Sorsby fundus dystrophy mutation Timp3(S156C) affects the morphological and biochemical phenotype but not metalloproteinase homeostasis

The tissue inhibitor of metalloproteinases-3 (TIMP3) is a multifunctional protein tightly associated with the extracellular matrix (ECM). A specific type of mutation in TIMP3 which results in potentially unpaired cysteine residues at the C-terminus of the protein has been shown to cause Sorsby fundus dystrophy (SFD), an autosomal dominant retinopathy of late onset. An early finding in SFD is a striking accumulation of protein and lipid material in Bruch's membrane, a multilayered ECM structure located between the choroid and the RPE. To study the molecular mechanisms underlying SFD pathology, we recently generated two mouse lines, one deficient in Timp3 (Timp3(-/-)) and one carrying an SFD-related mutation in the orthologous murine Timp3 gene (Timp3(S156C/S156C)). We now established immortalized fibroblast cells from the mutant mouse strains and provide evidence that the various cell lines display distinct morphological and physiological features that are dependent on the mutational status of the Timp3 protein in the secreted ECM. We show that matrix metalloproteinase (MMP) activity and inhibitory properties of Timp3 are not affected by the SFD-associated mutation. We further demonstrate that Timp3(S156C) protein accumulates in the ECM of the mutant fibroblast cells and that this accumulation is not due to a prolonged turnover rate of mutant vs. normal Timp3. We also show that the relative abundance of mutant and normal Timp3 in the ECM has no measurable effects on cellular phenotypes. Together, these findings suggest (i) a functional role of normal Timp3 in pathways determining cellular morphology and (ii) a loss of this particular function as a consequence of the Ser156Cys mutation. We therefore hypothesize that SFD pathogenesis is due to a loss-of-function mutation in TIMP3.     

Loss of Timp3 Gene Leads to Abdominal Aortic Aneurysm Formation in Response to Angiotensin II

Aortic aneurysm is dilation of the aorta primarily due to degradation of the aortic wall extracellular matrix (ECM). Tissue inhibitors of metalloproteinases (TIMPs) inhibit matrix metalloproteinases (MMPs), the proteases that degrade the ECM. Timp3 is the only ECM-bound Timp, and its levels are altered in the aorta from patients with abdominal aortic aneurysm (AAA). We investigated the causal role of Timp3 in AAA formation. Infusion of angiotensin II (Ang II) using micro-osmotic (Alzet) pumps in Timp3^−/− male mice, but not in wild type control mice, led to adverse remodeling of the abdominal aorta, reduced collagen and elastin proteins but not mRNA, and elevated proteolytic activities, suggesting excess protein degradation within 2 weeks that led to formation of AAA by 4 weeks. Intriguingly, despite early up-regulation of MMP2 in Timp3^−/−Ang II aortas, additional deletion of Mmp2 in these mice (Timp3^−/−/Mmp2^−/−) resulted in exacerbated AAA, compromised survival due to aortic rupture, and inflammation in the abdominal aorta. Reconstitution of WT bone marrow in Timp3^−/−/Mmp2^−/− mice reduced inflammation and prevented AAA in these animals following Ang II infusion. Treatment with a broad spectrum MMP inhibitor (PD166793) prevented the Ang II-induced AAA in Timp3^−/− and Timp3^−/−/Mmp2^−/− mice. Our study demonstrates that the regulatory function of TIMP3 is critical in preventing adverse vascular remodeling and AAA. Hence, replenishing TIMP3, a physiological inhibitor of a number of metalloproteinases, could serve as a therapeutic approach in limiting AAA development or expansion.     

Sorsby's fundus dystrophy tissue inhibitor of metalloproteinases-3 (TIMP-3) mutants have unimpaired matrix metalloproteinase inhibitory activities, but affect cell adhesion to the extracellular matrix.

