Abstract:
The doublecortin-like (DCX) domains serve as protein-interaction platforms. DCX
tandem domains appear in the product of the X-linked doublecortin (DCX) gene, in
retinitis pigmentosa –1 (RP1), as well as in other gene products. Mutations in the human
DCX gene are associated with abnormal neuronal migration, epilepsy, and mental
retardation; mutations in RP1 are associated with a form of inherited blindness, while
DCDC2 has been associated with dyslectic reading disabilities. Motivated by the possible
importance of this gene family, a thorough analysis to detect all family members in the
mouse was conducted. The DCX-repeat gene superfamily is composed of eleven
paralogs, and we cloned the DCX domains from nine different genes. Our study
questioned which functions attributed to the DCX domain, are conserved among the
different members. Our results suggest that the proteins with the DCX-domain have
conserved and unique roles in microtubule regulation and signal transduction. All the
tested proteins stimulated microtubule assembly in vitro. Proteins with tandem repeats
stabilized the microtubule cytoskeleton in transfected cells, while those with single
repeats localized to actin-rich subcellular structures, or the nucleus. All tested proteins interacted with components of the JNK/MAP-kinase pathway, while only a subset
interacted with Neurabin 2, and a non-overlapping group demonstrated actin association.
The sub-specialization of some members due to confined intracellular localization, and
protein interactions may explain the success of this superfamily.