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Sebastian FANTINI

Ricercatore t.d. art. 24 c. 3 lett. A
Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze sede ex-Sc. Biomediche

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Pubblicazioni

2023 - Inhibition of ERK1/2 signaling prevents bone marrow fibrosis by reducing osteopontin plasma levels in a myelofibrosis mouse model [Articolo su rivista]
Bianchi, Elisa; Rontauroli, Sebastiano; Tavernari, Lara; Mirabile, Margherita; Pedrazzi, Francesca; Genovese, Elena; Sartini, Stefano; Dall'Ora, Massimiliano; Grisendi, Giulia; Fabbiani, Luca; Maccaferri, Monica; Carretta, Chiara; Parenti, Sandra; Fantini, Sebastian; Bartalucci, Niccolò; Calabresi, Laura; Balliu, Manjola; Guglielmelli, Paola; Potenza, Leonardo; Tagliafico, Enrico; Losi, Lorena; Dominici, Massimo; Luppi, Mario; Vannucchi, Alessandro Maria; Manfredini, Rossella
abstract

Clonal myeloproliferation and development of bone marrow (BM) fibrosis are the major pathogenetic events in myelofibrosis (MF). The identification of novel antifibrotic strategies is of utmost importance since the effectiveness of current therapies in reverting BM fibrosis is debated. We previously demonstrated that osteopontin (OPN) has a profibrotic role in MF by promoting mesenchymal stromal cells proliferation and collagen production. Moreover, increased plasma OPN correlated with higher BM fibrosis grade and inferior overall survival in MF patients. To understand whether OPN is a druggable target in MF, we assessed putative inhibitors of OPN expression in vitro and identified ERK1/2 as a major regulator of OPN production. Increased OPN plasma levels were associated with BM fibrosis development in the Romiplostim-induced MF mouse model. Moreover, ERK1/2 inhibition led to a remarkable reduction of OPN production and BM fibrosis in Romiplostim-treated mice. Strikingly, the antifibrotic effect of ERK1/2 inhibition can be mainly ascribed to the reduced OPN production since it could be recapitulated through the administration of anti-OPN neutralizing antibody. Our results demonstrate that OPN is a novel druggable target in MF and pave the way to antifibrotic therapies based on the inhibition of ERK1/2-driven OPN production or the neutralization of OPN activity.

2021 - Gene expression profile correlates with molecular and clinical features in patients with myelofibrosis [Articolo su rivista]
Rontauroli, S.; Castellano, S.; Guglielmelli, P.; Zini, R.; Bianchi, E.; Genovese, E.; Carretta, C.; Parenti, S.; Fantini, S.; Mallia, S.; Tavernari, L.; Sartini, S.; Mirabile, M.; Mannarelli, C.; Gesullo, F.; Pacilli, A.; Pietra, D.; Rumi, E.; Salmoiraghi, S.; Mora, B.; Villani, L.; Grilli, A.; Rosti, V.; Barosi, G.; Passamonti, F.; Rambaldi, A.; Malcovati, L.; Cazzola, M.; Bicciato, S.; Tagliafico, E.; Vannucchi, A. M.; Manfredini, R.
abstract

Myelofibrosis (MF) belongs to the family of classic Philadelphia-negative myeloproliferative neoplasms (MPNs). It can be primary myelofibrosis (PMF) or secondary myelofibrosis (SMF) evolving from polycythemia vera (PV) or essential thrombocythemia (ET). Despite the differences, PMF and SMF patients are currently managed in the same way, and prediction of survival is based on the same clinical and genetic features. In the last few years, interest has grown concerning the ability of gene expression profiles (GEPs) to provide valuable prognostic information. Here, we studied the GEPs of granulocytes from 114 patients with MF, using a microarray platform to identify correlations with patient characteristics and outcomes. Cox regression analysis led to the identification of 201 survival-related transcripts characterizing patients who are at high risk for death. High-risk patients identified by this gene signature displayed an inferior overall survival and leukemia-free survival, together with clinical and molecular detrimental features included in contemporary prognostic models, such as the presence of high molecular risk mutations. The high-risk group was enriched in post-PV and post-ET MF and JAK2V617F homozygous patients, whereas pre-PMF was more frequent in the low-risk group. These results demonstrate that GEPs in MF patients correlate with their molecular and clinical features, particularly their survival, and represent the proof of concept that GEPs might provide complementary prognostic information to be applied in clinical decision making.

