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At least 19 recordsLinked to original sources
PubMed1995

Hox genes and the evolution of vertebrate axial morphology.

A common form of evolutionary variation between vertebrate taxa is the different numbers of segments that contribute to various regions of the anterior-posterior axis; cervical vertebrae, thoracic vertebrae, etc. The term 'transposition' is used to describe this phenomenon. Genetic experiments with homeotic genes in mice have demonstrated that Hox genes are in part responsible for the specification of segmental identity along the anterior-posterior axis, and it has been proposed that an axial Hox code determines the morphology of individual vertebrae (Kessel, M. and Gruss, P. (1990) Science 249, 347-379). This paper presents a comparative study of the developmental patterns of homeobox gene expression and developmental morphology between animals that have homologous regulatory genes but different morphologies. The axial expression boundaries of 23 Hox genes were examined in the paraxial mesoderm of chick, and 16 in mouse embryos by in situ hybridization and immunolocalization techniques. Hox gene anterior expression boundaries were found to be transposed in concert with morphological boundaries. This data contributes a mechanistic level to the assumed homology of these regions in vertebrates. The recognition of mechanistic homology supports the historical homology of basic patterning mechanisms between all organisms that share these genes.

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PubMedDate not supplied

Narrow axis: an inherited anomaly of the second cervical vertebra in the rabbit.

Narrow axis, an inherited anomaly resulting in a marked narrowing of the second cervical vertebra, has been observed in strain X/J rabbits. This condition is first recognizable on X rays at 32-33 days gestation. For size comparisons 21 measurements of the first five cervical vertebrae were taken on the skeletons of each of 14 strain X/J animals (7 normal and 7 with narrow axis) and 14 IIIC/J animals for control at two months of age and 27 strain X/J (11 normal and 16 narrow axis) and 14 strain IIIC/J at seven months of age. The primary effect appeared to be a premature fusion of the centrum with its neural arches. Expression is variable. The effect on the posterior articulation of the atlas appeared to be secondary and adaptive. The other cervical vertebrae and the foramen magnum were relatively unaffected. In the 20-year period encompassed in this report, X rays of 3244 rabbits were used for genetic analysis. Inheritance appears to be due to a single autosomal recessive gene with incomplete penetrance. The condition is neither sex-linked nor sex-limited. We propose the symbol nx for the gene responsible for narrow axis in the rabbit.

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