Schematic presentation of SOCS1 mutations in L&H cells. The complete coding region of SOCS1 was amplified and sequenced from genomic DNA of single micromanipulated L&H cells of 12 cases and the lpHL-derived cell line DEV. (A) A scheme of the SOCS1 protein with functionally important regions and the 3 PCR fragments amplified are shown at top (P rich indicates proline rich; KIR, kinase inhibitory region; and ESS, extended SH2 domain). For each case with mutations in SOCS1, only regions and alleles that carried mutations are presented. Mutations are indicated by ▴. The deletion in case 3 is of germ-line origin. Protein sequences translated out of frame due to deletions or duplications are shown in − − − and stop codons, by †. In addition to the mutated alleles, unmutated alleles were amplified for the central region (CR) of case 1 (7×), the N-terminal region (NTR) of case 2 (3×), the NTR of case 3 (1×), the CR of case 4 (1×), the NTR and CR of case 5 (1× and 2×), and the NTR and C-terminal region (CTR) of case 6 (2× and 3×). Amplification of only 1 unmutated allele for a fragment of a case (NTR of case 3, CR of case 4, and NTR of case 5) is most likely due to cellular contamination during micromanipulation. Apart from the replacement mutations shown, altogether 7 silent mutations were observed (not shown; see Table S2 for details). For alleles with ongoing somatic mutation, the variant carrying the most mutations is always presented. (B) Stepwise accumulation of mutations for alleles with intraclonal diversity is shown. Presence of truncating and replacement mutations in functional important regions of SOCS1 suggest that SOCS1 function is impaired in L&H cells.