A mouse forward-genetic screen for novel loci critical for neural development

Correct wiring of the nervous system is a complex and daunting task. Within the human nervous system, billions of neurons must initiate axonal projections that traverse through a network of other neurons, other cells, and other tissue types to connect with their appropriate synaptic partners. Along their trajectories, axons must be able to survey the external surroundings and appropriately read directional cues provided by the environment. Using modern molecular genetics and embryonic stem cell technologies, mutations have been engineered into many loci in the mouse genome to produce an array of mice with interesting aberrations in neural connectivity. The vast number of events as well as the complexity and diversity of circuits underscores the total of as yet unidentified molecular cues. While fruitful and informative, knockout mouse technologies are slow and, by definition, hypothesis driven, making these reverse-genetic approaches incommensurate with genome-wide screens to identify novel molecules critical for neural development. With the completion of the mouse genome sequence, the characterization of strain-specific mouse polymorphisms, the discovery of potent chemical mutagens, and the genetic isolation of various mouse strains, it is now possible to induce high-density point mutations, screen for phenotypes, and map the underlying causes of the identified developmental anomalies. Thus, we have undertaken a forward-genetic, or phenotype-based, screen to identify novel loci involved in neural connectivity. Here we report the design and efficacy of a high-throughput screen for peripheral nervous system development. In addition, we describe five lines identified through the use of this technique and the mapping of the genetic mutations underlying these phenotypes