Grey, a novel mutation in the murine Lyst gene, causes the beige phenotype by skipping of exon 25.
The murine beige mutant phenotype and the human Chediak-Higashi syndrome are caused by mutations in the murine Lyst (lysosomal trafficking regulator) gene and the human CHS gene, respectively. In this report we have analyzed a novel murine mutant Lyst allele, called Lyst(bg-grey), that had been found in an ENU mutation screen and named grey because of the grey coat color of affected mice. The phenotype caused by the Lyst(bg-grey) mutation was inherited in a recessive fashion. Melanosomes of melanocytes associated with hair follicles and the choroid layer of the eye, as well as melanosomes in the neural tube-derived pigment epithelium of the retina, were larger and irregularly shaped in homozygous mutants compared with those of wild-type controls. Secretory vesicles in dermal mast cells of the mutant skin were enlarged as well. Test crosses with beige homozygous mutant mice (Lyst(bg)) showed that double heterozygotes (Lyst(bg)/Lyst(bg-grey)) were phenotypically indistinguishable from either homozygous parent, demonstrating that the ENU mutation was an allele of the murine Lyst gene. RT-PCR analyses revealed the skipping of exon 25 in Lyst(bg-grey) mutants, which is predicted to cause a missense D2399E mutation and the loss of the following 77 amino acids encoded by exon 25 but leave the C-terminal end of the protein intact. Analysis of the genomic Lyst locus around exon 25 showed that the splice donor at the end of exon 25 showed a T-to-C transition point mutation. Western blot analysis suggests that the Lyst(bg-grey) mutation causes instability of the LYST protein. Because the phenotype of Lyst(bg) and Lyst(bg-grey) mutants is indistinguishable, at least with respect to melanosomes and secretory granules in mast cells, the Lyst(bg-grey) mutation defines a critical region for the stability of the murine LYST protein.
Runkel
Fabian
F
Anatomisches Institut, Universität Bonn, Germany. f.runkel@uni-bonn.de
Büssow
Heinrich
H
Seburn
Kevin L
KL
Cox
Gregory A
GA
Ward
Diane McVey
DM
Kaplan
Jerry
J
Franz
Thomas
T
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D005091:Exons / Q000235:genetics*; D005260:Female; D006200:Hair Color / Q000235:genetics*; D006579:Heterozygote; D006720:Homozygote; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008407:Mast Cells / Q000378:metabolism; D008544:Melanocytes / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D010375:Pedigree; D010641:Phenotype; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000378:metabolism; D011506:Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D022142:Secretory Vesicles / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D033921:Vesicular Transport Proteins
D047908:Intracellular Signaling Peptides and Proteins; C491133:Lyst protein, mouse; D011506:Proteins; D033921:Vesicular Transport Proteins