The TIMP family of matrix metalloproteinase inhibitors consists of four members, of which TIMP-1, -2 and -4 are secreted, freely diffusible proteins, whereas TIMP-3 is ECM-associated. Mutations in the TIMP3 gene have been linked to Sorsby's fundus dystrophy (SFD), an autosomal dominant inherited retinal degenerative disease that leads to blindness. The SFD mutations characterized result in introduction of an unpaired cysteine residue in the C-terminal domain of TIMP-3. We have expressed four SFD mutant TIMP-3 proteins in baby hamster kidney (BHK) cells and evaluated their characteristics alongside wild-type TIMP-3. Analysis of the mutant proteins (Ser156Cys, Gly167Cys, Tyr168Cys and Ser181Cys) by SDS-PAGE and reverse zymography revealed that each of the mutants retained gelatinase A and gelatinase B inhibitory activity, and were localized to the ECM. Association rate constants for Ser156Cys TIMP-3 with gelatinase-A, gelatinase-B, stromelysin-1 and collagenase-3 were only moderately reduced compared to wild-type TIMP-3. However, all of the mutants displayed aberrant protein-protein interactions, resulting in the presence of additional proteins or complexes in ECM preparations. Two of the mutants (Ser156Cys and Ser181Cys) showed a marked propensity to form multiple higher molecular-weight complexes that retained TIMP activity on reverse zymography. Expression of the SFD mutant TIMP-3 (and to a lesser extent, wild-type TIMP-3) proteins in BHK cells conferred increased cell adhesiveness to the ECM. Our findings indicate that the pathogenesis of Sorsby's fundus dystrophy cannot be attributed to a failure to localize SFD TIMP-3 proteins to the ECM or defects in MMP inhibition, but may involve the formation of aberrant TIMP-3-containing protein complexes and altered cell adhesion.     

Mice with Tissue Inhibitor of Metalloproteinases 4 (Timp4) Deletion Succumb to Induced Myocardial Infarction but Not to Cardiac Pressure Overload

Tissue inhibitor of metalloproteinases 4 (TIMP4) is expressed highly in heart and found dysregulated in human cardiovascular diseases. It controls extracellular matrix remodeling by inhibiting matrix metalloproteinases (MMPs) and is implicated in processes including cell proliferation, apoptosis, and angiogenesis. Timp4-deficient mice (Timp4^−/−) were generated to assess TIMP4 function in normal development and in models of heart disease. We deleted exons 1–3 of the Timp4 gene by homologous recombination. Timp4^−/− mice are born healthy, develop normally, and produce litters of normal size and gender distribution. These mice show no compensation by overexpression of Timp1, Timp2, or Timp3 in the heart. Following cardiac pressure overload by aortic banding, Timp4^−/− mice have comparable survival rate, cardiac histology, and cardiac function to controls. In this case, Timp4 deficiency is compensated by increased cardiac Timp2 expression. Strikingly, the induction of myocardial infarction (MI) leads to significantly increased mortality in Timp4^−/− mice primarily due to left ventricular rupture. The post-MI mortality of Timp4^−/− mice is reduced by administration of a synthetic MMP inhibitor. Furthermore, combining the genetic deletion of Mmp2 also rescues the higher post-MI mortality of Timp4^−/− mice. Finally, Timp4^−/− mice suffer reduced cardiac function at 20 months of age. Timp4 is not essential for murine development, although its loss moderately compromises cardiac function with aging. Timp4^−/− mice are more susceptible to MI but not to pressure overload, and TIMP4 functions in its capacity as a metalloproteinase inhibitor after myocardial infarction.     

Drosophila TIMP is a potent inhibitor of MMPs and TACE: similarities in structure and function to TIMP-3

The four tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors that regulate the activity of matrix metalloproteinases (MMPs) and certain disintegrin and metalloproteinase (ADAM) family proteases in mammals. The protease inhibitory activity is present in the N-terminal domains of TIMPs (N-TIMPs). In this work, the N-terminal inhibitory domain of the only TIMP produced by Drosophila (dN-TIMP) was expressed in Escherichia coli and folded in vitro. The purified recombinant protein is a potent inhibitor of human MMPs, including membrane-type 1-MMP, although it lacks a disulfide bond that is conserved in all other known N-TIMPs. Titration with the catalytic domain of human MMP-3 [MMP-3(DeltaC)] showed that dN-TIMP prepared by this method is correctly folded and fully active. dN-TIMP also inhibits, in vitro, the activity of the only two MMPs of Drosophila, dm1- and dm2-MMPs, indicating that the Drosophila TIMP is an endogenous inhibitor of the Drosophila MMPs. dN-TIMP resembles mammalian N-TIMP-3 in strongly inhibiting human tumor necrosis factor-alpha-converting enzyme (TACE/ADAM17) but is a weak inhibitor of human ADAM10. Models of the structures of dN-TIMP and N-TIMP-3 are strikingly similar in surface charge distribution, which may explain their functional similarity. Although the gene duplication events that led to the evolutionary development of the four mammalian TIMPs might be expected to be associated with functional specialization, Timp-3 appears to have conserved most of the functions of the ancestral TIMP gene.     

