Padronização e morfogénese

Interesse da Investigação

Our group is interested in several aspects of vertebrate embryonic development. The ultimate goal of our research is to understand the molecular mechanisms that translate patterning information into morphogenetic processes during formation of the vertebrate embryo. More recently, we have also become interested in the role that those processes played in the evolution of the vertebrate body plan. In general, most of our work uses the mouse as the model system, and our approaches have a main focus on in vivo functional analyses, but we are incorporating other model systems to our approaches, mostly as a consequence of the recent Evo-Devo twist in our research. Some of the active projects in the laboratory are outlined below.

Membros do Grupo

Ana Cristina Santos	Postdoc
	Tel: 21 446 4625
Ana Casaca	Postdoc
	Tel: 21 446 4525
Ana Nóvoa	Research Technician
	Tel: 21 446 4625
Arnon Jurberg	2008 PGD PhD Student
	Tel: 21 446 4525
Ozlem Isik	2010 PIBS
	Tel: 21 446 4525

Projecto de Investigação

The role of Hox genes in the development of the vertebrate axial skeleton

The vertebrate axial skeleton is made out of repeated units called vertebrae. Vertebrae can be distributed in 5 general types, which from rostral to caudal are cervical, thoracic, lumbar, sacral and caudal. The total vertebral number and their distribution among the different groups are typical for each vertebrate species. Our work focuses on the role of Hox genes in the determination of these vertebral characteristics. In the embryo, the vertebrae derive from the somites, which are located at both sides of the neural tube all along the rostro-caudal axis of the embryo. Somite formation occurs in the embryo in close association with caudal growth from a non-segmented structure at the caudal tip of the embryo known as presomitic mesoderm. Hence, the cells lost from the rostral end of the presomitic mesoderm by their inclusion in the new-formed somites are compensated by the deposition of new cells at the caudal end of the presomitic mesoderm. Using a transgenic approach, we have shown that Hox genes provide the differentiation program to the somites when they are still being formed in the presomitic mesoderm. We are starting to understand how this process in controlled at the molecular level. In addition, we have been able to place additional pieces in the puzzle of axial patterning. We have shown that the thoracic regions results from the positive activity of Hox genes, including those in the paralog group 6, and it is not a consequence of a default state in the absence of relevant Hox activities. Thus, the global layout of the vertebrate body plan would result from coordinated and successive Hox activities. Hox group 6 will mark the beginning of the thorax, leaving the cervical region as the area between the start of Hox6 activity and the skull base. In more caudal areas of the skeleton, the activation of Hox group 10 will result in formation of the lumbar area as a consequence of its dominant block of rib inducing activities, which will later be followed by and Hox group 11 activation, which will result in formation of the sacrum. We have also recently worked out the mechanism for Hox control of rib development. Briefly, Hox proteins of the groups 6 and 10 modulate expression of Myf5 and Myf6 in the hypaxial myotome. Hox6 proteins promote this expression and Hox10 proteins repress it. Activated Myf5/Myf6 then induce expression of Fgf4 and Pdfga, which promote rib formation from the adjacent sclerotome. Importantly, the control of Myf5/Myf6 expression by Hox proteins relies on their binding to specific Myf5/Myf6 distal enhancers and requires interactions with a variety of other transcription factors. We are now exploring the mechanisms by which Hox proteins modulate Myf5/Myf6 expression. We are interested in understanding what makes Hox6 and Hox10 proteins have opposite activities when bound to the same regulatory element and how distal enhancers manage to modulate activity of these two Myf genes in a perfectly ordered spatial and temporal sequence.

