ABSTRACT
Understanding limb development not only gives insights into the outgrowth and differentiation of the limb, but also has clinical relevance. Limb development begins with two paired limb buds (forelimb and hindlimb buds), which are initially undifferentiated mesenchymal cells tipped with a thickening of the ectoderm, termed the apical ectodermal ridge (AER). As a transitional embryonic structure, the AER undergoes four stages and contributes to multiple axes of limb development through the coordination of signalling centres, feedback loops, and other cell activities by secretory signalling and the activation of gene expression. Within the scope of proximodistal patterning, it is understood that while fibroblast growth factors (FGFs) function sequentially over time as primary components of the AER signalling process, there is still no consensus on models that would explain proximodistal patterning itself. In anteroposterior patterning, the AER has a dual-direction regulation by which it promotes the sonic hedgehog (Shh) gene expression in the zone of polarizing activity (ZPA) for proliferation, and inhibits Shh expression in the anterior mesenchyme. In dorsoventral patterning, the AER activates Engrailed-1 (En1) expression, and thus represses Wnt family member 7a (Wnt7a) expression in the ventral ectoderm by the expression of Fgfs, Sp6/8, and bone morphogenetic protein (Bmp) genes. The AER also plays a vital role in shaping the individual digits, since levels of Fgf4/8 and Bmps expressed in the AER affect digit patterning by controlling apoptosis. In summary, the knowledge of crosstalk within AER among the three main axes is essential to understand limb growth and pattern formation, as the development of its areas proceeds simultaneously.
Subject(s)
Animals , Mice , Apoptosis , Body Patterning , Bone Morphogenetic Proteins/biosynthesis , Developmental Biology , Ectoderm/metabolism , Extremities/embryology , Fibroblast Growth Factor 10/metabolism , Fibroblast Growth Factors/biosynthesis , Gene Expression Regulation , Hedgehog Proteins/biosynthesis , Homeodomain Proteins/biosynthesis , Mesoderm/metabolism , Signal Transduction , Wnt Proteins/biosynthesisABSTRACT
Há aproximadamente 10 anos descobriuse um hormônio denominado FGF-23 (fator de crescimento de fibroblastos 23), um membro da família dos fatores de crescimento de fibroblastos, cujas funções atualmente conhecidas envolvem o metabolismo do fósforo (P) e a inibição da 1α hidroxilase, enzima responsável pela síntese de calcitriol. Tal descoberta possibilitou um novo entendimento sobre os mecanismos de controle do P, um elemento associado com mortalidade, especialmente na doença renal crônica (DRC). Nesta revisão descreveremos diversos aspectos deste hormônio, desde a sua descoberta, função, produção, mecanismo de ação, até os últimos estudos clínicos envolvendo o mesmo. Posteriormente, abordaremos as possíveis repercussões destes estudos na prática clínica.
Approximately 10 years ago, a member of the family of the fibroblast growth factors, the hormone FGF-23 (fibroblast growth factor 23) was discovered. Its currently known functions involve phosphorus (P) metabolism and inhibition of 1αhydroxylase, the enzyme responsible for the synthesis of calcitriol. That discovery led to a better understanding of the mechanisms of P control, an element associated with mortality, especially in chronic kidney disease. This study reviews several aspects of that hormone, such as its discovery, function, production, mechanism of action, and the most recent clinical studies about it. Afterwards, a discussion about the possible effects of those studies on clinical practice will be presented.
Subject(s)
Animals , Humans , Fibroblast Growth Factors/physiology , Chronic Disease , Fibroblast Growth Factors/biosynthesis , Fibroblast Growth Factors/blood , Kidney Diseases/blood , Kidney Diseases/metabolism , Phosphorus/metabolismABSTRACT
Os Fatores de Crescimento de Fibroblastos (®Fibroblast Growth Factors¼; FGFs) participam de fenômenos biológicos de grande importância, tais como migração, divisão e diferenciação celulares. O presente trabalho teve como objetivo central a busca de compostos biologicamente ativos através de um desenho racional de peptídeos derivados do FGF-1 e do seu receptor (FGFR-1). A partir da análise dos dados disponíveis na literatura, aliada a técnicas de modelagem molecular, foram desenhados, sintetizados e testados dois grupos de peptídeos. O primeiro conjunto (R1 - R3) é constituído por peptídeos lineares derivados do FGFR-1. Os ensaios de atividade mitogênica dos FGFs 1 e 2 em presença dos peptídeos mostram que R1 e R2 foram capazes de inibir a ação mitogênica do FGF-1...
Subject(s)
DNA/biosynthesis , Fibroblast Growth Factors/biosynthesis , Heparin , Peptides/isolation & purification , Receptors, Fibroblast Growth Factor , Signal Transduction , Mass Spectrometry , Models, Anatomic , Peptide BiosynthesisABSTRACT
Na busca por agonistas, antagonistas e inibidores de natureza peptídica do fator de crescimento de fibroblastos ácido humano (hFGF-1), iniciamos o presente trabalho fazendo uma análise conformacional teórica do peptídeo Ac-WFVGLKKNGSSKRGPRT-N`H IND. 2ï (107-123[hFGF-1]). Em trabalho anterior, este composto havia se mostrado um agonista da atividade mitogênica da proteína capaz de inibir a ligação de `ANTPOT. 125Iï-hFGF-1 aos seus receptores celulares e de se ligar à resina heparina-Sepharose (Oyama et al. 1996). Os cálculos das propriedades dinâmicas deste peptídeo (I; Tabela 1) demonstraram que ele não adotava nenhuma conformação preferencial, o que poderia justificar a baixa atividade apresentada pelo mesmo (`10 POT. 4ï vêzes menor do que a da proteína nativa)...