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Molecular cloning, gene structure, and expression analyses of NKD1 and NKD2
1Genetics and Cell Biology Section, Genetics Division, National Cancer Center Research Institute, Tokyo 104-0045, Japan. mkatoh@ncc.go.jp
Abstract:
Mouse Nkd is a Dishevelled-binding protein, functioning as a negative regulator of WNT - beta-catenin - TCF signaling pathway. Here, human NKD1 and NKD2 were cloned and characterized. NKD1 and NKD2 were predicted to encode 470- and 451-amino-acid polypeptide, respectively. NKD1 and NKD2, showing 43.8% total amino-acid identity, were more homologous in the NH1, NH2, NH3, and NH4 domains. The NH2 domain of NKD1 and NKD2 contained the EF-hand motif. Exon-intron structures of NKD1 and NKD2 genes, consisting of 10 exons, were well conserved. NKD1 was highly expressed in fetal kidney, while NKD2 was moderately expressed in fetal kidney, lung, and adult lung. NKD1 was up-regulated in colorectal cancer cell line SW480, gastric cancer cell line TMK1, and pancreatic cancer cell line Hs700T. NKD2 was up-regulated in gastric cancer cell line MKN45, pancreatic cancer cell line BxPC-3, and esophageal cancer cell lines TE6, and TE13. NKD1 and NKD2 were up-regulated together in 1 case of primary gastric cancer out of 10 cases, and were down-regulated together in 2 cases. Up-regulation of NKD1 or NKD2 might be due to a negative feed-back mechanism. Alternatively, genetic alteration of NKD1 or NKD2 might lead to activation of the WNT - beta-catenin - TCF signaling pathway.
Insights
Human NKD1 and NKD2 proteins, negative regulators of the WNT signaling pathway, were cloned and characterized. Their differential expression in fetal tissues and up-regulation in various cancers suggest roles in cancer development.
Area of Science:
- Molecular Biology
- Cancer Research
- Signal Transduction
Background:
- Mouse Nkd acts as a negative regulator of the WNT-beta-catenin-TCF signaling pathway.
- Understanding human NKD1 and NKD2 function is crucial for cancer research.
Purpose of the Study:
- To clone and characterize human NKD1 and NKD2 genes and proteins.
- To investigate the expression patterns of NKD1 and NKD2 in normal tissues and cancer cell lines.
- To explore the potential role of NKD1 and NKD2 in cancer development.
Main Methods:
- Cloning and characterization of human NKD1 and NKD2.
- Prediction of polypeptide sequences and analysis of protein homology.
- Examination of exon-intron structures and conserved domains (NH1-4, EF-hand motif).
- Analysis of gene expression in fetal and adult tissues.
- Assessment of NKD1 and NKD2 expression levels in various cancer cell lines and primary gastric cancer.
Main Results:
- Human NKD1 and NKD2 were predicted to encode 470- and 451-amino-acid polypeptides, respectively, with 43.8% total amino-acid identity.
- Conserved domains (NH1-4) and the EF-hand motif in the NH2 domain were identified.
- NKD1 showed high expression in fetal kidney; NKD2 was moderately expressed in fetal kidney, lung, and adult lung.
- NKD1 and NKD2 were frequently up-regulated in colorectal, gastric, pancreatic, and esophageal cancer cell lines.
- Co-up-regulation and co-down-regulation of NKD1 and NKD2 were observed in primary gastric cancer cases.
Conclusions:
- Human NKD1 and NKD2 share conserved structural features and domains.
- Differential expression patterns suggest tissue-specific roles for NKD1 and NKD2.
- Up-regulation of NKD1 and NKD2 in cancer may indicate a negative feedback mechanism or be linked to WNT pathway activation.