2021 - Mutated clones driving leukemic transformation are already detectable at the single-cell level in CD34-positive cells in the chronic phase of primary myelofibrosis [Articolo su rivista]
Parenti, Sandra; Rontauroli, Sebastiano; Carretta, Chiara; Mallia, Selene; Genovese, Elena; Chiereghin, Chiara; Peano, Clelia; Tavernari, Lara; Bianchi, Elisa; Fantini, Sebastian; Sartini, Stefano; Romano, Oriana; Bicciato, Silvio; Tagliafico, Enrico; Della Porta, Matteo; Manfredini, Rossella
abstract

Disease progression of myeloproliferative neoplasms is the result of increased genomic complexity. Since the ability to predict disease evolution is crucial for clinical decisions, we studied single-cell genomics and transcriptomics of CD34-positive cells from a primary myelofibrosis (PMF) patient who progressed to acute myeloid leukemia (AML) while receiving Ruxolitinib. Single-cell genomics allowed the reconstruction of clonal hierarchy and demonstrated that TET2 was the first mutated gene while FLT3 was the last one. Disease evolution was accompanied by increased clonal heterogeneity and mutational rate, but clones carrying TP53 and FLT3 mutations were already present in the chronic phase. Single-cell transcriptomics unraveled repression of interferon signaling suggesting an immunosuppressive effect exerted by Ruxolitinib. Moreover, AML transformation was associated with a differentiative block and immune escape. These results suggest that single-cell analysis can unmask tumor heterogeneity and provide meaningful insights about PMF progression that might guide personalized therapy.

2021 - Promoter Methylation Leads to Decreased ZFP36 Expression and Deregulated NLRP3 Inflammasome Activation in Psoriatic Fibroblasts [Articolo su rivista]
Bertesi, M.; Fantini, S.; Alecci, C.; Lotti, R.; Martello, A.; Parenti, S.; Carretta, C.; Marconi, A.; Grande, A.; Pincelli, C.; Zanocco Marani, T.
abstract

The mRNA-destabilizing protein tristetraprolin (TTP), encoded by the ZFP36 gene, is known to be able to end inflammatory responses by directly targeting and destabilizing mRNAs encoding pro-inflammatory cytokines. We analyzed its role in psoriasis, a disease characterized by chronic inflammation. We observed that TTP is downregulated in fibroblasts deriving from psoriasis patients compared to those deriving from healthy individuals and that psoriatic fibroblasts exhibit abnormal inflammasome activity compared to their physiological counterpart. This phenomenon depends on TTP downregulation. In fact, following restoration, TTP is capable of directly targeting for degradation NLRP3 mRNA, thereby drastically decreasing inflammasome activation. Moreover, we provide evidence that ZFP36 undergoes methylation in psoriasis, by virtue of the presence of long stretches of CpG dinucleotides both in the promoter and the coding region. Besides confirming that a perturbation of TTP expression might underlie the pathogenesis of psoriasis, we suggest that deregulated inflammasome activity might play a role in the disease alongside deregulated cytokine expression.

2020 - Depletion of Trichoplein (TpMs) Causes Chromosome Mis-Segregation, DNA Damage and Chromosome Instability in Cancer Cells [Articolo su rivista]
Lauriola, Angela; Martello, Andrea; Fantini, Sebastian; Marverti, Gaetano; Zanocco-Marani, Tommaso; Davalli, Pierpaola; Guardavaccaro, Daniele; Mai, Sabine; Caporali, Andrea; D’Arca, Domenico
abstract

Mitotic perturbations frequently lead to chromosome mis-segregation that generates genome instability, thereby triggering tumor onset and/or progression. Error-free mitosis depends on fidelity-monitoring systems that ensure the temporal and spatial coordination of chromosome segregation. Recent investigations are focused on mitotic DNA damage response (DDR) and chromosome mis-segregations with the aim of developing more efficient anti-cancer therapies. We previously demonstrated that trichoplein keratin filament binding protein (TpMs) exhibits hallmarks of a tumor suppressor gene in cancer-derived cells and human tumors. Here, we show that silencing of TpMs expression results in chromosome mis-segregation, DNA damage and chromosomal instability. TpMs interacts with Mad2, and TpMs depletion results in decreased levels of Mad2 and Cyclin B1 proteins. All the genetic alterations observed are consistent with both defective activation of the spindle assembly checkpoint and mitotic progression. Thus, low levels of TpMs found in certain human tumors may contribute to cellular transformation by promoting genomic instability.

