Biology subjects

Hubmacher, D.

Publications and source records attributed to Hubmacher, D..

5 recordsLinked to original sources

bioRxiv2026

Dysregulated TGFb-ERK Signaling Drives Aberrant Extracellular Matrix Production in Noonan Syndrome-Associated Pulmonary Valve Stenosis

Pulmonary valve stenosis (PVS) is the most common congenital heart defect in Noonan syndrome (NS) and related RASopathies, yet the molecular mechanisms linking pathogenic variants to the valve pathology remain poorly defined. Here, we utilized a human iPSC-based valve differentiation platform to generate the cardiac valve cell lineages--including fibrosa and spongiosa valve interstitial cell (VIC) subtypes. CRISPR-edited iPSCs harboring NS gain-of-function RAS/MAPK and Noonan syndrome with multiple lentigines (NSML) dominant-negative RAS/MAPK variants exhibited early defects in mesodermal and endocardial specification in all genotypes. Additionally, NS-iPSC endocardial cells exhibited defects in endothelial-to-mesenchymal transition (EndMT) specifically towards fibrosa VICs, which was most pronounced in PTPN11N308D (N308D) cells. Single-cell transcriptomics revealed widespread dysregulation of extracellular matrix (ECM) programs in N308D fibrosa VICs, including increased expression of collagens and proteoglycans, as well as dysregulation of multiple genes involved in ECM remodeling. We also detected activation of RAS-MAPK, TGF{beta}, and fibrosis-associated pathways in our transcriptional dataset. Mass spectrometry-based phosphoproteomics confirmed coordinated increases in ERK, PKC, and stress-related kinases, as well as enhanced activity of the TGF{beta} receptor. Functionally, N308D fibrosa VICs exhibited exaggerated upregulation of ECM genes in the presence of TGF{beta}2 ligand, suggesting that these cells are hypersensitive to TGF{beta} stimulation. Furthermore, we demonstrated that this pathological ECM-program occurs independently of BAMBI, a negative regulator of TGF{beta} signaling that was found to be decreased in N308D fibrosa VICs. Lastly, we performed histopathological analyses of stenotic pulmonary valves from two NS infants, which demonstrated marked overproduction and disorganization of ECM, mirroring the findings from our iPSC-based disease model. Together, our data reveal a central mechanism where NS-associated alleles sensitize fibrosa VICs to TGF{beta}, which leads to aberrant downstream signaling and drives the pathological ECM program in NS-associated PVS.

cell biology↗

bioRxiv2025

Combined ADAMTS10 and ADAMTS17 inactivation exacerbates bone shortening and skin phenotypes

Weill-Marchesani syndrome (WMS) is characterized by severe short stature, short hands and feet (brachydactyly), joint contractures, tight skin, and heart valve, eye, and skin anomalies. Whereas recessive WMS is caused by mutations in ADAMTS10, ADAMTS17, or LTBP2, dominant WMS is caused by mutations in FBN1 (encoding fibrillin-1). Since bone growth is driven by chondrocyte proliferation and hypertrophy in the growth plates, the genetics of WMS suggests that the affected ECM proteins act within the same pathway to regulate chondrocyte and growth plate function. Here, we investigated the role of the secreted ADAMTS proteases ADAMTS10 and ADAMTS17 in growth plate function and ECM formation. We generated Adamts10;Adamts17 double knockout (DKO) mice, which showed significant postnatal lethality compared to single Adamts10 or Adamts17 KO mice. Importantly, we observed severe bone shortening DKO mice, which correlated with a narrower hypertrophic zone in their growth plates. ADAMTS17 substrates identified by N-terminomics and yeast two-hybrid screening identified the ECM proteins fibronectin and collagen VI (COL6). However, validation experiments did not reveal direct proteolysis of either fibronectin or COL6 by ADAMTS17. We then investigated ECM formation in primary ADAMTS10- and ADAMTS17-deficient skin fibroblasts and observed compromised fibronectin deposition concomitant with aberrant intracellular accumulation of fibrillin-1. These findings support a role for ADAMTS17 in ECM protein secretion and assembly. Collectively, our data suggest that ADAMTS10 and ADAMTS17 regulate bone growth by regulating chondrocyte hypertrophy or hypertrophic chondrocyte turnover. Mechanistically, ADAMTS17 appears to be a critical regulator of ECM protein secretion or pericellular matrix assembly, whereas ADAMTS10 likely modulates ECM formation at later stages, possibly regulating the spatio-temporal deposition of fibrillin isoforms.

