The neurobeachin gene spans the common fragile site FRA13A.

Common fragile sites are normal constituents of chromosomal structure prone to chromosomal breakage. In humans, the cytogenetic locations of more than 80 common fragile sites are known. The DNA at 11 of them has been defined and characterized at the molecular level. According to the Genome Database, the common fragile site FRA13A maps to chromosome band 13q13.2. Here, we identify the precise genomic position of FRA13A, and characterize the genetic complexity of the fragile DNA sequence. We show that FRA13A breaks are limited to a 650 kb region within the neurobeachin (NBEA) gene, which genomically spans approximately 730 kb. NBEA encodes a neuron-specific multidomain protein implicated in membrane trafficking that is predominantly expressed in the brain and during development.