SALL4 has 2 isoforms. Alternative splicing generates 2 variant forms of SALL4 mRNA. (A) SALL4A and SALL4B vary in protein length and in the presence of different numbers of characteristic sal-like zinc finger domains. SALL4A (encoding 1067 amino acids) contains 8 zinc finger domains, while SALL4B (encoding 623 amino acids) has 3 zinc finger domains. Both variants have exons 1, 3, and 4, and SALL4A contains all exons from 1 to 4. However, SALL4B uses an alternative splice donor that results in deletion of the large 3′ portion of exon 2. (B) RT-PCR analysis of SALL4 variants in different human tissues. Four exons of SALL4 and their potential coding structures are illustrated, with arrows indicating the primers used for PCR amplification of the SALL4 transcripts (i). Tissue-dependent expression of SALL4 transcripts by RT-PCR (ii). A 315-bp expected product that was specific for SALL4A with primers A1 (exon 2) and B1 (exon 4) was amplified with cDNAs of various tissues. Primers D1 (exon 4) and C1 (exon 1) were used to amplify the 1851-bp expected product of SALL4B. Comparable amounts of cDNA were determined by GAPDH. (C) SALL4 protein products, SALL4A, and SALL4B identified by a SALL4 peptide antibody. Lysates from Cos-7 cells transiently expressing His-SALL4B (lane 1), His-SALL4A (lane 2), or control vector (lane 8), or lysates from different human tissues were resolved by 10% SDS-PAGE gel, transferred onto a nitrocellulose membrane, and probed with the N-terminal SALL4 peptide antibody.