For example ARL13B (ADP ribosylation factor-like GTPase 13B), a GTPase needed for proper ciliary function [81] and mutated in some cases of Joubert syndrome, can also function cell-autonomously for axonal guidance in mouse spinal cord development, outside of primary cilia, in non-canonical SHH signalling [34]. The gene discussed is ARL13B; the disease is Joubert syndrome.