In this report 118 mouse V O genes are described which, together with the 22 V O genes reported previously (T. Kirschbaum et al., Eur. J. Immunol. 1998. 28: 1458-1466 amount to 140 genes that had been cloned and sequenced in our laboratory. For 73 of them cDNAs are known, i. e. they have to be considered functional genes, although 10 genes of this group have 1-bp deviations from the canonical promoter, splice site or heptanucleotide recombination signal sequences. Twenty V O genes have been defined as only potentially functional since they do not contain any defect, but no cDNAs have been found (yet) for them. Of the 140 V O genes 47 are pseudogenes. There are indications that two to five V O genes or pseudogenes exist in the O locus which we have not yet been able to clone. The 140 V O genes and pseudogenes were assigned to 18 gene families, 4 of them being one-member families. This differs from previous enumerations of the families only by the combination of the V O 9 and V O 10 families and by the addition of the V O dv gene as a new separate family. Sequence identity usually was 80 % or above within the gene families and 55-80 % between genes of different families. Many of the mouse V O gene families show significant homologies to the human ones, indicating that in evolution V O gene diversification predated the divergence of the primate and rodent clades.

At the present state of analysis the central part of the kappa locus comprises four contigs of together 1.2 Mb and contains 55 Vkappa genes. It is flanked by the 3' part of the locus with 22 Vkappa genes in 0.4 Mb (T. Kirschbaum et al., Eur. J. Immunol. 1998. 28: 1458-1466) and the 5' part with 63 Vkappa genes in six contigs of together 1.5 Mb (F. Röschenthaler et al., accompanying report). The 5' and the central regions have one large contig in common. A part of the central region is linked to the 3' region resulting in a 1.1-Mb contig. The structure of the contigs was established mainly by the analysis of overlapping cosmid clones derived from genomic DNA and yeast and bacterial artificial chromosomes (YACs and BACs) and by PCR techniques. Pulsed-field gel electrophoresis of YAC digests indicated that three gaps between the contigs of the central region are 10-40 kb in size, comprising together about 90 kb. Internal duplications in this part of the locus and rearranged YACs were the major problems of the structural work. Structural details are to be found on the Internet at http://www.med.uni-muenchen.de/biochemie/zach au/kappa.htm. In a concluding section of the report the mouse kappa locus is compared to the human one and some aspects of the evolution of the kappa locus are discussed.

V B genes and pseudogenesThe characteristics of the V O genes and pseudogenes of the mouse O locus are compiled in Table A1. Some V O 8 and V O 19/28 genes and all V O 21 genes have previously been reported [7]. The features of the gene families and some general properties of the V O genes are described in the main part of this report. Some quotations in the Appendix are to references in the main part of the report; most of them, however, are listed below as [A1] etc. Additional information on the V O genes and their locations within the locus is given in the Internet at

A detailed restriction map of a 430-kb contig comprising the single C O , the 5 J O and the adjoining 22 V O gene segments is presented. The first 12 V O genes following the J O C O region belong to the V O 21 family, the subsequent ones to the closely related families V O 8 and V O 19/ 28. Previous difficulties in cloning all V O 21 genes can now be explained by the presence of a duplicated region in this part of the locus. The structure was established by analysis of yeast artificial chromosome, bacterial artificial chromosome and cosmid clones and by the so-called long template PCR technique. The distance between C O and the proximal V O 21 gene is 22 kb and the average distances between the V O genes are about 20 kb. Of the 12 V O 21 genes 5 were sequenced for the first time and 8 of the 12 genes were found to be expressed. Of the 10 V O 8 and V O 19/28 germline genes 9 are new; expression products of 8 of the 10 genes were known. The known 5', 3' polarities allow to specify for the 22 V O genes whether they are rearranged to the J O C O element by a deletion or an inversion mechanism. Also the formation of interesting rearrangement products in classical cell lines as MPC11, MOPC41 and PC 7043 can be explained now. The non-V O sequence L10 whose rearrangement by inversion has been described earlier (Hoechtl and Zachau, Nature 1983. 302: 260-263) was now localized downstream of J O C O .