2020 - Genomic analysis of hematopoietic stem cell at the single-cell level: Optimization of cell fixation and whole genome amplification (WGA) protocol [Articolo su rivista]
Carretta, C.; Mallia, S.; Genovese, E.; Parenti, S.; Rontauroli, S.; Bianchi, E.; Fantini, S.; Sartini, S.; Tavernari, L.; Tagliafico, E.; Manfredini, R.
abstract

Single-cell genomics has become the method of choice for the study of heterogeneous cell populations and represents an elective application in defining the architecture and clonal evolution in hematological neoplasms. Reconstructing the clonal evolution of a neoplastic population therefore represents the main way to understand more deeply the pathogenesis of the neoplasm, but it is also a potential tool to understand the evolution of the tumor population with respect to its response to therapy. Pre-analytical phase for single-cell genomics analysis is crucial to obtain a cell population suitable for single-cell sorting, and whole genome amplification is required to obtain the necessary amount of DNA from a single cell in order to proceed with sequencing. Here, we evaluated the impact of different methods of cellular immunostaining, fixation and whole genome amplification on the efficiency and yield of single-cell sequencing.

2020 - Wnt/CTNNB1 signal transduction pathway inhibits the expression of ZFP36 in squamous cell carcinoma, by inducing transcriptional repressors SNAI1, SLUG and TWIST [Articolo su rivista]
Zanfi, E. D.; Fantini, S.; Lotti, R.; Bertesi, M.; Marconi, A.; Grande, A.; Manfredini, R.; Pincelli, C.; Zanocco-Marani, T.
abstract

The Wnt/CTNNB1 pathway is often deregulated in epithelial tumors. The ZFP36 gene, encoding the mRNA binding protein Tristetraprolin (TTP), is downregulated in several cancers, where it has been described to behave as a tumor suppressor. By this report, we show that Wnt/CTNNB1 pathway is constitutively activated, and ZFP36 expression is downregulated in Squamous Cell Carcinoma (SCC) cell lines compared to normal keratinocytes. Moreover, we suggest that the decrease of ZFP36 expression might depend on the activity of transcriptional repressors SNAI1, SLUG and TWIST, whose expression is induced by Wnt/CTNNB1, highlighting a potential regulatory mechanism underlying ZFP36 downregulation in epithelial cancers.

2019 - Physiological expression of miR-130a during differentiation of CD34+ human hematopoietic stem cells results in the inhibition of monocyte differentiation [Articolo su rivista]
Mammoli, F.; Parenti, S.; Lomiento, M.; Gemelli, C.; Atene, C. G.; Grande, A.; Corradini, R.; Manicardi, Agnese; Fantini, S.; Zanocco-Marani, T.; Ferrari, S.
abstract

MicroRNAs (miRNA) are small noncoding RNAs that regulate gene expression by targeting mRNAs in a sequence specific manner, thereby determining their degradation or inhibiting translation. They are involved in processes such as proliferation, differentiation and apoptosis by fine-tuning the expression of genes underlying such events. The expression of specific miRNAs is involved in hematopoietic differentiation and their deregulation contributes to the development of hematopoietic malignancies such as acute myeloid leukemia (AML). miR-130a is over-expressed in AML. Here we show that miR-130a is physiologically expressed in myeloblasts and down-regulated during monocyte differentiation. Gain- and loss-of-function experiments performed on CD34+ human hematopoietic stem cells confirmed that expression of miR-130a inhibits monocyte differentiation by interfering with the expression of key transcription factors HOXA10, IRF8, KLF4, MAFB and PU-1. The data obtained in this study highlight that the correct modulation of miR-130a is necessary for normal differentiation to occur and confirming that deregulation of this miRNA might underlie the differentiation block occurring in AML.

2018 - HOX cluster-embedded micro-RNAs and cancer [Articolo su rivista]
Fantini, S.; Salsi, V.; Zappavigna, V.
abstract

HOX cluster-embedded micro-RNAs and cancer.

