Rabbit Anti-Human CDX2 Monoclonal Antibody, clone CQ7134

Background The homeobox genesPdxandCdxare widespread across the animal kingdom and part of the small ParaHox gene cluster. Gene expression patterns suggest ancient roles forPdxandCdxin patterning the through-gut of bilaterian animals although functional data are available for few lineages. To examine evolutionary conservation ofPdxandCdxgene functions, we focus on amphioxus, small marine animals that occupy a pivotal position in chordate evolution and in which ParaHox gene clustering was first reported. Results Using transcription activator-like effector nucleases (TALENs), we engineer frameshift mutations in thePdxandCdxgenes of the amphioxusBranchiostoma floridaeand establish mutant lines. HomozygousPdxmutants have a defect in amphioxus endoderm, manifest as loss of a midgut region expressing endogenous GFP. The anus fails to open in homozygousCdxmutants, which also have defects in posterior body extension and epidermal tail fin development. Treatment with an inverse agonist of retinoic acid (RA) signalling partially rescues the axial and tail fin phenotypes indicating they are caused by increased RA signalling. Gene expression analyses and luciferase assays suggest that posterior RA levels are kept low in wild type animals by a likely direct transcriptional regulation of aCyp26gene by Cdx. Transcriptome analysis reveals extensive gene expression changes in mutants, with a disproportionate effect ofPdxandCdxon gut-enriched genes and a colinear-like effect ofCdxon Hox genes. Conclusions These data reveal that amphioxusPdxandCdxhave roles in specifying middle and posterior cell fates in the endoderm of the gut, roles that likely date to the origin of Bilateria. This conclusion is consistent with these two ParaHox genes playing a role in the origin of the bilaterian through-gut with a distinct anus, morphological innovations that contributed to ecological change in the Cambrian. In addition, we find that amphioxusCdxpromotes body axis extension through a molecular mechanism conserved with vertebrates. The axial extension role forCdxdates back at least to the origin of Chordata and may have facilitated the evolution of the post-anal tail and active locomotion in chordates.

The special AT-rich sequence binding protein (SATB2) has been reported to be a specific immunohistochemical marker for colorectal carcinoma; however, correlation of SATB2 expression with molecular alterations commonly assessed in colorectal carcinoma has not been performed. We examined the immunohistochemical expression of SATB2 in 586 adenocarcinomas of the gastrointestinal (GI) tract and pancreas to assess its utility in diagnosis and analyze the clinicopathologic and molecular characteristics of colorectal carcinoma stratified by SATB2 expression. SATB2 and CDX2 expression were evaluated in 266 adenocarcinomas of lower GI tract origin (246 colorectal and 20 appendiceal mucinous), 208 adenocarcinomas of upper GI tract and small intestinal origin (74 esophagus/esophagogastric junction, 103 stomach, 20 duodenal, and 11 jejunoileal), and 112 pancreatic ductal adenocarcinomas. SATB2 expression was more frequently identified in adenocarcinomas of lower GI tract origin (222/266, 83%) compared with upper GI tract, small intestinal, or pancreatic origin (26/320, 8%) (P < 0.001). Compared with CDX2 alone, dual positive expression for SATB2 and CDX2 (SATB2(+)/CDX2(+)) has a significantly higher specificity for adenocarcinoma of lower GI tract origin (94% vs. 57%, P < 0.001). In colorectal carcinoma, loss of SATB2 expression was more frequently observed in DNA mismatch repair (MMR) protein deficient tumors (31%) compared with MMR protein proficient tumors (13%) (P < 0.01). A BRAF V600E mutation was more frequently identified in colorectal carcinomas with loss of SATB2 expression compared with those with positive SATB2 expression (29% vs. 3%) (P < 0.001). In summary, SATB2 expression is a relatively specific marker of lower GI tract origin; however, loss of SATB2 expression is more commonly seen in colorectal carcinoma with MMR protein deficiency and BRAF mutation.