Alternative titles; symbols
HGNC Approved Gene Symbol: FZD4
SNOMEDCT: 415297005; ICD10CM: H35.1, H35.10, H35.17; ICD9CM: 362.20, 362.21;
Cytogenetic location: 11q14.2 Genomic coordinates (GRCh38) : 11:86,945,679-86,955,395 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 11q14.2 | Exudative vitreoretinopathy 1 | 133780 | Autosomal dominant | 3 |
| Retinopathy of prematurity | 133780 | Autosomal dominant | 3 |
Members of the 'frizzled' (FZ) gene family (see 606143) encode 7-transmembrane domain proteins that are receptors for Wnt (see Wnt5A; 164975) signaling proteins.
By screening a human fetal lung cDNA library with an FZD4 cDNA fragment isolated from a human gastric cancer cDNA pool, Kirikoshi et al. (1999) obtained a full-length cDNA of FZD4. FZD4 encodes a deduced 537-amino acid protein that has a cysteine-rich domain (CRD) in the N-terminal extracellular region, 2 cysteine residues in the second and third extracellular loops, 2 extracellular N-linked glycosylation sites, and the S/T-X-V motif in the C terminus. Amino acid sequence identity with other FZD proteins ranged from 39 to 52% in the N terminus to 42 to 69% in the transmembrane domains. Northern blot analysis revealed expression of a 7.7-kb transcript in large amounts in adult heart, skeletal muscle, ovary, and fetal kidney, in moderate amounts in adult liver, kidney, pancreas, spleen, and fetal lung, and in small amounts in placenta, adult lung, prostate, testis, colon, fetal brain, and liver. Expression was also strong in HeLa cells but not in several cancer cell lines.
By screening a fetal lung cDNA library using the C terminus of FZD4 as probe, followed by PCR of a fetal kidney cDNA library, Sagara et al. (2001) cloned an FZD4 variant, which they called FZD4S. FZD4S is unspliced and includes exon 1, intron 1, and exon 2. The deduced protein contains only 125 amino acids due to the introduction of a stop codon within the retained intron. The N-terminal 98 amino acids of FZD4S are identical to those of the full-length FZD4 protein, but the last 27 residues are unique. Compared with FZD4, FZD4S retains the N-terminal signal peptide and the N-terminal part of the CRD, but not the latter half of the CRD or the 7 transmembrane domains, indicating that FZD4S is likely to be a soluble protein. Northern blot analysis detected modest expression of a 10.0-kb mRNA in fetal kidney and faint expression in adult heart and fetal lung. RNA dot blot analysis detected expression in adult heart and lung and in fetal kidney and lung.
Sagara et al. (2001) injected synthetic FZD4S mRNA into the ventral marginal zone of Xenopus embryos at the 4-cell stage. The injected FZD4S did not induce axis duplication by itself, but augmented the axis duplication potential of coinjected Xenopus Wnt8 (see 601396) mRNA. Sagara et al. (2001) concluded that the FZD4S variant of FZD4 is a soluble protein that can activate the WNT signaling pathway.
The findings of Robitaille et al. (2002) supported a function for FZD4 in retinal angiogenesis. Robitaille et al. (2002) injected Xenopus laevis embryos with wildtype and familial exudative vitreoretinopathy (FEVR; 133780)-associated FZD4 mutants. They found that wildtype FZD4, but not mutant FZD4, activated CAMK2 (see 114078) and PKC (see 176960), components of the Wnt/Ca(2+) signaling pathway.
Chen et al. (2003) found that endocytosis of FZD4 in human embryonic kidney cells was dependent on added WNT5A protein and was accomplished by the multifunctional adaptor protein beta-arrestin-2 (107941), which was recruited to FZD4 by binding to phosphorylated dishevelled-2 (DVL2; 602151). The authors concluded that their findings provided a previously unrecognized mechanism for receptor recruitment of beta-arrestin and demonstrated that dishevelled plays an important role in the endocytosis of frizzled, as well as in promoting signaling.
