Many of these genes are homeobox genes...
Human Growth in Sickness and in Health
Homeobox genes in vertebrate development
E.Boncinelli
A number of gene families have been identified in the past 20 years which play a role in the control of the development of the body, and in particular of the central nervous system, of vertebrates. Many of these genes are homeobox genes. Homeobox genes are regulatory genes characterised by the presence of a specific, evolutionarily conserved, DNA sequence termed homeobox, able to code for a protein domain of some 60 amino acid residues, termed homeodomain. It is through the action of their homeodomain that the protein products of the homeobox genes, the homeoproteins, bind to the regulatory regions of specific genes and control their expression. The first homeobox genes were identified in the fruit fly, Drosophila melanogaster through the study of the genetic control of its body plan. Here a complex of eight homeobox genes, termed homeotic genes, control the identity of the various body regions along the anterior-posterior axis. In vertebrates 39 genes have been identified which are the true homologues of the Drosophila homeotic genes. They have been termed Hox genes and are located in four homologous chromosomal loci. They appear to play a role in the specification of body regions along the rostro-caudal body axis and provide positional cues for the developing neural tube and in particular for the rhombencephalon (the developing hindbrain) and spinal cord, from the branchial area to the tail, but are not involved in controlling the development of the head and of brain regions anterior to the hindbrain. Conversely, other homeobox genes belonging to other families have been reported to play such a role. Among them, the four genes belonging to the Otx and Emx families occupy a particular position and show an extremely restricted expression domain. In particular, Otx2 appears to play a crucial role in the early establishment of the rostral brain; Otx1 and Otx2 cooperate to define the posterior boundary of midbrain; and Emx1 and Emx2 play a major role in the developing cerebral cortex, whose extension is determined by the Emx2 gene products. These results may be relevant for the deeper understanding of congenital defects and multifactorial disorders.
Homeobox genes in vertebrate development
E.Boncinelli
A number of gene families have been identified in the past 20 years which play a role in the control of the development of the body, and in particular of the central nervous system, of vertebrates. Many of these genes are homeobox genes. Homeobox genes are regulatory genes characterised by the presence of a specific, evolutionarily conserved, DNA sequence termed homeobox, able to code for a protein domain of some 60 amino acid residues, termed homeodomain. It is through the action of their homeodomain that the protein products of the homeobox genes, the homeoproteins, bind to the regulatory regions of specific genes and control their expression. The first homeobox genes were identified in the fruit fly, Drosophila melanogaster through the study of the genetic control of its body plan. Here a complex of eight homeobox genes, termed homeotic genes, control the identity of the various body regions along the anterior-posterior axis. In vertebrates 39 genes have been identified which are the true homologues of the Drosophila homeotic genes. They have been termed Hox genes and are located in four homologous chromosomal loci. They appear to play a role in the specification of body regions along the rostro-caudal body axis and provide positional cues for the developing neural tube and in particular for the rhombencephalon (the developing hindbrain) and spinal cord, from the branchial area to the tail, but are not involved in controlling the development of the head and of brain regions anterior to the hindbrain. Conversely, other homeobox genes belonging to other families have been reported to play such a role. Among them, the four genes belonging to the Otx and Emx families occupy a particular position and show an extremely restricted expression domain. In particular, Otx2 appears to play a crucial role in the early establishment of the rostral brain; Otx1 and Otx2 cooperate to define the posterior boundary of midbrain; and Emx1 and Emx2 play a major role in the developing cerebral cortex, whose extension is determined by the Emx2 gene products. These results may be relevant for the deeper understanding of congenital defects and multifactorial disorders.
posted by redazione at 10:18 AM
0 Comments:
Posta un commento
<< Home