Characterization of the Complete Genomic Structure of the Human WNT-5A Gene, Functional Analysis of its Promoter, Chromosomal Mapping, and Expression in Early Human Embryogenesis

Abstract

We report the complete genomic organization of the human WNT-5A gene, which encodes a cysteine-rich growth factor involved in cell-cell signaling during growth and differentiation. The gene comprises five exons with the terminal exon coding for a large 3-untranslated region of Ϸ6.5 kilobase pairs and utilizes multiple polyadenylation signals to generate at least four discrete transcripts. We discovered a new leader exon interrupted by a 411-base pair intron that was retained in our original cDNA cloning. The promoter region was located in a GpC-rich island and harbored numerous cis-acting elements including several GC boxes and Sp1, AP1, and AP2 binding motifs. It lacked TATA or CAAT boxes typical of housekeeping and growth factor genes. In support of this, primer extension revealed two transcription start sites. Transient cell transfection assays showed functional promoter activity for the 3.9-kilobase pair 5-flanking region. Interestingly, internal and 5 deletions revealed that the distal promoter was not required for full transcriptional activity and that the first 631 base pairs of WNT-5A harbored the strongest promoter activity. Using a panel of rodent-human hybrid DNAs carrying portions of chromosome 3p, we mapped the gene to 3p14.2-p21.1, between a constitutional and a familial renal cell carcinoma-associated translocation. In situ hybridization analyses of early human embryos at 28 -42 days of gestation revealed that WNT-5A transcripts were not restricted to the developing brain and limbs but were also observed in the mesenchyme bordering the pharyngeal clefts and pouches and in the developing gonads and kidneys. The relatively high expression in the celomic epithelium and in the precursors of follicles and seminiferous tubules suggest a novel role for WNT-5A in germ-cell differentiation. This study provides the molecular basis for discerning the regulation of the WNT-5A gene and offers the opportunity to investigate genetic disorders linked to this important gene.

Increased Expression of Colonic Wnt9A through Sp1-mediated Transcriptional Effects involving Arylsulfatase B, Chondroitin 4-Sulfate, and Galectin-3

“…Future studies will clarify whether or not the interactions of ARSB, C4S, and galectin-3 also influence effects of Sp3 or Sp4 on Wnt9A transcription, or on transcription of other Wnt family members, in colonic epithelium and in other tissues. Sp1 has also been associated with activation of WNT5A, both in human embryonic tissues and in airway smooth muscle cells following stimulation by TGF-␤ (60,61).…”

Transcriptional mechanisms of WNT5A based on NF-κB, Hedgehog, TGFβ, and Notch signaling cascades

“…The WNT5A gene at human chromosome 3p14.3 (7,8) is the paralog of the WNT5B gene at human chromosome 12p13.33 (9). Human WNT5A shows 98.7% total amino-acid identity with rodent Wnt5a (10,11), indicating that mammalian WNT5A orthologs are ultra-conserved.…”

Canonical and noncanonical Wnt pathway: A comparison among normal ovary, benign ovarian tumor and ovarian cancer

“…It encodes a protein involved in cell-cell signaling during embryonic development (9)(10)(11)(12)(13) (14). Thereby, some authors affirm that the noncanonical pathway would assume an antagonistic effect on the canonical pathway through different mechanisms and the Wnt5a would be a tumor suppressor (15)(16)(17)(18).…”