ARHGEF7 and Miyoshi myopathy: Given that the known MM genes include DCC and NTN1, which are critical for Netrin-1/DCC axon guidance, and a third MM gene, RAD51, may function downstream of Netrin-1 (16), we hypothesized that ARHGEF7 is also involved in Netrin-1/DCC signaling and is important for axon guidance to the midline.