Threonine 98, the pivotal residue of tissue inhibitor of metalloproteinases (TIMP)-1 in metalloproteinase recognition

Tissue inhibitors of metalloproteinases (TIMPs) are the endogenous modulators of the zinc-dependent mammalian matrix metalloproteinases (MMPs) and their close associates, proteinases of the ADAM (a disintegrin and metalloproteinase) and ADAM with thrombospondin repeats families. There are four variants of TIMPs, and each has its defined set of metalloproteinase (MP) targets. TIMP-1, in particular, is inactive against several of the membrane-type MMPs (MT-MMPs), MMP-19, and the ADAM proteinase TACE (tumor necrosis factor-alpha-converting enzyme, ADAM-17). The molecular basis for such inactivity is unknown. Previously, we showed that TIMP-1 could be transformed into an active inhibitor against MT1-MMP by the replacement of threonine 98 residue with leucine (T98L). Here, we reveal that the T98L mutation has in fact transformed TIMP-1 into a versatile inhibitor against an array of MPs otherwise insensitive to wild-type TIMP-1; examples include TACE, MMP-19, and MT5-MMP. Using T98L as the scaffold, we created a TIMP-1 variant that is fully active against TACE. The binding affinity of the mutant (V4S/TIMP-3-AB-loop/V69L/T98L) (K (app)(i) 0.14 nm) surpassed that of TIMP-3 (K (app)(i) 0.22 nm), the only natural TIMP inhibitor of the enzyme. The requirement for leucine is absolute for the transformation in inhibitory pattern. On the other hand, the mutation has minimal impact on the MPs already well inhibited by wild-type TIMP-1, such as gelatinase-A and stromelysin-1. Not only have we unlocked the molecular basis for the inactivity of TIMP-1 against several of the MPs, but also our findings fundamentally modify the current beliefs on the molecular mechanism of TIMP-MP recognition and selectivity.     

Structural determinants of the ADAM inhibition by TIMP-3: crystal structure of the TACE-N-TIMP-3 complex

TIMP-3 (tissue inhibitor of metalloproteinases 3) is unique among the TIMP inhibitors, in that it effectively inhibits the TNF-α converting enzyme (TACE). In order to understand this selective capability of inhibition, we crystallized the complex formed by the catalytic domain of recombinant human TACE and the N-terminal domain of TIMP-3 (N-TIMP-3), and determined its molecular structure with X-ray data to 2.3 Å resolution. The structure reveals that TIMP-3 exhibits a fold similar to those of TIMP-1 and TIMP-2, and interacts through its functional binding edge, which consists of the N-terminal segment and other loops, with the active-site cleft of TACE in a manner similar to that of matrix metalloproteinases (MMPs). Therefore, the mechanism of TIMP-3 binding toward TACE is not fundamentally different from that previously elucidated for the MMPs. The Phe34 phenyl side chain situated at the tip of the relatively short sA-sB loop of TIMP-3 extends into a unique hydrophobic groove of the TACE surface, and two Leu residues in the adjacent sC-connector and sE-sF loops are tightly packed in the interface allowing favourable interactions, in agreement with predictions obtained by systematic mutations by Gillian Murphy's group. The combination of favourable functional epitopes together with a considerable flexibility renders TIMP-3 an efficient TACE inhibitor. This structure might provide means to design more efficient TIMP inhibitors of TACE.     

A biochemical model of matrix metalloproteinase 9 activation and inhibition

Matrix metalloproteinases (MMPs) are a class of extracellular and membrane-bound proteases involved in an array of physiological processes, including angiogenesis. We present a detailed computational model of MMP9 activation and inhibition. Our model is validated to existing biochemical experimental data. We determine kinetic rate constants for the processes of MMP9 activation by MMP3, MMP10, MMP13, and trypsin; inhibition by the tissue inhibitors of metalloproteinases (TIMPs) 1 and 2; and MMP9 deactivation. This computational approach allows us to investigate discrepancies in our understanding of the interaction of MMP9 with TIMP1. Specifically, we find that inhibition due to a single binding event cannot describe MMP9 inhibition by TIMP1. Temporally accurate biphasic inhibition requires either an additional isomerization step or a second lower affinity isoform of MMP9. We also theoretically characterize the MMP3/TIMP2/pro-MMP9 and MMP3/TIMP1/pro-MMP9 systems. We speculate that these systems differ significantly in their time scales of activation and inhibition such that MMP9 is able to temporarily overshoot its final equilibrium value in the latter. Our numerical simulations suggest that the ability of pro-MMP9 to complex TIMP1 increases this overshoot. In all, our analysis serves as a summary of existing kinetic data for MMP9 and a foundation for future models utilizing MMP9 or other MMPs under physiologically well defined microenvironments.     

