits on chromosome 19.

Summary A method of specific immunoprecipitation of minor isozymes was developed and applied to the detection of human F‐type phosphofructokinase in man‐rodent somatic cell hybrids. This method allowed us to assign the gene for this newly discovered isozyme of phosphofructokinase to chromosome 10.