Mammalian Cranial Neural Crest Cells and Facial Development. (cranial neural crest cells/facial development/mammal/retinoic acid receptor/gene expression)

Embryological Consideration of Dural AVFs in Relation to the Neural Crest and the Mesoderm

Intracranial and spinal dural arteriovenous fistulas (DAVFs) are vascular pathologies of the dural membrane with arteriovenous shunts. They are abnormal communications between arteries and veins or dural venous sinuses that sit between the two sheets of the dura mater. The dura propria faces the surface of brain, and the osteal dura faces the bone. The location of the shunt points is not distributed homogeneously on the surface of the dural membrane, but there are certain areas susceptible to DAVFs. The dura mater of the olfactory groove, falx cerebri, inferior sagittal sinus, tentorium cerebelli, and falx cerebelli, and the dura mater at the level of the spinal cord are composed only of dura propria, and these areas are derived from neural crest cells. The dura mater of the cavernous sinus, transverse sinus, sigmoid sinus, and anterior condylar confluence surrounding the hypoglossal canal are composed of both dura propria and osteal dura; this group is derived from mesoderm. Although the cause of this heterogeneity has not yet been determined, there are some specific characteristics and tendencies in terms of the embryological features. The possible reasons for the segmental susceptibility to DAVFs are summarized based on the embryology of the dura mater.

Homeobox genes and growth factors in regulation of craniofacial and tooth morphogenesis

Homeobox genes encode a special group of transcription factors that regulate gene expression in the developing embryo. The so-called Hox-cluster genes were first discovered in the Drosophila (fruit fly). They specify the identity of body segments and their patterning along the anteroposterior axis. Other homeobox-containing genes appear to regulate patterning of the head and face. The function of the Msx-1 homeobox gene has been shown to be necessary for tooth development. In general, it is thought that special combinations of homeobox genes specify the patterning of individual structures. Bone morphogenetic proteins (BMPs) are growth factors belonging to the family of transforming growth factor-beta (TGF-beta). BMPs regulate bone and cartilage development, and individual BMPs have been shown to contribute to the shaping of various skeletal elements. BMPs regulate bone and dentin formation also postnatally, and they have therapeutic potential in reparative osteogenesis and odontogenesis. BMPs also act as inductive signals between tissue layers in the embryo, and they regulate the expression of several transcription factors, including homeobox-containing genes. BMP-4 has been identified as an epithelial inductive signal in tooth development. As it is produced by early dental epithelium and regulates tooth-specific gene expression in the dental mesenchyme, including Msx-1 expression, it may be an important signal for the initiation of tooth development.

Mesoderm and jaw development in vertebrates: the role of growth factors

The head and neck arise during development as the result of a complex series of cellular and molecular interactions that begin in the fertilized egg. In this article, the role of an important class of molecules, growth factors, is examined in two main steps of the developmental sequence: the initial induction of mesoderm and the later induction of jaw cartilage and bone. The article focuses particularly on the roles of members of the transforming growth factor-beta (TGF-beta), fibroblast growth factor (FGF), and epithelial growth factor (EGF) families in these processes and current models of growth factor involvement. Possible experiments for the future are discussed.

Development of the neural crest

Mutations that affect the morphogenetic behaviour and differentiation of neural crest-derived cells in mouse embryos have been shown to alter genes that code for growth factors or growth factor receptors. Identification of these and other gene products provide opportunities to understand when and how developmentally distinct embryonic cell populations arise, and how interactions between localized developmental cues and responsive cell subpopulations can be modulated during development.