2018 - KLF4 mediates the effect of 5-ASA on the b-catenin pathway in colon cancer cells [Articolo su rivista]
Parenti, Sandra; Montorsi, Lucia; Fantini, Sebastian; Mammoli, Fabiana; Gemelli, Claudia; Atene, Claudio Giacinto; Losi, Lorena; Frassineti, Chiara; Calabretta, Bruno; Tagliafico, Enrico; Ferrari, Sergio; Zanocco-Marani, Tommaso; Grande, Alexis
abstract

Mesalazine (5-ASA) is an aminosalicylate anti-inflammatory drug capable of inducing m-protocadherin, a protein expressed by colorectal epithelial cells that is downregulated upon malignant transformation. Treatment with 5-ASA restores m-protocadherin expression and promotes the sequestration of b-catenin to the plasma membrane. Here, we show that 5-ASA–induced m-protocadherin expression is directly regulated by the KLF4 transcription factor. In addition, we suggest the existence of a dual mechanism whereby 5-ASA–mediated b-catenin inhibition is caused by m-protocadherin–dependent sequestration of b-catenin to the plasma membrane and by the direct binding of KLF4 to b-catenin. In addition, we found that 5-ASA treatment suppresses the expression of miR-130a and miR-135b, which target KLF4 mRNA, raising the possibility that this mechanism is involved in the increased expression of KLF4 induced by 5-ASA.

2017 - The miR-196b miRNA inhibits the GATA6 intestinal transcription factor and is upregulated in colon cancer patients [Articolo su rivista]
Fantini, Sebastian; Salsi, Valentina; Reggiani, Luca; Maiorana, Antonino; Zappavigna, Vincenzo
abstract

Objective: To explore the possible misexpression of the microRNA miR-196b in colorectal cancer (CRC) and its role in controlling the expression of GATA6, a putative target gene crucial to intestinal cell homeostasis and tumorigenesis. Design: The expression of miR-196b was analysed by qRT-PCR in surgical resection samples from a cohort of sporadic colon cancer patients. Manipulations of miR-196b expression were performed to demonstrate its inhibition of GATA6 protein levels. Results: We found that miR-196b is significantly upregulated in pre-treatment surgical resection samples from a cohort of sporadic colon cancer patients. The upregulation of miR-196b correlates with less severe clinicopathological characteristics, such as early tumor stage and absence of lymph node metastases. We show that in CRC cells, miR-196b targets the mRNA of GATA6, a transcription factor involved in the homeostasis and differentiation of intestinal epithelial cells, and a positive regulator of the Wnt/β-catenin pathway. We moreover found that the increase of miR-196b correlates with a reduced GATA6 protein expression in colon cancer patients. Conclusion: Our results establish miR-196b as a post-transcriptional inhibitor of GATA6 in CRC cells, implicating miR-196b function in gene regulatory pathways crucial to intestinal cell homeostasis and tumorigenesis. Our results furthermore suggest a role of miR-196b expression in CRC, as an antagonist of GATA6 function in tumor cells, thus providing the basis for a potential targeting strategy for the treatment of CRC.

2016 - NUP98 fusion oncoproteins interact with the APC/CCdc20 as a pseudosubstrate and prevent mitotic checkpoint complex binding [Articolo su rivista]
Salsi, Valentina; Fantini, Sebastian; Zappavigna, Vincenzo
abstract

NUP98 is a recurrent partner gene in translocations causing acute myeloid leukemias and myelodisplastic syndrome. The expression of NUP98 fusion oncoproteins has been shown to induce mitotic spindle defects and chromosome missegregation, which correlate with the capability of NUP98 fusions to cause mitotic checkpoint attenuation. We show that NUP98 oncoproteins physically interact with the APC/CCdc20 in the absence of the NUP98 partner protein RAE1, and prevent the binding of the mitotic checkpoint complex to the APC/CCdc20. NUP98 oncoproteins require the GLEBS-like domain present in their NUP98 moiety to bind the APC/CCdc20. We found that NUP98 wild-type is a substrate of APC/CCdc20 prior to mitotic entry, and that its binding to APC/CCdc20 is controlled via phosphorylation of a PEST sequence located within its C-terminal portion. We identify S606, within the PEST sequence, as a key target site, whose phosphorylation modulates the capability of NUP98 to interact with APC/CCdc20. We finally provide evidence for an involvement of the peptidyl-prolyl isomerase PIN1 in modulating the possible conformational changes within NUP98 that lead to its dissociation from the APC/CCdc20 during mitosis. Our results provide novel insight into the mechanisms underlying the aberrant capability of NUP98 oncoproteins to interact with APC/CCdc20 and to interfere with its function.