Effect of a coat color locus on kidney lysosomal glycosidases in the house mouse

Activities of three lysosomal glycosidases, -galactosidase, -glucuronidase, and N-acetyl--hexosaminidase, have been shown to differ in bf/bf and bf/+ mice. Thus bf/bf mice usually have much higher activities of these enzymes in their kidney cells than bf/+ animals. There seem, however, to be some exceptions to this general pattern, especially for galactosidase of females from the C57BL/6J strain. A likely interpretation of the difference is that the bf locus has pleiotropic effects. An alternative explanation, less likely, is that a gene closely linked to bf is involved. There is also a differential response to dihydrotestosterone in different groups of mice reflected in activity changes of the three enzymes.This work was supported by the Hierta Memorial Fund and the Swedish Natural Science Research Council.     

A novel splice site mutation in the tissue inhibitor of the metalloproteinases-3 gene in Sorsby’s fundus dystrophy with unusual clinical features

Sorsby’s fundus dystrophy (SFD) is an autosomal dominant macular dystrophy which is developed usually in the third or fourth decade of life, and is characterized by central visual loss and nyctalopia due to fundus changes of exudative or atrophic macular lesions. Its functional prognosis is usually poor because of disciform macular scars and peripheral chorioretinal atrophies. To date, five different mutations in the tissue inhibitor of the metallo-proteinases-3 (TIMP3) gene have been identified in families of a wide geographic origin, all of which are missense mutations that cause replacement by cysteine of conserved amino acids in the C-terminus of exon 5 of TIMP3. We have studied two Japanese families with SFD, the first report from the Eastern world, and identified a novel 3’ splice site mutation in the TIMP3 gene, namely a single base insertion at the intron 4/exon 5 junction which converts the consensus sequence CAG to CAAG in the splice acceptor site. In addition, our patients displayed a distinctive clinical expression in that they developed macular dystrophies at an approximately 30-year later age of onset and preserved functional vision until later life with essentially uninvolved peripheral retina. The present findings may provide some insight into the genotype–phenotype relationship in SFD. Received: 27 March 1998 / Accepted: 2 May 1998     

Interleukin-4 antagonizes oncostatin M and transforming growth factor beta-induced responses in articular chondrocytes

Oncostatin M (OSM) stimulates cartilage degradation in rheumatoid arthritis (RA) by inducing matrix metalloproteinases (MMPs) and aggrecanases (ADAMTS; a disintegrin and metalloproteinase with thrombospondin motif). Transforming growth factor beta (TGF-beta1) induces cartilage repair in joints but in excessive amounts, promotes inflammation. OSM and TGF-beta1 also induce tissue inhibitor of metalloproteinase-3 (TIMP-3), an important natural inhibitor of MMPs, aggrecanases, and tumor necrosis factor alpha converting enzyme (TACE), the principal proteases involved in arthritic inflammation and cartilage degradation. We studied cartilage protective mechanisms of the antiinflammatory cytokine, interleukin-4 (IL-4). IL-4 strongly (MMP-13 and TIMP-3) or minimally (ADAMTS-4) suppressed OSM-induced gene expression in chondrocytes. IL-4 did not affect OSM-stimulated phosphorylation of extracellular signal-regulated kinases (ERKs), protein 38 (p38), c-Jun N-terminal kinase (JNK) and Stat1. Lack of additional suppression with their inhibitors suggested that MMP-13, ADAMTS-4, and TIMP-3 inhibition was independent of these mediators. IL-4 also downregulated TGF-beta1-induced TIMP-3 gene expression, Smad2, and JNK phosphorylation. Additional suppression of TIMP-3 RNA by JNK inhibitor suggests JNK implication. The cartilage protective effects of IL-4 in animal models of arthritis may be due to its inhibition of MMPs and ADAMTS-4 expression. However, suppression of TIMP-3 suggests caution for using IL-4 as a cartilage protective therapy.     

