Abstract
The characterization and expression of human immunoglobulin lambda ($\lambda$) and lambda-like genes are presented. The human immunoglobulin lambda gene locus had been previously described as containing six JC genes, with genes JC$\lambda$1, 2, 3, and 6 encoding the Mcg, Kern$\sp-$Oz$\sp-$, Kern$\sp-$Oz$\sp+$, and Kern$\sp+$Oz$\sp-$ myeloma proteins.In contrast, we determined JC$\lambda$6 was a pseudogene by DNA subcloning of the gene and Southern blots of 32 different genomic DNA samples. JC$\lambda$6 was found to contain a four base-pair insertion creating an inframe TAG termination codon in the C region.We further identified a new $\lambda$ gene, JC$\lambda$7, found downstream of C$\lambda$6. DNA sequencing of the JC$\lambda$ regions of $\lambda$7 revealed it was a potential functional gene since it contained consensus recombination signals, RNA splice sites and maintained open reading frames throughout its coding regions. We showed that JC$\lambda$7 was transcriptionally expressed by four independent analyses.In a separate set of studies, other genes, called $\lambda$-like genes, were characterized and analyzed for expression in pre-B and B cell tissues. These gene products may be involved in pre-B cell development. We found a new $\lambda$-like gene, 16.2, in addition to the $\lambda$-like genes 14.1 and 16.1 previously described. To determine the transcription of all three $\lambda$-like genes in various pre-B cell sources, we used specific restriction enzyme digests of cDNA PCR products to distinguish these genes. Pre-B cell lines (ALLs, acute lymphocytic leukemias) were found to transcribe only gene 14.1. In contrast, fetal liver hybridomas were found to transcribe only gene 16.2. Examination of fetal liver tissue revealed the presence of both gene 14.1 and 16.2 transcripts, but a total lack of gene 16.1 transcripts.The use of somatic cell hybrid panels and pulse-field gel electrophoresis revealed the $\lambda$-like genes are grater than 700 kb distal to the JC$\lambda$ locus on chromosome 22q11.2, and 14.1 and 16.2 genes reside within a 210 kb restriction fragment, and gene 16.1 is at least 200 kb distal to genes 14.1 and 16.2.In conclusion, we found the human immunoglobulin lambda gene locus contains a fourth functional gene, JC$\lambda$7, in addition to JC$\lambda$1, 2, 3 and that two lambda related genes, 14.1 and 16.2, are transcribed in pre-B cells.