Networks of neurons, joined together by synaptic connections, represent basic

functional units of the brain. Neuronal cells are very heterogeneous. Even a small unit of

the nervous system such as the retina contains more than 50 physiologically and

morphologically distinct neuron types where each type is tied with stereotyped

connectivity into the neuronal network and is dedicated to specific aspects of information

processing. Moreover, within a morphologically recognizable class of neurons subspecializations

exist that can be appreciated through analysis of the molecular repertoire

of the cells. Understanding the developmental and molecular mechanisms contributing to

the unique morphological and functional properties, as well as the specific synaptic

connectivity of neurons represents one of the key questions in current neurobiological

research.One hypothesis is that neuronal cell populations carry molecular recognition

tags that contribute to targeted growth, selective wiring, and specific synaptic properties.

Such tags would have to be highly polymorphic with different isoforms mediating cellular

recognition events through binding partners. At the same time, such recognition tags

should couple such extracellular interactions to a common cellular response. The recent

development of new technologies for genome-wide proteomic and transcriptional

analysis in combination with transgenic technologies provide a unique opportunity for

unraveling molecular codes of neuronal identity. The goal of this project is to further

develop such approaches and to apply them to the dissection and interpretation of

neuronal identity in the mammalian central nervous system. In particular in this project I

will focus on one highly polymorphic class of neuronal cell surface receptors called

neurexins (NRXN) which show a remarkable molecular diversity with over 3,000 variants

generated through alternative splicing and which are prime candidates to encode some

aspect of neuronal identity