Kit无义突变致W-3Bao小鼠生殖腺异常及纯合子贫血死亡

W-^3Bao是本研究组通过诱变获得、Kit无义突变的白斑小鼠。突变基因杂合子小鼠腹部、四肢肢端及尾尖白化,其部分精曲小管内无精原细胞。突变纯合子小鼠在胚胎后期色泽苍白、个体矮小,于出生前后死亡;血液学检查发现纯合子小鼠血色素极低且红细胞变大;18.5天胚胎的连续切片可见精曲小管轮廓欠清晰,精原细胞分散分布于睾丸间质,未迁入精曲小管;卵巢结构紊乱,无明显的原始卵泡结构;骨髓等器官组织未见显著异常。结论：Kit无义突变不仅导致了W-3Bao杂合子小鼠白斑形成及纯合子小鼠贫血死亡,同时影响生殖腺发育。     

Intracellular role for sphingosine kinase 1 in intestinal adenoma cell proliferation

Sphingosine kinase (Sphk) enzymes are important in intracellular sphingolipid metabolism as well as in the biosynthesis of sphingosine 1-phosphate (S1P), an extracellular lipid mediator. Here, we show that Sphk1 is expressed and is required for small intestinal tumor cell proliferation in Apc Min/+ mice. Adenoma size but not incidence was dramatically reduced in Apc Min/+ Sphk(-/-) mice. Concomitantly, epithelial cell proliferation in the polyps was significantly attenuated, suggesting that Sphk1 regulates adenoma progression. Although the S1P receptors (S1P1R, S1P2R, and S1P3R) are expressed, polyp incidence or size was unaltered in Apc Min/+ S1p2r(-/-), Apc Min/+ S1p3r(-/-), and Apc Min/+ S1p1r(+/-) bigenic mice. These data suggest that extracellular S1P signaling via its receptors is not involved in adenoma cell proliferation. Interestingly, tissue sphingosine content was elevated in the adenomas of Apc Min/+ Sphk1(-/-) mice, whereas S1P levels were not significantly altered. Concomitantly, epithelial cell proliferation and the expression of the G1/S cell cycle regulator CDK4 and c-myc were diminished in the polyps of Apc Min/+ Sphk1(-/-) mice. In rat intestinal epithelial (RIE) cells in vitro, Sphk1 overexpression enhanced cell cycle traverse at the G1/S boundary. In addition, RIE cells treated with sphingosine but not C6-ceramide exhibited reduced cell proliferation, reduced retinoblastoma protein phosphorylation, and cyclin-dependent kinase 4 (Cdk4) expression. Our findings suggest that Sphk1 plays a critical role in intestinal tumor cell proliferation and that inhibitors of Sphk1 may be useful in the control of intestinal cancer.     

TIMP3 regulates mammary epithelial apoptosis with immune cell recruitment through differential TNF dependence

Post-lactation mammary involution is a homeostatic process requiring epithelial apoptosis and clearance. Given that the deficiency of the extracellular metalloproteinase inhibitor TIMP3 impacts epithelial apoptosis and heightens inflammatory response, we investigated whether TIMP3 regulates these distinct processes during the phases of mammary gland involution in the mouse. Here we show that TIMP3 deficiency leads to TNF dysregulation, earlier caspase activation and onset of mitochondrial apoptosis. This accelerated first phase of involution includes faster loss of initiating signals (STAT3 activation; TGFβ3) concurrent with immediate luminal deconstruction through E-cadherin fragmentation. Epithelial apoptosis is followed by accelerated adipogenesis and a greater macrophage and T-cell infiltration in Timp3(-/-) involuting glands. Crossing in Tnf deficiency abrogates caspase 3 activation, but heightens macrophage and T-cell influx into Timp3(-/-) glands. The data indicate that TIMP3 differentially impacts apoptosis and inflammatory cell influx, based on involvement of TNF, during the process of mammary involution. An understanding of the molecular factors and wound healing microenvironment of the postpartum mammary gland may have implications for understanding pregnancy-associated breast cancer risk.     