2015 - MicroRNA-196b is transcribed from an autonomous promoter and is directly regulated by Cdx2 and by posterior Hox proteins during embryogenesis [Articolo su rivista]
Fantini, Sebastian; Salsi, Valentina; Vitobello, Antonio; Rijli, Filippo M.; Zappavigna, Vincenzo
abstract

The miR-196 miRNA gene family located within the Hox gene clusters has been shown to function during embryogenesis and to be aberrantly expressed in various malignancies, including leukaemia, melanoma, and colorectal cancer. Despite its involvement in numerous biological processes, the control of miR-196 expression is still poorly defined. We identified the miR-196b promoter and found that the mature miR-196b originates from a large, non-coding primary transcript, which starts within an autonomous TATA box promoter and is not in physical continuity with either the Hoxa10 or Hoxa9 main primary transcripts. A ~680bp genomic fragment, spanning the pri-miR-196b transcription start site, is sufficient to recapitulate the neural tube expression pattern of miR-196 during embryogenesis. This region contains potential binding sites for Cdx and 5'Hox transcription factors. Two of these sites revealed to be necessary for neural tube expression and were bound in vivo by Cdx2 and Hoxd13. We show that Cdx2 is required for miR-196 expression and that both Cdx2 and 5'Hox, but not 3'Hox, are able to activate the miR-196b promoter. The possible role of Cdx2- and 5'Hox-mediated regulation of miR-196 expression in vertebrate anterior-posterior (AP) axis formation during embryogenesis is discussed.

2014 - NUP98 fusion oncoproteins promote aneuploidy by attenuating the mitotic spindle checkpoint [Articolo su rivista]
Salsi, V.; Ferrari, S.; Gorello, P.; Fantini, S.; Chiavolelli, F.; Mecucci, C.; Zappavigna, V.
abstract

NUP98 is a recurrent fusion partner in chromosome translocations that cause acute myelogenous leukemia. NUP98, a nucleoporin, and its interaction partner Rae1, have been implicated in the control of chromosome segregation, but their mechanistic contributions to tumorigenesis have been unclear. Here, we show that expression of NUP98 fusion oncoproteins causes mitotic spindle defects and chromosome missegregation, correlating with the capability of NUP98 fusions to cause premature securin degradation and slippage from an unsatisfied spindle assembly checkpoint (SAC). NUP98 fusions, unlike wild-type NUP98, were found to physically interact with the anaphase promoting complex/cyclosome (APC/C)(Cdc20) and to displace the BubR1 SAC component, suggesting a possible mechanistic basis for their interference with SAC function. In addition, NUP98 oncoproteins displayed a prolonged half-life in cells. We found that NUP98 stability is controlled by a PEST sequence, absent in NUP98 oncoproteins, whose deletion reproduced the aberrant SAC-interfering activity of NUP98 oncoproteins. Together, our findings suggest that NUP98 oncoproteins predispose myeloid cells to oncogenic transformation or malignant progression by promoting whole chromosome instability.

2012 - An N-terminal G11A mutation in HOXD13 causes synpolydactyly and interferes with Gli3R function during limb pre-patterning. [Articolo su rivista]
Brison, N; Debeer, P; Fantini, Sebastian; Oley, C; Zappavigna, Vincenzo; Luyten, Fp; Tylzanowski, P.
abstract

Synpolydactyly (SPD) is a distal limb anomaly characterized by incomplete digit separation and the presence of supernumerary digits in the syndactylous web. This phenotype has been associated with mutations in the homeodomain or polyalanine tract of the HOXD13 gene. We identified a novel mutation (G11A) in HOXD13 that is located outside the previously known domains and affects the intracellular half life of the protein. Misexpression of HOXD13(G11A) in the developing chick limb phenocopied the human SPD phenotype. Finally, we demonstrated through in vitro studies that this mutation has a destabilizing effect on GLI3R uncovering an unappreciated mechanism by which HOXD13 determines the patterning of the limb.