Using a complementation assay, Kaykas et al. (2004) found that FZD4 could form homodimers. It could also form heterodimers with other FZD proteins, including rat Fzd1 (603408), rat Fzd2 (600667), Xenopus Fzd7 (603410), and human FZD9 (601766). Strongest affinity was displayed by proteins with similar amino acid sequence. Kaykas et al. (2004) found that an FEVR-associated FZD4 mutant with a frameshift at leu501 (604579.0002), which does not accumulate at the plasma membrane, was trapped in the endoplasmic reticulum. Through heterodimerization, this mutant FZD4 could trap wildtype FZD4 and inhibit its signaling.
Incomplete retinal vascularization occurs in both Norrie disease (310600) and FEVR. Norrin, the protein product of the NDP gene (300658), is a secreted protein. One form of FEVR is caused by defects in FZD4, a presumptive Wnt receptor. Xu et al. (2004) determined that norrin and FZD4 function as a ligand-receptor pair based on the similarity in vascular phenotypes caused by norrin and FZD4 mutations in humans and mice; the specificity and high affinity of norrin-FZD4 binding; the high efficiency with which norrin induces FZD4- and LRP (see 107770)-dependent activation of the classical Wnt pathway; and the signaling defects displayed by disease-associated variants of norrin and FZD4. These data defined a norrin-FZD4 signaling system that plays a central role in vascular development in the eye and ear, and they indicated that ligands unrelated to Wnts can act through frizzled receptors.
Using yeast 2-hybrid assays, Yao et al. (2004) found that PDZ domain 1 of mouse Magi3 (615943) interacted with the C-terminal PDZ-binding motifs of Fzd4 and Fzd7. PDZ domain 1 also interacted with Ltap (VANGL2; 600533), another planar cell polarity signaling protein. Magi3, Fzd4, and Ltap independently localized to sites of cell-cell contacts in epithelial cells, and these 3 proteins interacted in a complex that required Magi3. Magi3 strongly enhanced Rac (see 602048)-dependent Jnk (see 601158) activation by Fzd4 and Ltap.
Kirikoshi et al. (1999) determined that the FZD4 gene contains 2 exons.
Crystal Structure
Yang et al. (2018) presented the atomic-resolution structure of the human FZD4 transmembrane domain in the absence of a bound ligand. The structure revealed an unusual transmembrane architecture in which helix VI is short and tightly packed, and is distinct from all other GPCR structures reported so far. Within this unique transmembrane fold is an extremely narrow and highly hydrophilic pocket that is not amenable to the binding of traditional GPCR ligands. Yang et al. (2018) showed that such a pocket is conserved across all FZDs, which may explain the long-standing difficulties in the development of ligands for these receptors. Molecular dynamics simulations on the microsecond timescale and mutational analysis uncovered 2 coupled, dynamic kinks located at helix VII that are involved in FZD4 activation. The stability of the structure in its ligand-free form, an unfavorable pocket for ligand binding, and the 2 unusual kinks on helix VII suggested that FZDs may have evolved a novel ligand recognition and activation mechanism that is distinct from that of other GPCRs.
By FISH, Kirikoshi et al. (1999) mapped the FZD4 gene to chromosome 11q14-q21. By positional cloning, Robitaille et al. (2002) mapped the FZD4 gene to chromosome 11q14.2.
In affected members of 2 unrelated families with autosomal dominant familial exudative vitreoretinopathy (EVR1; 133780), Robitaille et al. (2002) identified 2 different heterozygous deletions in exon 2 of the FZD4 gene (604579.0001; 604579.0002). Both mutations altered the seventh transmembrane domain and the intracellular carboxy-terminal tail, respectively. No mutations in FZD4 were detected in 3 other small families with FEVR. Robitaille et al. (2002) presented data indicating that the changes in FZD4 in these families with autosomal dominant FEVR represented loss-of-function mutations. Following transfection in COS-7 cells, wildtype FZD4 and the FEVR-related FZD4 mutant lacking met493 and trp494 accumulated at the plasma membrane; however, the mutant containing the frameshift at leu501 did not.
In an infant with advanced retinopathy of prematurity (see 133780), MacDonald et al. (2005) identified heterozygosity for a missense mutation in the FZD4 gene (604579.0006).
