Hox Genes and Embryology

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Homeotic genes are master controllers that specify embryogenic structural planning and regulation of an organism. They are target genes that are essential for proper embryogensis.

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Hox genes and embryology
From the grand scheme of evolution to the individually spectacular process of embryogensis, unity and diversity have played essential roles in the formation of life on Earth. Through recent genetic and molecular studies, these concepts have been best illustrated by the surprising fact that radically disparate structures such as eyes, brain and limbs between vertebrates and invertebrates are found to have common origins (Capecchi 1997). More specifically, parallel molecular circuits are shown to initiate and guide the formation of these structures and, in general, the overall body plan of metazoas (Slack et al. 1993; McGinnis et al 1984). As a key component in many of the analogous pathways, the Homeobox (Hox) genes are found to be of great importance.
Homeotic genes are master controllers that specify embryogenic structural planning and regulation of an organism (Lufkin 1997). It was the discovery of the structural and functional similarities between Dorsophila and murine Hox genes that sparked the current revolution in our ability to appreciate the common threads which weave through the molecular fabric of development in all species (Gellon 1998). Mammalian Hox genes are not solely restricted to body demarcation. They also take part in the embryonic development of many components like the central nervous system (Boncinelli 1999), the cardiovascular system (Patterson et al. 1998), the haematopoetic system (Favier and Dolle 1997), the reproductive system (Lindsey and Wilkinson 1996) and the pulmonary system (Kappen 1996). In addition, the Hox genes have also been demonstrated to exist from sponges to plants and from insects to humans (Gehring et al. 1994). In other words, Hox genes are vital for the generation of enormous diversity that enriches our planet. Yet, despite their broad ranging properties, it is the commonality in characteristics, mechanism and regulation of Hox genes during embryogensis that fascinated so many scientists and prompted such enormous amount of research.

Collinear Characteristics of Hox genes
Sharing a highly conserved and common sequence of 180 base pairs, the Homeobox, all homeodomain molecules act as transcription factors that serve gene regulatory functions. (They brilliantly control their target genes in precise spatial and temporal manner, giving rise to two phenomenons known as Spatial Collinearity and Temporal Collinearlity respectively (Ghring et ...