Cloning and Characterization of a Novelrho-Type GTPase-Activating Protein Gene (ARHGAP6) from the Critical Region for Microphthalmia with Linear Skin Defects

Abstract

Microphthalmia with linear skin defects syndrome (MLS) is an X-linked dominant, male-lethal disorder associated with chromosomal rearrangements that result in deletions of the distal short arm of the X chromosome. In an effort to isolate expressed sequences from the 500-kb MLS critical region in Xp22.3, exons were trapped from 14 overlapping cosmids. Using exon connection followed by cDNA library screening, we identified a 2.4-kb contig of cDNA clones spanning 170 kb of genomic sequence in the MLS deletion region. Northern analysis of this cDNA detected a prominent ∼4.2-kb transcript and a less abundant ∼6-kb transcript in all tissues examined, with additional transcripts in skeletal muscle. Sequence analysis revealed a coding region of 601 amino acids contained in 12 exons, with a splice variant isoform of 495 amino acids. The predicted protein sequence of the gene, namedARHGAP6,contains homology to the GTPase-activating (GAP) domain of therhoGAP family of proteins, which has been implicated in the regulation of actin polymerization at the plasma membrane in several cellular processes. The possible role of theARHGAP6protein in the pathogenesis of MLS is discussed.