The human lambda L chain Ig locus. Recharacterization of JC lambda 6 and identification of a functional JC lambda 7

Area of Science:

• Immunogenetics
• Molecular Biology
• Human Genetics

Background:

• The human immunoglobulin lambda L chain gene complex comprises multiple JC gene segments.
• Previous research identified C lambda 6, associated with Kern+Oz- proteins.

Purpose of the Study:

• To identify and characterize novel human lambda C region gene segments.
• To investigate the functionality of C lambda 7 and C lambda 6 gene segments.
• To clarify the genetic basis of Kern+Oz- myeloma proteins.

Main Methods:

• Gene mapping and sequencing of lambda C region gene segments.
• Analysis of recombination sites and RNA splice sites.
• Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis.
• Genomic DNA analysis from multiple cell lines and patient samples.

Main Results:

• A novel gene segment, C lambda 7, was identified 2.7 kb downstream of C lambda 6, with an upstream J lambda 7 segment.
• C lambda 7 maintains an open reading frame, encodes Kern+ and Oz- determinants, and is transcribed in normal lymphocytes.
• A 4-bp insertion was found in C lambda 6, rendering it non-functional in the cosmid clone and verified in genomic DNA samples.
• Kern+Oz- myeloma proteins may not define a distinct isotype or be encoded by C lambda 7.

Conclusions:

• JC lambda 7 represents a functional gene segment encoding a new lambda isotype.
• C lambda 6 is likely non-functional due to a specific DNA insertion.
• The genetic basis and isotype classification of Kern+Oz- myeloma proteins require further investigation.