Quox 1 homeobox protein is expressed in postmitotic sensory neurons of dorsal root ganglia

Human synemin gene generates splice variants encoding two distinct intermediate filament proteins

Intermediate filament (IF) proteins are constituents of the cytoskeleton, conferring resistance to mechanical stress, and are encoded by a dispersed multigene family. In man we have identified two isoforms (180 and 150 kDa) of the IF protein synemin. Synemin alpha and beta have a very short N-terminal domain of 10 amino acids and a long C-terminal domain consisting of 1243 amino acids for the alpha isoform and 931 amino acids for the beta isoform. An intronic sequence of the synemin beta isoform is used as a coding sequence for synemin alpha. Both mRNA isoforms (6.5 and 7.5 kb) result from alternative splicing of the same gene, which has been assigned to human chromosome 15q26.3. Analyses by Northern and Western blot revealed that isoform beta is the predominant isoform in striated muscles, whereas both isoforms (alpha and beta) are present in almost equal quantities in smooth muscles. Co-transfection and immunolabeling experiments indicate that both synemin isoforms are incorporated with desmin to form heteropolymeric IFs. Furthermore synemin and desmin are found aggregated together in certain pathological situations.

qBrn-2, a POU III gene in quail: distinct developmental expression revealed by a specific antibody

We examined qBrn-2 protein expression in quail from its onset to final profile with a specific antibody we prepared. qBrn-2 expression employed onset-widespread-restriction pattern, and precisely concurred with formation and differentiation of neural tube. qBrn-2 protein was also located outside neural tube. Obvious differences in expression were observed compared with that of Brn-2.

Factors controlling lineage specification in the neural crest

The neural crest is a transitory tissue of the vertebrate embryo that originates in the neural folds, populates the embryo, and gives rise to many different cell types and tissues of the adult organism. When neural crest cells initiate their migration, a large fraction of them are still pluripotent, that is, capable of generating progeny that consists of two or more distinct phenotypes. To elucidate the cellular and molecular mechanisms by which neural crest cells become committed to a particular lineage is therefore crucial to the understanding of neural crest development and represents a major challenge in current neural crest research. This chapter discusses selected aspects of neural crest cell differentiation into components of the peripheral nervous system. Topics include sympathetic neurons, the adrenal medulla, primary sensory neurons of the spinal ganglia, some of their mechanoreceptive and proprioceptive end organs, and the enteric nervous system.

On the homology of structures and Hox genes: the vertebral column

Research on expression patterns of Hox genes has revealed a surprisingly high conservation among vertebrates. In agreement with this conservation, a correlation has been found between the anterior limits of expression areas of certain Hox genes and the borders between morphological regions of the vertebral axis. These similarities are striking and important, but also counterintuitive, unless there are strong selection pressures to protect this conservatism. It is important to identify the selective forces that maintain these conservative networks. These selective forces can be due to pleiotropy or to internal selection. Discussed are the selective factors that are involved in the evolutionary constraint on the number of cervical vertebral numbers in mammals. Factors involved are due to internal selection and involve susceptibility to cancer, stillbirths and neuronal problems. It is intriguing how similar genetic networks can lead to fundamentally different animals. Clearly the same genes are used for different purposes. It is therefore important to try to find these differences. The search, for homology between organisms, and the enthusiasm about similarities that come with it, at times impedes the discovery of such differences. I have searched the literature for differences within vertebrates in the functioning and expression patterns of Hox genes during the development of the vertebral axis. The ensuing implications for homology of structures and genes are discussed. The vertebral column is a promising model system for the evaluation of the relationship between homologous Hox genes and homologous structures because of the large conservation of Hox gene expression patterns along the anterior axis. However, extensive remodelling of the vertebrate column indicates that important changes in the genetic basis must have taken place. A survey of the literature indicates that the correlation between Hox gene expression areas and vertebral regions is not such that one can predict the borders between vertebral regions on the basis of Hox gene expression patterns. The involvement of Hox genes in the development of identity of vertebrae is complex and the problems regarding the value of gene expression patterns for the determination of anatomical homology are discussed.