Using a norrin-based reporter assay to analyze the effects of FEVR-causing mutations, Qin et al. (2008) demonstrated that a nonsense mutation in FZD4 completely abolished signaling activity, whereas missense mutations in FZD4 and LRP5 (603506) caused a moderate level of reduction, and a double missense mutation in both genes caused a severe reduction in activity, correlating roughly with clinical phenotypes. Norrin mutants, however, showed variable effects on signal transduction, and no correlation with clinical phenotypes was observed; norrin mutants also showed impaired cell surface binding. Qin et al. (2008) concluded that norrin signaling is involved in FEVR pathogenesis, but suggested the presence of an unknown parallel pathway at the level of receptor/ligand binding as evidenced by the moderate and variable signal reduction lacking a clear genotype/phenotype correlation.
In a large Canadian kindred of British descent with exudative vitreoretinopathy (EVR1; 133780), Robitaille et al. (2002) demonstrated that affected members had a mutation in the FZD4 gene: deletion of nucleotides 1479-1484, resulting in deletion of 2 highly conserved amino acids, met493 and trp494.
In a family of European descent with exudative vitreoretinopathy (EVR1; 133780), Robitaille et al. (2002) demonstrated that affected members carried a 2-bp deletion in the FZD4 gene, resulting in frameshift at leu501, creating a stop codon at residue 533.
In patients with exudative vitreoretinopathy (EVR1; 133780), Kondo et al. (2003) identified a heterozygous 1250G-A transition in exon 2 of the FZD4 gene, resulting in an arg417-to-gln (R417Q) substitution.
Qin et al. (2005) reported a Japanese family with digenic inheritance of EVR. Affected members had a heterozygous R417Q mutation in the FZD4 gene consistent with EVR1 and a heterozygous mutation in the LRP5 gene (R444C; 603506.0026) consistent with EVR4 (601813). The 2 mutations cosegregated in the family, indicating that both mutations were located on the same chromosome consistent with digenic inheritance. The ocular phenotype in this family tended to be more severe compared to that of the family reported by Kondo et al. (2003) with the FZD4 R417Q mutation alone.
In a Japanese girl with exudative vitreoretinopathy (EVR1; 133780), Yoshida et al. (2004) identified a heterozygous 1026A-G transition in the FZD4 gene, resulting in a met342-to-val (M342V) substitution. She had esotropia and exudative retinal detachment at age 3 years. Her asymptomatic father, who also carried the mutation, was found to have bilateral avascular areas in the peripheral retina.
In a Japanese infant with exudative vitreoretinopathy (EVR1; 133780) and bilateral retinal folds, Qin et al. (2005) identified a heterozygous 1005G-C transversion in exon 2 of the FZD4 gene, resulting in a trp335-to-cys (W335C) substitution. The child's asymptomatic mother, who also carried the mutation, exhibited bilateral peripheral retinal avascularization with vascular tortuosity.
In an infant with advanced retinopathy of prematurity (see 133780), MacDonald et al. (2005) identified heterozygosity for a 766A-G transition in the FZD4 gene, resulting in an ile256-to-val (I256V) substitution. The mutation was not observed in 200 normal chromosomes.
Chen, W., ten Berge, D., Brown, J., Ahn, S., Hu, L. A., Miller, W. E., Caron, M. G., Barak, L. S., Nusse, R., Lefkowitz, R. J. Dishevelled 2 recruits beta-arrestin 2 to mediate Wnt5A-stimulated endocytosis of frizzled 4. Science 301: 1391-1394, 2003. [PubMed: 12958364] [Full Text: https://doi.org/10.1126/science.1082808]
