Localization ofhumanimmunoglobulin Klight chainvariable region genes totheshort armofchromosome 2by insitu hybridization

Thegenes forhumanimmunoglobulin Klight chains have been localized innormal lymphocyte andfibroblast chromosomes byinsitu hybridization ofprobes from cloned DNA fragments oftheKvariable region locus. Thelocalization was achieved bycounting grains (after autoradiography) overchro- mosomes inanumber ofkaryotypes.. Thevariable region gene probes hybridized inacluster onaregion ofthechromosome 2 short armclose tothecentromere (2cenvp12). This location was confirmed inlymphocytes fromabalanced translocation carrier 46XXt (2; 16) (q13; q22). Ourresults show that human Klight chain genes arelocated intheregion ofthebreak point observed inspe- cific chromosomal translocations associated with Burkitt lymphoma. Thethree sets ofunlinked genes code for antibody proteins: the heavy chain, theKlight chain, andtheAlight chain genes. Attempts tomapthese genes inmanhave been hindered bythe lack ofvariants suitable for family studies andtheloss ofim- munoglobulin expression insomatic cell hybrids. Despite these problems, chromosome assignments forsomehumanimmu- noglobulin genes have beenmadebyusing panels ofmouse- humanhybrid cell lines with different humanchromosome complements. Correlation between immunoglobulin expres- sion andthepresence ofspecific humanchromosomes inhy- brids ofmouse myeloma cells andhuman Bcells hasledtoas- signment ofAlight chains tochromosome 22(1) andofheavy chains tochromosome 14(2). Humanheavy chain genes have also been assigned tochromosome 14onthebasis offilter hy- bridizations between cloned heavy chain genes andDNAfrom apanel ofmouse-human hybrid cell lines with different human chromosome complements (3). Acompletely different technique-with theadvantage of using normal cells rather than apanel ofhybrid cell lines-is that ofinsitu hybridization tofixed metaphase chromosomes. This technique previously hasbeen used toconfirm thelocation ofhuman a-and/3-globin genes totheir respective chromo- somes (4, 5). Inthis paper wedescribe thelocalization ofhuman Klight chain genes byinsitu hybridization. Twocloned genomic DNAfragments, each containing asingle Kvariable region (VK) gene, wereused ashybridization probes. Theresults ofthein situ hybridization withthese VKprobes localize theKchain genes tochromosome 2inman.