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Mol Genet Metab. 2008 Jun;94(2):248-54. doi: 10.1016/j.ymgme.2008.02.009. Epub 2008 Apr 7.

A novel missense mutation (G43S) in the switch I region of Rab27A causing Griscelli syndrome.

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  • 1Section on Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, Bethesda, MD 20892, USA. wwestbro@mail.nih.gov

Abstract

The autosomal recessive Griscelli syndrome type II (GSII) is caused by mutations in the RAB27A gene. Typical clinical features include immunological impairment, silver-gray scalp hair, eyelashes and eyebrows and hypomelanosis of the skin. Rabs help determine the specificity of membrane trafficking steps within cells. In melanocytes, the GTP-bound form of Rab27A associates with the membranes of mature fully-pigmented melanosomes through its geranylgeranyl group. Once attached, Rab27A recruits the downstream effector Melanophilin (Mlph) and the actin-dependent motor protein Myosin Va (MyoVa). The molecular Rab27A/Mlph/MyoVA tripartite complex, which links melanosomes to the peripheral actin network, is required to achieve melanosome transfer to surrounding keratinocytes in the epidermis. Here we report a novel homozygous missense mutation c.127G>A, p.G43S in exon 2 of the RAB27A gene of an Afghani GSII patient. Laser scanning confocal microscopy showed that the G43S mutation, which is located in the highly conserved switch I region of Rab27A, induces perinuclear localization of melanosomes in normal melanocytes, and fails to restore melanosomes to the actin-rich periphery in GSII melanocytes. Co-immunoprecipitation studies showed that Rab27A(G43S) fails to interact with its effector Melanophilin, indicating that the switch I region functions in the recruitment of Rab effector proteins.

PMID:
18397837
[PubMed - indexed for MEDLINE]
PMCID:
PMC2430933
Free PMC Article
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