Kaykas, A., Yang-Snyder, J., Heroux, M., Shah, K. V., Bouvier, M., Moon, R. T. Mutant frizzled 4 associated with vitreoretinopathy traps wild-type frizzled in the endoplasmic reticulum by oligomerization. Nature Cell Biol. 6: 52-58, 2004. [PubMed: 14688793] [Full Text: https://doi.org/10.1038/ncb1081]
Kirikoshi, H., Sagara, N., Koike, J., Tanaka, K., Sekihara, H., Hirai, M., Katoh, M. Molecular cloning and characterization of human frizzled-4 on chromosome 11q14-q21. Biochem. Biophys. Res. Commun. 264: 955-961, 1999. [PubMed: 10544037] [Full Text: https://doi.org/10.1006/bbrc.1999.1612]
Kondo, H., Hayashi, H., Oshima, K., Tahira, T., Hayashi, K. Frizzled 4 gene (FZD4) mutations in patients with familial exudative vitreoretinopathy with variable expressivity. Brit. J. Ophthal. 87: 1291-1295, 2003. [PubMed: 14507768] [Full Text: https://doi.org/10.1136/bjo.87.10.1291]
MacDonald, M. L. E., Goldberg, Y. P., MacFarlane, J., Samuels, M. E., Trese, M. T., Shastry, B. S. Genetic variants of frizzled-4 gene in familial exudative vitreoretinopathy and advanced retinopathy of prematurity. (Letter) Clin. Genet. 67: 363-366, 2005. [PubMed: 15733276] [Full Text: https://doi.org/10.1111/j.1399-0004.2005.00408.x]
Qin, M., Hayashi, H., Oshima, K., Tahira, T., Hayashi, K., Kondo, H. Complexity of the genotype-phenotype correlation in familial exudative vitreoretinopathy with mutations in the LRP5 and/or FZD4 genes. Hum. Mutat. 26: 104-112, 2005. [PubMed: 15981244] [Full Text: https://doi.org/10.1002/humu.20191]
Qin, M., Kondo, H., Tahira, T., Hayashi, K. Moderate reduction of Norrin signaling activity associated with the causative missense mutations identified in patients with familial exudative vitreoretinopathy. Hum. Genet. 122: 615-623, 2008. [PubMed: 17955262] [Full Text: https://doi.org/10.1007/s00439-007-0438-8]
Robitaille, J., MacDonald, M. L. E., Kaykas, A., Sheldahl, L. C., Zeisler, J., Dube, M.-P., Zhang, L.-H., Singaraja, R. R., Guernsey, D. L., Zhang, B., Siebert, L. F., Hoskin-Mott, A., Trese, M. T., Pimstone, S. N., Shastry, B. S., Moon, R. T., Hayden, M. R., Goldberg, Y. P., Samuels, M. E. Mutant frizzled-4 disrupts retinal angiogenesis in familial exudative vitreoretinopathy. Nature Genet. 32: 326-330, 2002. [PubMed: 12172548] [Full Text: https://doi.org/10.1038/ng957]
Sagara, N., Kirikoshi, H., Terasaki, H., Yasuhiko, Y., Toda, G., Shiokawa, K., Katoh, M. FZD4S, a splicing variant of frizzled-4, encodes a soluble-type positive regulator of the WNT signaling pathway. Biochem. Biophys. Res. Commun. 282: 750-756, 2001. [PubMed: 11401527] [Full Text: https://doi.org/10.1006/bbrc.2001.4634]
Xu, Q., Wang, Y., Dabdoub, A., Smallwood, P. M., Williams, J., Woods, C., Kelley, M. W., Jiang, L., Tasman, W., Zhang, K., Nathans, J. Vascular development in the retina and inner ear: control by norrin and frizzled-4, a high-affinity ligand-receptor pair. Cell 116: 883-895, 2004. [PubMed: 15035989] [Full Text: https://doi.org/10.1016/s0092-8674(04)00216-8]
Yang, S., Wu, Y., Xu, T.-H., de Waal, P. W., He, Y., Pu, M., Chen, Y., DeBruine, Z. J., Zhang, B., Zaidi, S. A., Popov, P., Guo, Y., and 13 others. Crystal structure of the Frizzled 4 receptor in a ligand-free state. Nature 560: 666-670, 2018. [PubMed: 30135577] [Full Text: https://doi.org/10.1038/s41586-018-0447-x]
Yao, R., Natsume, Y., Noda, T. MAGI-3 is involved in the regulation of the JNK signaling pathway as a scaffold protein for frizzled and Ltap. Oncogene 23: 6023-6030, 2004. [PubMed: 15195140] [Full Text: https://doi.org/10.1038/sj.onc.1207817]
Yoshida, S., Arita, R.-I., Yoshida, A., Tada, H., Emori, A., Noda, Y., Nakao, S., Fujisawa, K., Ishibashi, T. Novel mutation in FZD4 gene in a Japanese pedigree with familial exudative vitreoretinopathy. Am. J. Ophthal. 138: 670-671, 2004. [PubMed: 15488808] [Full Text: https://doi.org/10.1016/j.ajo.2004.05.001]