Springer Online Journal Archives 1860-2000
Abstract The Igk-J locus of the mouse encodes the immunoglobulin κ light chain joining (J) segments. Four Igk-J alleles have been described on the basis of restriction enzyme length polymorphisms. The nucleotide sequences of the Igk-J a allele (type strain, C.C58), Igk-J c allele (type strain, SJL/J), and Igk-J d allele (type strain, SK/CamRk) have been determined and are compared with the previously reported Igk-J b allele sequence (type strain, BALB/c). The mouse sequences are also compared with published sequences for rat and human J k sequences. Far more differences were found between the Igk-J a allele and the other mouse alleles than between any two of the latter. These result in two amino acid substitutions which distinguish the J2 and J3 1 segments of the Igk-J a allele from the other three alleles. Use of the Phylogenetic Analysis Using Parsimony program to generate a phylogenetic tree strongly indicates that after divergence from the rat ancestor, there appears to have been an early split between the Igk-J a allele and the evolutionary precursor of the other mouse alleles. There also appears to have been far less divergence from the ancestral condition in the Igk-J a allele than in the other alleles. Also, the presence of only one convergent mutation among the four mouse alleles provides strong evidence against any crossing over within the Igk-J locus during the history of these alleles. Finally, the differences in rates of evolution of the Igk-J alleles are in marked contrast to the relatively uniform rates of divergence of four alleles of a mouse V k gene, Igk-VSer.
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