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Twenty independent man-mouse (Cl1D,LA/TK-, HPRT-) and man-hamster (CH,HPRT-) hybrids using female human cells with balanced reciprocal translocation XX,t(X;5)(q21;q11) were analyzed for human genes localized on chromosome 5 (HEXB), on chromosome X (PGK, GALA, HPRT, G6PD) and for the different chromosomes in relation with the balanced reciprocal translocation (chr.5, chr.5q-, chr.Xq+, chr.X). The different results obtained indicate that the genes for human markers HEXB, PGK are on Xq+, and that the genes for human markers GALA, G6PD are on 5q-. These data implicate finally the following localizations: HEXB on 5q11 leads to 5qter; PGK on Xq21 leads to Xpter; GALA, HPRT, G6PD on Xq21 leads to Xqter.

An analysis of 20 independent man-mouse and man-hamster hybrids has shown that the gene coding for the cell-surface protein CD9(p24), a differentiation antigen recognized by the monoclonal antibody ALB6, is located on chromosome 12. A positive correlation was shown between CD9(p24) and chromosome 12 and all other chromosomes were excluded. In addition a synteny was observed between CD9(p24) and LDH-B, a well known marker of chromosome 12 (out of 27 hybrids, 15 were LDH-B+ ALB6+ and 12 were LDH-B-ALB6-). Expression of the antigen in hybrid CH-35K issued from parental fibroblasts possessing a balanced reciprocal translocation 46,X,Y,t(X,12)(q23,q12) indicated that the gene for CD9(p24) is probably localized on 12q12----pter. Monoclonal antibodies ALB6, Ba2 and 602/29 recognize the same protein of molecular weight 21 to 24 KD controlled by a gene located on chromosome 12. It is known that Ba2 and 602/29 recognize two different epitopes but the existence of a third epitope recognized by ALB6 remains to be shown.

Analysis of human-rodent hybrids showed the following: the assignment of the ADA1 structural gene to chromosome 20; the identification in hybrids of a new ADA, referred to as ADAx, with a migration more rapidly anodal than ADAd and less rapidly anodal than ADA1 (product of allele 1 or 2); ADAx and d are formed by ADA1 and ADCP (an adenosine deaminase complexing protein). ADCP synthesis is controlled, at least, by a gene (ADCP2) localized on chromosome 2, probably in the IDH1 region; the combined action of another gene (ADCP1), assigned by other authors to chromosome 6, could be neither proved nor disproved, if this gene exists, it must be on 6p or in the 6qter region; the presence of chromosomes 20, 2, and 6 does not constitute a sufficient condition for the formation of ADAx and d, in either the hybrids or the human strains or lines: other factors intervene in its formation, i.e., an interaction between the culture medium, the human parental strain or line, and the rodent parental line.

The value of man-rodent hybrids for detecting creatine kinase BB (CKBB) was greatly increased by the use of an agar technique, in extended incubation (20 hours) with a concentrated solution of creatine as substrate (8 mg/ml instead of 1 mg/ml as usual). The selection of a man-rodent hybrid without discordant between chr. 14 and nucleoside phosphorylase (NP) (a marker of this chromosome) contributed efficiently to the detection of the positive correlation between CKBB and chr. 14/NP. Among 22 independent hybrids, the following were observed : 8 NP + CKBB+, 3 NP + CKBB(+), 11 NP-CKBB- and 6 chr. 14 + CKBB+, 2 chr. 14 + CKBB(+), 11 chr. 14 CKBB-, 2 chr. 14/CKBB+ and 1 chr. 14/CKBB(+). The presence of the chromosome was noted + or - according to its presence in more or less than 30% of the cells. These results show that the gene for CKBB is located on chr. 14 and that the presence of this single chr. 14 is sufficient for the expression of human CKBB in man-rodent hybrids. Discordant results reported by others (Povey et al., 1979) may be due to the weakness of the human CKBB detection in man-rodent hybrids or to the bad conservation of this enzyme.

To increase the efficiency of the human gene mapping, a panel of 25 man-rodent hybrids was selected out of 200 independent man-rodent hybrids produced in our laboratory since 1969. The hybrid panel was selected in such a fashion as to allow the asignment of a human marker M by respecting the two following complementary criteria: correlation between M and a chromosome and exclusion of the other chromosomes. The panel characteristics allowing the use of these two criteria were presented and discussed. A first series of enzyme markers were analysed to test the validity of the hybrid panel for the human gene mapping. The different possibilities and limits of the hybrid panel were also discussed, especially for the assignment of markers with DNA probes.

Analysis of different human tissues showed that glutathione S-transferase (GST) of fibroblasts and leucocytes is GST3, an enzyme found in liver extracts by Board (1981). Consequently, the GST localized on human chromosome 11 by Silberstein and Shows (1981, 1982) is GST3. Analysis of tissue extracts showed a new GST band, very intense in muscle extracts and very weak or absent in other tissues, and called GSTM. Analysis of man-rodent hydrids showed synteny between LDHA, GST3, ESA4 and localization of this synteny group on chromosome 11. Analysis of discordant percentages and discordant types between markers favored the following assignments: LDHA on 11p12, GST3 on 11q13 leads to 11qter, ESA on 11q13 leads to 11q22. The present study suggests assignment of GST3 to 11q13 leads to 11q22. Different types of man-rodent hybrids are useful for human gene mapping. A new type hybrid, as used here (nonadhering to glass or plastic surfaces), appears useful because of rapid proliferation and growth in suspension, the latter feature facilitating culture and harvesting.