Cellular retinoic acid binding protein: cloning and expression of the gene

The work described in this thesis aims at the elucidation of mechanisms that govern cellular differentiation. To gain insight in these processes, molecular changes associated with differentiation of embryonal carcinoma cells were investigated. As similar differentiation events are assumed to occur during normal embryogenesis, this may contribute to the understanding of early embryonic development. Chapter II describes the isolation and preliminary characterization of a number of CDNA clones corresponding to gene sequences that are induced upon differentiation of a mouse embryonal carcinoma cell line. After determination of the nucleotide sequences, we were able to establish the identity of four of the selected eDNA clones. One of these was found to encode the cellular retinoic acid binding protein CRABP. In view of the known involvement of RA in cellular differentiation and embryonic pattern formation, we decided to focus our attention on analysis of the CRAB!' gene. The chapters III and W deal with the expression of CRABP during embryoni7d'~velopment. Our data show that the CRABP gene exhibits a spatia-temporally speCified expression pattern in both mouse and chick embryos. A striking correlation is observed between CRABP expression and susceptibility to RA-induced malformations. In chapter V, tissue culture experiments will be described that provide a better understanding of the role of CRABP in RA-mediated signal transduction. Finally, we have started to study the regulation of CRABP gene expression. These experiments, which include a detailed analysis of the CRABP promoter region, will be presented in chapter VI. The results presented in this thesis show that a gene that is induced upon differentiation of an EC cell line is also differentially expressed during embryogenesis. Our in vivo expression data point to an important role for CRABP in the regulation of RA mediated morphogenetic events