Human MUC4 mucin cDNA and its variants in pancreatic carcinoma.
The human MUC4 gene is not expressed in normal pancreas; however, its dysregulation results in high levels of expression in pancreatic tumors. To investigate the tumor-associated expression, MUC4 cDNA was cloned from a human pancreatic tumor cell line cDNA expression library using a polyclonal antibody raised against human deglycosylated mucin and RT-PCR. Pancreatic MUC4 cDNA shows differences in 12 amino acid residues in the non-tandem repeat coding region with no structural rearrangement as compared with tracheal MUC4. The full-length MUC4 cDNA includes a leader sequence, a serine and threonine rich non-tandem repeat region, a central large tandem repeat domain containing 48 bp repetitive units, regions rich in potential N-glycosylation sites, two cysteine-rich domains, EGF-like domains, and a transmembrane domain. We also report the presence of a new EGF-like domain in MUC4 cDNA, located in the cysteine-rich region upstream from the first EGF-like domain. Four distinct splice events were identified in the region downstream of the central tandem repeat domain that generate three new MUC4 cDNA sequences (sv4, sv9, and sv10). The deduced amino acid sequences of two of these variants lack the transmembrane domain. Furthermore, two unique forms of MUC4 (MUC4/Y and MUC4/X) generated as a result of alternative splicing lack the salient feature of mucins, the tandem repeat domain. A high degree of polymorphism in the central tandem repeat region of MUC4 was observed in various pancreatic adenocarcinoma cell lines, with allele sizes ranging from 23.5 to 10.0 kb. MUC4 mRNA expression was higher in differentiated cell lines, with no detectable expression in poorly differentiated pancreatic tumor cell lines.
Choudhury
A
A
Department of Biochemistry and Molecular Biology, Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198-4525, USA.
Moniaux
N
N
Winpenny
J P
JP
Hollingsworth
M A
MA
Aubert
J P
JP
Batra
S K
SK
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D015152:Blotting, Northern; D018076:DNA, Complementary / Q000235:genetics*; D004815:Epidermal Growth Factor / Q000235:genetics; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D055264:Mucin-4; D009077:Mucins / Q000235:genetics*; D010190:Pancreatic Neoplasms / Q000235:genetics*; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D018076:DNA, Complementary; C524658:MUC4 protein, human; D055264:Mucin-4; D009077:Mucins; D004815:Epidermal Growth Factor