Neuralin-1 is a novel Chordin-related molecule expressed in the mouse neural plate

Cysteine-rich repeats (CRs) of the type described in Chordin constitute conserved domains present in an expanding family of secreted molecules. These motifs were shown to mediate directly the antagonism of BMP signaling by Chordin and play a major role during development. Here we report the cloning and expression pattern of neuralin-1, a new member of the chordin family. The mouse cDNA was cloned by homology with a human genomic sequence encoding putative CRs. In the human genome, neuralin-1 transcripts are encoded by 8 exons that span a region of at least 80 kilobases located on chromosome Xq22.1-23. Neuralin-1 is a 333 amino acid protein containing three CRs, two of them highly similar to the Chordin CRs that bind BMP. Like chordin, neuralin-1 is able to induce secondary axes after mRNA injection in Xenopus embryos. Interestingly, during late gastrulation, neuralin-1 and chordin present distinct and complementary expression patterns in the mouse: neuralin-1 expression starts in the neural plate at mid-gastrulation, whereas chordin expression at that stage is restricted to the node and midline mesendoderm. Later on, neuralin-1 expression becomes restricted to discrete regions of the central nervous system and to derivatives of the neural crest cells. During organogenesis, neuralin-1 presents a broad expression pattern in many tissues such as dorsal root ganglia, gut, condensing cartilages of the skeleton and developing hair follicles.