WISP3, the Gene Responsible for the Human Skeletal Disease Progressive Pseudorheumatoid Dysplasia, Is Not Essential for Skeletal Function in Mice

Abstract

In humans, loss-of-function mutations in WISP3 cause the autosomal recessive skeletal disease progressive pseudorheumatoid dysplasia (PPD) (Online Mendelian Inheritance in Man database number 208230). WISP3 encodes Wnt1-inducible signaling protein 3, a cysteine-rich, multidomain, secreted protein, whose paralogous CCN (connective tissue growth factor/cysteine-rich protein 61/nephroblastoma overexpressed) family members have been implicated in diverse biologic processes including skeletal, vascular, and neural development. To understand the role of WISP3 in the skeleton, we targeted the Wisp3 gene in mice by creating a mutant allele comparable to that which causes human disease. We also created transgenic mice that overexpress human WISP3 in cartilage. Surprisingly, homozygous Wisp3 mutant mice appear normal and do not recapitulate any of the morphological, radiographic, or histological abnormalities seen in patients with PPD. Mice that overexpress WISP3 are also normal. We conclude, that in contrast to humans, Wisp3 is not an essential participant during skeletal growth or homeostasis in mice.The CCN (connective tissue growth factor/cysteine-rich protein 61/nephroblastoma overexpressed) protein family comprises six cysteine-rich, multidomain-containing, secreted proteins (1,19,20). To date, only one CCN family member, Wnt1-inducible signaling protein 3 (WISP3/CCN6) has been associated with a human genetic disease. Mutations in WISP3 cause progressive pseudorheumatoid dysplasia (PPD) (4, 8), an autosomal recessive form of a spondyloepiphyseal dysplasia tarda. Individuals with PPD appear normal at birth, have subtle clinical symptoms by 3 years of age, manifest radiologic changes of the axial and appendicular skeleton by 5 years of age, and develop severe degenerative joint disease necessitating joint replacement surgery by their second decade of life (5,21,24,27). Radiologically, in addition to platyspondyly, young patients with PPD have multiple sites of epiphyseal enlargement compared to age-and gender-matched controls (12,17). Histological examination shows that articular cartilage retrieved at the time of joint replacement surgery from patients with PPD is indistinguishable from that seen in common endstage osteoarthritis (W. Kutz et al., unpublished data). Individuals with PPD have no organ involvement outside of their skeletal system. Consequently, in humans, the principal role of WISP3 appears to involve skeletal growth and cartilage homeostasis.We disrupted the Wisp3 gene in mice to create an animal model of Wisp3 deficiency and thus delineate the precise role of this protein in the skeleton. We found that homozygous Wisp3 mutant (Wisp3 Ϫ/Ϫ ) mice do not recapitulate any of the features that have been observed in patients with PPD. We also created transgenic mice that overexpress human WISP3 in cartilage; these mice are also normal. Our results suggest that although WISP3 is critical for normal skeletal function in humans, Wisp3 is not essential in mice. MATERIALS AND METHODS Construction of the Wisp3 tar...

The CCN family member Wisp3, mutant in progressive pseudorheumatoid dysplasia, modulates BMP and Wnt signaling

“…While zwisp3 mRNA was detected by in situ hybridization at 24 hpf, zWisp3 protein expression was detected by Western blot at 48 hpf ( Figure 2E). These results also contrast with previous studies in mice in which endogenous mWisp3 protein was undetectable prenatally and postnatally (27).…”

“…Expression of zwisp3 was also observed in the swim bladder at 96 hpf and persisted in this structure until at least 168 hpf ( Figure 2, C and D). These results contrast with previous studies in humans and mice in which mRNA expression was only detected by RT-PCR (1,10,27). While zwisp3 mRNA was detected by in situ hybridization at 24 hpf, zWisp3 protein expression was detected by Western blot at 48 hpf ( Figure 2E).…”

All in the CCN family: essential matricellular signaling modulators emerge from the bunker

“…Conversely, mice in which exons III, IV and V of CCN6 were deleted, resulting in absence of CCN6 expression, showed no apparent phenotype (Kutz et al, 2005). In this study CCN6 expression was not detected anywhere in the mouse (Kutz et al, 2005). Although it is possible that complete loss of CCN6 expression in ccn6 -/-mice may have resulted in the compensatory overexpression of other CCN family members, it is also plausible that additional factors than CCN6 may be the cause of PPD.…”

“…Point mutations in CCN6 have been linked to the autosomal recessive skeletal disease progressive pseudorheumatoid dysplasia (PPD), a human disease (Hurvitz et al, 1999), resulting in juvenile-onset cartilage degeneration. Conversely, mice in which exons III, IV and V of CCN6 were deleted, resulting in absence of CCN6 expression, showed no apparent phenotype (Kutz et al, 2005). In this study CCN6 expression was not detected anywhere in the mouse (Kutz et al, 2005).…”

The CCN family of genes: a perspective on CCN biology and therapeutic potential

“…Transgenic mouse models, in vitro cell line models, and generation of domain and isoform specific antibodies constitute a rich source of tools for the studies. Knockout mouse models of CCN have uncovered a broader role for CCN proteins in normal and pathological processes [Kawaki et al 2008;Heath et al 2008;Canalis 2007;Kuiper et al 2007;Kutz et al 2005;Ivkovic et al 2003;Brigstock 2002]. Cell line models, especially those capable of transitioning developmental states, like stem cells, are proving effective in exploring phenotype/function relationships [Katsuki et al 2008;Schutze et al 2007;Djoua et al 2007;Si et al 2006].…”