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. For a number of years, we have explored different developmental processes, including the ear formation, the neural crest induction/migration and differentiation of branchial arches. Specific emphasis was put on the role genes like Hoxa2, Ptx1, Bmp2 or Tbx1 played in those processes. Most recently our focus moved a bit and we are now exploring other biological processes, but still mostly linked to vertebrate embryonic development. They are outlined below.

Membros do Grupo

Jennifer Rowland	Postdoc
	Tel: 21 446 4666
Joana Almeida	Research Technician
	Tel: 21 446 4625
Ana Nóvoa	Research Technician
	Tel: 21 446 4625
Teresa Gomes	Trainee
	Tel: 21 446 4687
Isabel Guerreiro	Trainee
	Tel: 21 446 4525
Sofia Pereira	Trainee
	Tel: 21 440 7900
Filipa Moraes	2005 PDIGC PhD Student
	Tel: 21 446 4525
Tânia Vinagre	2006 PDIGC PhD Student
	Tel: 21 446 4525
Arnon Jurberg	2008 PGD PhD Student
	Tel: 21 446 4514

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 add one further piece in the puzzle of axial patterning. While it has already been shown in the last few years that formation of global areas of the axial skeleton is controlled by a restricted set of Hox genes (e.g., Hox group 10 control formation of the lumbar area and Hox group 11 control formation of the sacrum), it was not clear if the thoracic area was a default state in the absence of Hox gene expression or if it required the positive activity of specific Hox genes. We have found that the paralog group 6 has this activity. Recent experiments in our laboratory have shown that transgenic embryos expressing Hoxb6 in the presomitic mesoderm have ribs associated to all their vertebrae. We are now searching for the genes that mediate the activities of the Hox group 10 in removing ribs and Hox group 6 in producing them, taking advantage of the antagonist activities of these two genes.

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

Remodelation of the aortic tree

The heart outflow tract from newborn and adult animals (i.e. the arteries that organize the distribution of the blood to the body as it leaves the heart chambers) is formed in the embryo by a complex morphogenetic process that involves the formation and remodelation of the embryonic aortic arches. During this process, the first and second aortic arches disappear between days 9 and 11 of embryonic age. We are investigating how this process is controlled at the cellular and molecular levels. We have found that the first two aortic arches fail to become associated with smooth muscle cells, which in this area of the embryo are derived from the neural crest. We hypothesized that the presence or absence of these neural crest-derived smooth muscle cells plays a role in the remodelation of the aortic arches. We are testing this hypothesis by creating transgenic mice, which over express, in the first two arches, genes able to induce differentiation into smooth muscle cells (like myocardin). Some of our preliminary data using double immunofluorescence and 3D reconstruction of the optical sections obtained with the confocal microscope indicate that the presence of smooth muscle cells might indeed prevent aortic arch vessels from degenerate. We are further analyzing this issue and performing experiments to determine the molecular basis for this process.

Funding

Bolsa de Investigação Pfizer Professor João Cid dos Santos, 2004- Pfizer
Real time in vivo studies of heart outflow tract morphogenesis and the role of the Tbx1 gene

Projecto de Investigação

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

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 November (2008).

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