Genetic analysis of patients with leukocyte adhesion deficiency: genomic sequencing reveals otherwise undetectable mutations.
OBJECTIVE
The aim of this study was to analyze mutations in DNA from patients with leukocyte adhesion deficiency (LAD), an immunodeficiency caused by absence of the beta(2) subunit (CD18) of the leukocyte integrins LFA-1 (CD11a/CD18), Mac-1 (CD11b/CD18), p150,95 (CD11c/CD18), and CR4 (CD11d/CD18).


METHODS
We developed genomic DNA PCR sequencing to detect mutations not only in exons but also in introns.


RESULTS
Eight LAD patients were analyzed, of which five had homozygous mutations, i.e., a 0.8-kb deletion, a branchpoint mutation in intron 5 causing mRNA missplicing, a nonsense mutation, and two missense mutations. Four of these mutations are novel. We cotransfected the two mutant CD18 proteins with normal CD11a, b, or c in COS cells. This resulted in absence of all three beta(2) integrins on the surface of cells transfected with CD18(252Arg). However, CD18(593Cys) supported some LFA-1 and p150,95 formation in COS cells. The other three patients were compound heterozygotes in which only one allele had previously been characterized, because the other alleles were undetectable at the cDNA level. We identified the unknown mutations as a novel two-nucleotide deletion, a nonsense mutation, and a single nucleotide deletion.


CONCLUSIONS
Our method allows identification of mutations in CD18 from genomic DNA. This opens the possibility of early prenatal diagnosis of LAD and reliable carrier detection.
Roos
Dirk
D
Central Laboratory Netherlands Blood Transfusion Service (CLB) and Laboratory for Experimental and Clinical Immunology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. d_roos@clb.nl
Meischl
Christof
C
de Boer
Martin
M
Simsek
Suat
S
Weening
Ron S
RS
Sanal
Ozden
O
Tezcan
Ilhan
I
Güngör
Tayfun
T
Law
S K Alex
SK
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018845:CD11 Antigens / Q000235:genetics; D018821:CD18 Antigens / Q000235:genetics*; D019556:COS Cells; D018389:Codon, Nonsense; D003241:Consanguinity; D004252:DNA Mutational Analysis; D005260:Female; D017353:Gene Deletion; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007438:Introns; D018370:Leukocyte-Adhesion Deficiency Syndrome / Q000235:genetics*; D008297:Male; D009154:Mutation; D020125:Mutation, Missense; D016133:Polymerase Chain Reaction; D012326:RNA Splicing / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D014162:Transfection
D018845:CD11 Antigens; D018821:CD18 Antigens; D018389:Codon, Nonsense; D012333:RNA, Messenger