Total conversion of tissue inhibitor of metalloproteinase (TIMP) for specific metalloproteinase targeting: fine-tuning TIMP-4 for optimal inhibition of tumor necrosis factor-{alpha}-converting enzyme

Tissue inhibitors of metalloproteinases (TIMPs) are the endogenous inhibitors of the matrix metalloproteinases, the ADAMs (a disintegrin and metalloproteinase) and the ADAM-TS (ADAM with thrombospondin repeats) proteinases. There are four mammalian TIMPs (TIMP-1 to -4), and each TIMP has its own profile of metalloproteinase inhibition. TIMP-4 is the latest member of the TIMPs to be cloned, and it has never been reported to be active against the tumor necrosis factor-alpha-converting enzyme (TACE, ADAM-17). Here we examined the inhibitory properties of the full-length and the N-terminal domain form of TIMP-4 (N-TIMP-4) with TACE and showed that N-TIMP-4 is a far superior inhibitor than its full-length counterpart. Although full-length TIMP-4 displayed negligible activity against TACE, N-TIMP-4 is a slow tight-binding inhibitor with low nanomolar binding affinity. Our findings suggested that the C-terminal subdomains of the TIMPs have a significant impact over their activities with the ADAMs. To elucidate further the molecular basis that underpins TIMP/TACE interactions, we sculpted N-TIMP-4 with the surface residues of TIMP-3, the only native TIMP inhibitor of the enzyme. Transplantation of only three residues, Pro-Phe-Gly, onto the AB-loop of N-TIMP-4 resulted in a 10-fold enhancement in binding affinity; the K(i) values of the resultant mutant were almost comparable with that of TIMP-3. Further mutation at the EF-loop supported our earlier findings on the preference of TACE for leucine at this locus. Drawing together our previous experience in TACE-targeted mutagenesis by using TIMP-1 and -2 scaffolds, we have finally resolved the mystery of the selective sensitivity of TACE to TIMP-3.     

Timp3 Deficient Mice Show Resistance to Developing Breast Cancer

Timp3 is commonly silenced in breast cancer, but mechanistic studies have identified both tumor promotion and suppression effects of this gene. We have taken a genetic approach to determine the impact of Timp3 loss on two mouse models of breast cancer. Interestingly, MMTV-PyMT Timp3^−⁄− mice have delayed tumor onset and 36% of MMTV-Neu Timp3^−⁄− mice remain tumor free. TIMP3 is a regulator of TNF signaling and similar to Timp3, Tnf or Tnfr1 loss delays early tumorigenesis. The tumor suppression in Timp3 null mice requires Tnfr1, but does not result in alterations in the local immune compartment. In the mammary gland, Timps are highly expressed in the stroma and through the transplantation of tumor cells we observe that Timp3 deficiency in the host is sufficient to delay the growth of early, but not advanced tumor cells. Together our data is the first to identify a tumor promoting role of endogenous Timp3 in vivo, the spatial and temporal windows of this effect, and its dependence on Tnfr1.     

Cooperation of two ADAMTS metalloproteases in closure of the mouse palate identifies a requirement for versican proteolysis in regulating palatal mesenchyme proliferation

We have identified a role for two evolutionarily related, secreted metalloproteases of the ADAMTS family, ADAMTS20 and ADAMTS9, in palatogenesis. Adamts20 mutations cause the mouse white-spotting mutant belted (bt), whereas Adamts9 is essential for survival beyond 7.5 days gestation (E7.5). Functional overlap of Adamts9 with Adamts20 was identified using Adamts9(+/-);bt/bt mice, which have a fully penetrant cleft palate. Palate closure was delayed, although eventually completed, in both Adamts9(+/-);bt/+ and bt/bt mice, demonstrating cooperation of these genes. Adamts20 is expressed in palatal mesenchyme, whereas Adamts9 is expressed exclusively in palate microvascular endothelium. Palatal shelves isolated from Adamts9(+/-);bt/bt mice fused in culture, suggesting an intact epithelial TGFβ3 signaling pathway. Cleft palate resulted from a temporally specific delay in palatal shelf elevation and growth towards the midline. Mesenchyme of Adamts9(+/-);bt/bt palatal shelves had reduced cell proliferation, a lower cell density and decreased processing of versican (VCAN), an extracellular matrix (ECM) proteoglycan and ADAMTS9/20 substrate, from E13.5 to E14.5. Vcan haploinsufficiency led to greater penetrance of cleft palate in bt mice, with a similar defect in palatal shelf extension as Adamts9(+/-);bt/bt mice. Cell density was normal in bt/bt;Vcan(hdf)(/+) mice, consistent with reduced total intact versican in ECM, but impaired proliferation persisted in palate mesenchyme, suggesting that ADAMTS-cleaved versican is required for cell proliferation. These findings support a model in which cooperative versican proteolysis by ADAMTS9 in vascular endothelium and by ADAMTS20 in palate mesenchyme drives palatal shelf sculpting and extension.