Heterozygous mutations in the DNA binding domain of STAT6 in PMBL. (A) Electropherograms showing partial STAT6 cDNA sequences for the 4 most frequently mutated codons (underlined). Mixed nucleotides are lettered according to International Union of Pure and Applied Chemistry (IUPAC) international code. *This sequence was performed by PCR amplification of genomic DNA (no RNA available). (B) Schematic localization of mutations in the region spanning nucleotides 1216 to 1581, corresponding to exon 12 (minus 4 bases in the 5′ dark gray part), exon 13, and exon 14 (minus 26 bases in the 3′ dark gray part) of STAT6 in the 20 mutated PMBL cases. *This case presents both a missense mutation of codon 419 and a silent mutation of codon 423 (c.A1269G, according to NM_003153.3).