Report of the committee on the genetic constitution of chromosomes 7, 8 and 9

Abstract

The principal assignment to human chromosome 7 since the last workshop has been the locus for cystic fibrosis (CF). The linkage of PON and CF was established at HGM8 (Eiberg et al. 1985) but the linkage group could not be assigned to a chromosome. The localization of CF and PON on chromosome 7 was demonstrated through linkage to a randomly isolated DNA segment, DOCRI-917 (now D7S15; Tsui et al. 1985), which was assigned to chromosome 7 (Knowlton et al. 1985). There are two new confirmed locus assignments on chromosome 8. Wilson et al. (1986) used human-Syrian hamster and human-Chinese hamster somatic cell hybrids to map the gene for beta-glycerol phosphatase (GPB). The enzyme catalyses the hydrolysis of beta-glycerol phosphate and their studies indicated that it may be a dimer. Wijnen et al. (HGM9) screened a panel of Chinese hamster - human hybrids and observed a discordance in segregation for GPB with every human chromosome except chromosome 8. Two other assigned loci GSR and PLAT co-segregated with GPB without exception. The results from one subclone suggests that GPB may be on the long arm of the chromosome (Wilson et al. 1986). The location of the glutamic-pyruvate transaminase locus (GPT) has finally been confirmed on chromosome 8 by linkage studies with TG and D8S19, with a lod for GPT-D8S19 greater than 3 at 22% recombination (O'Connell et al. HGM9; O'Connell, personal communication). Three new loci have been mapped to chromosome 9. Galactosyltransferase (GGTB2) was mapped by in situ hybridization studies (Duncan et al. 1986) using a cDNA probe and confirmed by Shaper et al. (1986) using a bovine probe. The gene maps to 9p21-p13. Two abstracts presented at this meeting map the fifth component of complement to the long arm of 9. Linkage between the ABO blood group and dopamine-beta-hydroxylase (DBH) has been suggested (Elston et al. 1979) and confirmed (Asamoah et al. 1987; Goldin et al. 1982). Data presented at the meeting assign DBH to 9q34 by in situ hybridization with a cDNA clone (Craig et al., personal communication) indicating that it is the structural DBH locus on 9. The regional assignment of delta-aminolevulinate dehydratase (ALAD, Wang et al. 1985) is confirmed by in situ hybridization of 9q34 (Potluri et al. 1987).