Funding

PTDC/BIA-BCM/71619/2006 - Fundação para a Ciência e a Tecnologia
The molecular mechanisms by which Hox genes control development of the axial skeleton

Projecto de Investigação

The role of GNE in the pathogenesis of the Heterologous Inclusion Body Myopath

Heterologous inclusion body myopathy (HIBM) is a neuromuscular disorder, caused by mutations in UDP–N-acetylglucosamine 2-epimerase/N-acetylmannosamine (ManNAc) kinase (GNE), the key enzyme of sialic acid biosynthesis. Currently, it is assumed that the activity of the GNE gene is required in the muscle, which is the tissue affected in this disease. Accordingly, most therapeutic approaches focus on myoblast-based protocols, given this disorder presents primarily as progressive skeletal muscle wasting where muscle biopsies show rimmed vacuoles upon analysis. However, it is shown that whilst the target tissue for HIBM is the muscle, the expression and activity of GNE is much greater in the liver than in the muscle itself. We propose that GNE-dependent sialic acid produced in the liver would function in an endocrine manner to sialylate tissues throughout the body, and that the point mutations observed in HIBM may impact on the delivery of sialic acid to muscle tissue in an endocrine fashion. In order to address this hypothesis, we are creating mice carrying a GNE allele in which exon 3 is flanked by loxP sites (GNEflox), so that it becomes prone to inactivation upon expression of the Cre recombinase. We will then remove GNE specifically from the liver or muscle by crossing these mice with transgenic lines that express the Cre recombinase in hepatocytes (Albumin-Cre or MX-Cre inducible) or in muscle (MEF2C-Cre or MCK-rtTA/TetOCre inducible). Phenotypic analyses of these mice over a range of developmental ages and with GNE inactivation from early development or induced at different stages during adulthood will allow a clear evaluation of the relative importance of the hepatic and muscular GNE activity in the physiopathology of HIBM. In addition, they will provide critical information to direct future therapeutic approaches whilst providing useful models for the evaluation of these therapeutic avenues for HIBM in the future.

Funding

ARM Grant#024 – Advancement of Research for Myopathies
Tissue specific evaluation of GNE driven sialic acid production in vivo using cre/lox transgenesis

Publicações

(selected) Updated May (2010).

Mallo, M., Wellik, D. M. & Deschamps, J. (2010). Hox Genes and Regional Patterning of the Vertebrate Body Plan Dev. Biol (in press)

Vinagre, T., Moncaut, N., Carapuço, M., Nóvoa, A., Bom, J. & Mallo, M. (2010). Evidence for a myotomal Hox/Myf cascade governing non-autonomous control of rib specification within global vertebral domains Dev. Cell 18 :655–661

Young, T., Rowland, J. E., van de Ven, C.,Bialecka, M., Novoa, A., Carapuco, M., van Nes, J., de Graaff, W., Duluc, I., Freund, J. N., Beck, F., Mallo, M. & Deschamps, J. (2009). Hox and Cdx genes differentially regulate posterior axial growth in mammalian embryos Dev Cell 17 :516-526

Schiedlmeier, B.*, Santos, A. C., Ribeiro, A., Moncaut, N. Lesinski, D. Auer, H., Kornacker, K., Ostertag, W., Baum, C., Mallo, M.* & Klump, H. (* joint corresponding authors). (2007). HOXB4’s roadmap to stem cell expansion. Proc. Natl. Acad. Sci. USA 104 :16952-16957

Correia, A. C., Costa, M., Moraes, F., Bom, J. Nóvoa, A. & Mallo, M. (2007). Bmp2 is required for migration but not for induction of neural crest cells in the mouse. Dev. Dyn. 236 :2493-2501

Mallo, M. & Magli, M. C. (2006). A look at life from the homeodomain. EMBO reports 7 :976-980

Carapuço, M., Nóvoa, A. Bobola, N. & Mallo, M. (2005). Hox genes specify vertebral types in the presomitic mesoderm Genes Dev 19 :2116-2121

Moraes, F., Nóvoa, A., Jerome-Majewska, L. A., Papaioannou, V. E. & Mallo, M. (2005). Tbx1 is required for proper neural crest migration and to stabilize spatial patterns during middle and inner ear development. Mech. Dev 122 :199-212

Bobola, N., Carapuço, M., Ohnemus, S., Kanzler, B., Leibbrandt, A., Neubüser, A, Drouin, J. & Mallo, M. (2003). Mesenchymal patterning by Hoxa2 requires blocking FGF-dependent activation of Ptx1. Development 130 :3403-3414