The present invention relates to compositions and methods relating to the characterization of gene function. More particularly, the present invention relates to the role of secreted protein genes involved in neurobiological disorders, and in particular, depression. In addition, the present invention provides transgenic mice comprising mutations in a secreted protein gene. Such transgenic mice are useful as models for disease and for identifying agents that modulate gene expression and gene function, and as potential treatments for various disease states and disease conditions, including depression.