cell biology↗

bioRxiv2022

Secreted ADAMTS-like 2 promotes myoblast differentiation by potentiating Wnt signaling

The formation of multinucleated contractile myofibers from muscle stem cells during myogenesis is indispensable for skeletal muscle formation. Myogenesis is governed by myogenic regulatory transcription factors, including MYOD. However, very few MYOD- regulated effector proteins were shown to be sufficient to promote myogenesis. Here, we identified an unexpected role for the secreted matricellular protein ADAMTS-like 2 (ADAMTSL2) as a rheostat for Wnt signaling during myogenesis downstream of MYOD. ADAMTSL2 expression was induced during myoblast differentiation and ADAMTSL2 was required for myoblast differentiation. ADAMTSL2 ablation in myogenic precursor cells resulted in aberrant muscle architecture in vivo. The pro-myogenic ADAMTSL2 function was dependent on WNT ligands. Mechanistically, ADAMTSL2 potentiated WNT signaling by binding to WNT ligands and WNT receptors. Finally, we identified a WNT-binding ADAMTSL2 peptide that was sufficient to promote myogenesis. Since ADAMTSL2 was previously described as a negative regulator of TGF{beta} signaling in fibroblasts, ADAMTSL2 now emerges as a signaling node that could integrate and fine-tune WNT, TGF{beta} and potentially other signaling pathways within the dynamic microenvironment of differentiating myoblasts during skeletal muscle development and regeneration.

cell biology↗

bioRxiv2022

Promoting translational readthrough to augment fibrillin-1 (FBN1) deposition in Marfan syndrome fibroblasts: A proof-of-concept study.

Marfan syndrome (MFS) is a connective tissue disorder characterized by long bone overgrowth, enlargement of the aorta, ocular anomalies and other symptoms. Current treatment focuses on managing aortic aneurysms to avoid dissection or rupture. However, no cures are available. MFS is caused by one of >1,800 dominant pathogenic variants in FBN1, which encodes the extracellular matrix (ECM) protein fibrillin-1. A significant number of FBN1 variants result in premature termination codons (PTCs). Recently, small molecules were identified that can promote translational readthrough of PTCs and were evaluated in preclinical and clinical trials for several genetic disorders. Here, we show that the translational readthrough drugs ataluren and gentamicin ameliorated FBN1 deposition in some MFS patient-derived skin fibroblast lines harboring PTC variants in FBN1. In contrast, inhibitors of NMD were cytotoxic to the skin fibroblast lines that we analyzed. We conclude that promoting translational readthrough of PTC variants in FBN1 could result in a therapeutic benefit for MFS patients with specific PTCs in FBN1 and that its efficacy will likely depend on the PTC sequence context, the amino acids that are incorporated in FBN1 after PTC suppression and the overall increase of FBN1 deposition in the ECM.

cell biology↗

bioRxiv2018

Limb- and tendon-specific Adamtsl2 deletion identifies a soft tissue mechanism modulating bone length

Disproportionate distal limb shortening is the hallmark of acromelic dysplasias. Among them, geleophysic dysplasia is a rare, frequently lethal condition characterized by severe short stature, musculoskeletal, cardiac, pulmonary, and skin anomalies. Geleophysic dysplasia results from dominant fibrillin-1 (FBN1) or recessive ADAMTSL2 mutations, suggesting a functional link between ADAMTSL2 and FBN1. Mice lacking ADAMTSL2 die at birth, precluding analysis of postnatal skeletal growth and mechanisms underlying the skeletal anomalies of geleophysic dysplasia. We show that Adamtsl2 is expressed in limb soft tissues, predominantly in tendon. Expression in developing bones is limited to their terminal cell layers that are destined to become articular cartilage and is absent in growth plate cartilage. Adamtsl2 conditional deletion in limb mesenchyme using Prxl-Cre led to an acromelic dysplasia, providing a suitable model for investigation of geleophysic dysplasia. Unexpectedly, conditional Adamtsl2 deletion using Scx-Cre, a tendon-specific deleter, also impaired skeletal growth. Specific morphogenetic anomalies were seen in Achilles tendon, along with FBN1 accumulation. Thus, ADAMTSL2, shown here to bind fibrillin microfibrils in vitro, limits fibrillin microfibril formation in tendons and promotes tendon growth. The findings suggest that reduced bone growth in geleophysic dysplasia results from external tethering by short tendons rather than intrinsic growth plate anomalies.

developmental biology↗