SummaryWe have examined at the molecular level the CDR3 and adjacent regions in peripheral blood B lymphocytes of normal individuals. A total of 111 sequences (12-28 sequences from six individuals) were obtained after cloning of the polymerase chain reaction-amplified segments into plasmids or phage . The average length of the VDJ joining was 109 nucleotides, with a range from 79 to 151 . Approximately 75% of the sequences were in frame when translated into amino acids . Among the JH segments, J H4 was found most frequently (in 52 .5% of the sequences), and JH 1 and JH 2 segments the least frequently (-I% of the clones) . A polymorphic JH6 gene with a one-codnn deletion accompanied by a base change was present in two of six patients. Preferential breakpoints were found for JH 2, J.3, J 4, and Jx5, although the breakpoints of JH6 were distributed more heterogenously.In -90% of the cases, significant homology of the D regions with published D sequences was found . Preferential usage of a particular coding frame was observed in in-frame sequences utilizing DA, D21/9, and DMl segments. However, in general, all coding frames of germline D genes were used to generate CDR3s . Eight sequences that have a DN1-like D sequence with two base changes at the same positions were identified, suggesting the likely existence of a new germ line D gene belonging to the DN families. Using probes specific for a particular CDR3, the frequency of a specific B cell clone in the peripheral blood of normal individuals was estimated to be at most as high as 1/20,000 .T he most variable region of the immunoglobulin heavy chain is the third complementarity determining region (CDR3) (1, 2) . This region spans the junction between the variable (V ) diversity (D), and junctional 0,,) segments in the rearranged IgH genes (1, 2) . The hypervariability of this region is due to the combinatorial assortment of the many V , D, and JH segments that are utilized to generate a particular CDR3, to the imprecise joining mechanisms that include deletion of bases from the potential coding regions of each segment to be joined (3), and the addition of new bases that can be enzymatically added at the point of joining (N regions) (4) . Finally, somatic mutations of the rearranged region can contribute to the production of higher affinity antibodies (5) .The nucleotide sequences of all the human D genes, estimated to be -30 in number (6), have not been fully defined, and questions remain about the relative usage of different D genes used in VDJjoinings during development and in adult individuals . Furthermore, the characteristics of the extent of base excision and addition, including the identification of preferred sequence boundaries for the V., D, and J regions, have not been well delineated. The relative frequency of inframe translation products reflecting productive rearrangements, and the possibility of specific translation frames being preferred for particular D gene families have not been determined on a large sample size.To address these questions, we ha...

Beckwith-Wiedemann syndrome (BWS) is an autosomal dominant disorder of increased prenatal growth and predisposition to embryonal cancers such as Wilms tumor. BWS is thought to involve one or more imprinted genes, since some patients show paternal uniparental disomy, and others show balanced germ-line chromosomal rearrangements involving the maternal chromosome. We previously mapped BWS, by genetic linkage analysis, to 11p15.5, which we and others also found to contain several imprinted genes; these include the gene for insulin-like growth factor II (IGF2) and H19, which show abnormal imprint-specific expression and/or methylation in 20% of BWS patients, and p57KIP2, a cyclin-dependent kinase inhibitor, which we found showed biallelic expression in one of nine BWS patients studied. In addition, p57KIP2 was recently reported to show mutations in two of nine BWS patients. We have now analyzed the entire coding sequence and intron-exon boundaries of p57KIP2 in 40 unrelated BWS patients. Of these patients, only two (5%) showed mutations, both involving frameshifts in the second exon. In one case, the mutation was transmitted to the proband's mother, who was also affected, from the maternal grandfather, suggesting that p57KIP2 is not imprinted in at least some affected tissues at a critical stage of development and that haploinsufficiency due to mutation of either parental allele may cause at least some features of BWS. The low frequency of p57KIP2 mutations, as well as our recent discovery of disruption of the K(v)LQT1 gene in patients with chromosomal rearrangements, suggest that BWS can involve disruption of multiple independent 11p15.5 genes.

The complete disappearance of leukemic cells (or their reduction below our method's threshold of detection, 1 in 100,000 cells) may be necessary to achieve a cure of ALL. The quantification of residual leukemic cells in serial marrow aspirates during therapy may allow the early detection of relapse.