[Molecular basis for establishment and maintenance of dendritic trees]

The human brain receives, processes, stores and transmits complex information with great fidelity. The neuronal network that underlies these functions is comprised of an estimated 10(11) neurons linked by 10(14) synaptic connections between two structurally and functionally different neurites, axons and dendrites. Precise patterning of dendrites as well as axons is essential for correct wiring and function of neural circuits. Given that dendrites are a fundamental determinant of neural wiring, it is not surprising that dendrite defects are associated with a variety of human diseases such as Down's syndrome, Rett syndrome, and Fragile-X syndrome. In this review, I summarize our current understanding of cellular and molecular mechanisms that regulate dendritic field formation and influence the shaping of dendritic arbors. In particular, I attempt to address (1) how neurons take the polarity, (2) how the individual dendritic branches are developed, (3) how the size, shape, and complexity of dendritic arbors are regulated, and (4) following establishment of dendritic fields, how arbors are maintained and in some case how arbors change over time.