Positional cloning of the Chediak-Higashi syndrome gene: genetic mapping of the beige locus on mouse chromosome 13.

BACKGROUND: Chediak-Higashi syndrome (CHS) is a systemic disorder of human and mouse (beige, bg) that is characterized by aberrant intracellular protein kinesis and lysosomal trafficking. Affected individuals exhibit a severe primary immune deficiency that principally affects the function of granulocytes and cytolytic lymphocytes and partial oculocutaneous albinism, platelet dysfunction, and neurodegeneration. Chediak-Higashi syndrome is inherited as an autosomal recessive Mendelian trait in human and mouse and maps on proximal mouse Chromosome 13.
METHODS: To clone positionally the defective gene in CHS, we have generated a large number of backcross mice who segregate for beige. Genomic DNA from these mice was genotyped for 26 genetic markers known to map on proximal mouse Chromosome 13.
RESULTS: By segregation analysis, bg was localized to a 0.24 centiMorgan interval and was shown to cosegregate with 6 genetic markers (Nid, Estm9, D13Mit56, D13Mit162, D13Mit237, and D13Mit240). Two of these loci, Nid and Estm9, are genes and represent candidates for bg. Nidogen (Nid) encodes an extracellular matrix protein that is a component of basement membranes. Estm9 is a sequence that is transcribed ubiquitously in mouse embryos and encodes a protein of unknown function. Mutation analysis of Nid and Estm9 was undertaken in 6 bg alleles; no differences were observed between bg and coisogenic controls by analysis of Northern blots, Southern blots, or by quantitative reverse transcription and polymerase chain reaction.
CONCLUSIONS: These studies indicate that a genomic rearrangement affecting Nid or Estm9 does not underlie bg. The bg locus has been localized on mouse Chromosome 13 with sufficient precision to enable rapid cloning of the bg non-recombinant interval and eventual identification of the gene for Chediak-Higashi syndrome among sequences within the interval.