Biomedical subjects

M Fernandez-Teran

Publications and source records attributed to M Fernandez-Teran.

7 recordsLinked to original sources

PubMed2005

The developing limb and the control of the number of digits.

Congenital malformations of the limbs are among the most frequent congenital anomalies found in humans, and they preferentially affect the distal part--the hand or foot. The presence of extra digits, a condition called polydactyly, is the most common limb deformity of the human hand and is the consequence of disturbances in the normal program of limb development. However, despite the extensive use of the developing limb as a classical developmental model, the cellular and genetic mechanisms that control the number and identity of the digits are not completely understood. The aim of this review is to introduce the reader to the current state of knowledge in limb development and to provide the necessary background for an understanding of how deviations from the normal developmental program may lead to polydactyly.

Foot↗

PubMed2002

1 Patterning the limb before and after SHH.

The Summer Meeting of the Anatomical Society of Great Britain and Ireland was held at the University of Dundee, from 23rd to 25th July 2002. It included a symposium on 'How to make a hand'. The following are abstracts of communications and posters presented at the meeting.

Journal Article↗

PubMed2000

Pattern formation and regulation of gene expressions in chick recombinant limbs.

Recombinant limbs were performed by ensembling dissociated-reaggregated wing bud mesoderm inside an ectodermal hull. The zone of polarizing activity was excluded from the mesoderm used to perform the recombinant limbs (non-polarized recombinants), and grafted when desired (polarized recombinants). Reorganization of patterning progressively occurred in the newly formed progress zone under the influence of the apical ectodermal ridge (AER), explaining the proximo-distal gradient of morphogenesis observed in developed recombinant limbs. The AER, without the influence of the polarizing region (ZPA), was sufficient to direct outgrowth and appropriate proximo-distal patterning, as observed in the expression of the Hoxa-11 and Hoxa-13 genes. The development of the recombinant limbs coursed with symmetric AER and downregulation of Bmp expression in the mesoderm supporting a negative effect of Bmp signaling upon the apical ridge. The recombinant ectoderm maintained previously established compartments of gene expressions and organized a correct dorso-ventral patterning in the recombinant progress zone. Finally, the ZPA effect was only detected on Bmp expression and pattern formation along the antero-posterior axis.

Animals↗

PubMed2000

Role of dHAND in the anterior-posterior polarization of the limb bud: implications for the Sonic hedgehog pathway.

dHAND is a basic helix-loop-helix (bHLH) transcription factor essential for cardiovascular development. Here we analyze its pattern of expression and functional role during chick limb development. dHAND expression was observed in the lateral plate mesoderm prior to emergence of the limb buds. Coincident with limb initiation, expression of dHAND became restricted to the posterior half of the limb bud. Experimental procedures that caused mirror-image duplications of the limb resulted in mirror-image duplications of the pattern of dHAND expression along the anterior-posterior axis. Retroviral overexpression of dHAND in the limb bud produced preaxial polydactyly, corresponding to mild polarizing activity at the anterior border. At the molecular level, misexpression of dHAND caused ectopic activation of members of the Sonic hedgehog (Shh) pathway, including Gli and Patched, in the anterior limb bud. A subset of infected embryos displayed ectopic anterior activation of Shh. Other factors implicated in anterior-posterior polarization of the bud such as the most 5' Hoxd genes and Bmp2 were also ectopically activated at the anterior border. Our results indicate a role for dHAND in the establishment of anterior-posterior polarization of the limb bud.

Animals↗

PubMed1999

The recombinant limb as a model for the study of limb patterning, and its application to muscle development.

The recombinant limb is a model system that has proved fruitful for analyzing epithelial-mesenchymal interactions and understanding the functional properties of the components of the limb bud. Here we present an overview of some of the insights obtained through the use of this technique. Among these are the understanding that fore or hind limb identity is inherent to the limb bud mesoderm, that the apical ectodermal ridge (AER) is a permissive signaling center and that the limb bud ectoderm plays a central role in the control of dorsoventral polarity. Recombinant limb studies have also allowed the identification of the affected tissue component in several limb mutants. More recently this model has been applied to the study of regulation of gene expressions related to patterning. In this report we use recombinant limbs to analyze pattering of the Pax3 expressing limb muscle cell lineage in the early stages of limb development. In recombinant limbs made without the zone of polarizing activity (ZPA), myoblasts appear intermingled with other mesodermal cells at the beginning of the recombinant limb development. Rapidly thereafter, the muscle precursors segregate and organize around the central forming chondrogenic core of the recombinant. Although this segregation is reminiscent of that occurring during normal development, the myoblasts in the recombinant fail to proliferate appropriately and also fail to migrate distally. Consequently, the muscle pattern in the recombinant limb is defective indicating that normal patterning cues are absent. However, recombinant limbs polarized with a ZPA exhibited a larger mass of muscle cells and a more normal morphogenesis, supporting a role for this signaling center in limb muscle development. Finally, we have ruled out host somite contributions to recombinant limbs by grafting chick recombinant limbs to quail hosts. This initial report demonstrates the value of the recombinant limb model system for dissecting the environmental cues required for normal muscle limb patterning.

Animals↗

PubMed1997

Limb initiation and development is normal in the absence of the mesonephros.

With rapid progress in understanding the genes that control limb development and patterning interest is becoming focused on the factors that permit the emergence of the limb bud. The current hypothesis is that FGF-8 from the mesonephros induces limb initiation. To test this, the inductive interaction between the Wolffian duct and intermediate mesoderm was blocked rostral to the limb field, preventing mesonephric differentiation while maintaining the integrity of the limb field. The experimental outcome was monitored by following expression of cSim1 and Lmx1, molecular markers for the duct and the mesonephros, respectively. Evidence is presented that the intermediate mesoderm undergoes apoptosis when the inductive interaction with the Wolffian duct is blocked. fgf-8 expression was undetectable in the mesonephric area of embryos with confirmed absence of mesonephros; nevertheless, limb buds formed and limb development was normal. The mesonephros in general, and specifically its fgf-8 expression, was shown to be unnecessary for limb initiation and development; the hypothesis linking the mesonephros and limb development is not supported. Further studies of axial influences on limb initiation should now concentrate on medial structures such as Hensen's node and paraxial mesoderm; the alternative that no axial influences are required should also be examined.

Animals↗

PubMed1993

Molecular heterogeneity of chondroitin sulphate in the early developing chick wing bud.

Proteoglycans are ubiquitous extracellular matrix molecules whose role in development remains poorly understood. In the developing chick limb, the nature and possible roles of a number of extracellular matrix proteins is well documented. Much less is known of the biochemical nature, and more importantly, the roles of proteoglycans. Using a panel of monoclonal antibodies (Mabs) which recognise specific epitopes on the constituent chondroitin/dermatan sulphate chains, we show that distinct sub-populations of proteoglycans are dynamically expressed within the limb ectoderm, the ectodermal basement membrane and the limb mesenchyme. In particular, prior to chondrogenesis, chondroitin-6-sulphate-rich proteoglycans containing over-sulphated domains residue predominantly within the mesenchymal extracellular matrix ECM, whilst chondroitin-4-sulphate (C-4-S) is associated with the ectodermal basement membrane and subjacent mesenchymal ECM. At stage 24, C-4-S is also localized in the prechondrogenic condensation. Concomitantly with overt chondrogenesis, the epitopes recognized by the Mabs become restricted to the chondrifying skeletal elements and the undifferentiated distal mesenchyme. The significance of these findings has yet to be elucidated.

Animals↗