Arl2l1 (Arl2-like protein 1) and Arl13 form a subfamily of the Arf family of small GTPases. Arl2l1 was identified in human cells during a search for the gene(s) responsible for Bardet-Biedl syndrome (BBS). Like Arl6, the identified BBS gene, Arl2l1 is proposed to have cilia-specific functions. Arl13 is found on the X chromosome, but its expression has not been confirmed; it may be a pseudogene.