2011 - Control of pelvic girdle development by genes of the Pbx family and Emx2. [Articolo su rivista]
Capellini, Td; Handschuh, K; Quintana, L; Ferretti, E; Di Giacomo, G; Fantini, Sebastian; Vaccari, G; Clarke, Sl; Wenger, Am; Bejerano, G; Sharpe, J; Zappavigna, Vincenzo; Selleri, L.
abstract

Genes expressed in the somatopleuric mesoderm, the embryonic domain giving rise to the vertebrate pelvis, appear important for pelvic girdle formation. Among such genes, Pbx family members and Emx2 were found to genetically interact in hindlimb and pectoral girdle formation. Here, we generated compound mutant embryos carrying combinations of mutated alleles for Pbx1, Pbx2, and Pbx3, as well as Pbx1 and Emx2, to examine potential genetic interactions during pelvic development. Indeed, Pbx genes share overlapping functions and Pbx1 and Emx2 genetically interact in pelvic formation. We show that, in compound Pbx1;Pbx2 and Pbx1;Emx2 mutants, pelvic mesenchymal condensation is markedly perturbed, indicative of an upstream control by these homeoproteins. We establish that expression of Tbx15, Prrx1, and Pax1, among other genes involved in the specification and development of select pelvic structures, is altered in our compound mutants. Lastly, we identify potential Pbx1-Emx2-regulated enhancers for Tbx15, Prrx1, and Pax1, using bioinformatics analyses.

2010 - Scapula development is governed by genetic interactions of Pbx1 with its family members and with Emx2 via their cooperative control of Alx1 [Articolo su rivista]
T. D., Capellini; G., Vaccari; E., Ferretti; Fantini, Sebastian; M., He; Pellegrini, Massimo; L., Quintana; G., Di Giacomo; J., Sharpe; L., Selleri; Zappavigna, Vincenzo
abstract

The genetic pathways underlying shoulder blade development are largely unknown, as gene networks controlling limb morphogenesis have limited influence on scapula formation. Analysis of mouse mutants for Pbx and Emx2 genes has suggested their potential roles in girdle development. In this study, by generating compound mutant mice, we examined the genetic control of scapula development by Pbx genes and their functional relationship with Emx2. Analyses of Pbx and Pbx1;Emx2 compound mutants revealed that Pbx genes share overlapping functions in shoulder development and that Pbx1 genetically interacts with Emx2 in this process. Here, we provide a biochemical basis for Pbx1;Emx2 genetic interaction by showing that Pbx1 and Emx2 can bind specific DNA sequences as heterodimers. Moreover, the expression of genes crucial for scapula development is altered in these mutants, indicating that Pbx genes act upstream of essential pathways for scapula formation. In particular, expression of Alx1, an effector of scapula blade patterning, is absent in all compound mutants. We demonstrate that Pbx1 and Emx2 bind in vivo to a conserved sequence upstream of Alx1 and cooperatively activate its transcription via this potential regulatory element. Our results establish an essential role for Pbx1 in genetic interactions with its family members and with Emx2 and delineate novel regulatory networks in shoulder girdle development.

2009 - A G220V substitution within the N-terminal transcription regulating domain of HOXD13 causes a variant synpolydactyly phenotype. [Articolo su rivista]
Fantini, Sebastian; Vaccari, Giulia; Brison, N; Debeer, P; Tylzanowski, P; Zappavigna, Vincenzo
abstract

The 5' members of the HoxD gene cluster (paralogous groups 9-13) are crucial for correct vertebrate limb patterning. Mutations in the HOXD13 gene have been found to cause synpolydactyly (SPD) and other limb malformations in human. We report the identification in a Greek family of a variant form of SPD caused by a novel missense mutation that substitutes glycine for valine in position 220 (G220V) of HOXD13. This mutation represents the first substitution of an amino acid located outside of the HOXD13 homeodomain that causes autopodal limb malformations. We have characterized this mutation at the molecular level and found that the G220V substitution causes a significant impairment of the capacity of HOXD13 to bind DNA and regulate transcription. HOXD13(G220V) was found to be deficient in both activating and repressing transcription through HOXD13-responsive regulatory elements. In accordance with these results, a comparison of the activities of HOXD13 and HOXD13(G220V) in vivo, using retrovirus-mediated misexpression in developing chick limbs, showed that the G220V mutation impairs the capacity of HOXD13 to perturb the development of proximal limb skeletal elements and to ectopically activate the transcription of the Hand2 target gene. We moreover show that the G220V mutation compromises the stability of the HOXD13 protein within cells and causes its partial accumulation in the cytosol in the form of subtle aggregates. Taken together, our results establish that the G220V substitution does not produce a dominant-negative effect or a gain-of-function, but represents a dominant loss-of-function mutation revealing haploinsufficiency of HOXD13 in human.