A subject with a novel type I bare lymphocyte syndrome has tapasin deficiency due to deletion of 4 exons by Alu-mediated recombination.
HLA class I expression depends on the formation of a peptide-loading complex composed of class I heavy chain; beta(2)-microglobulin; the transporter associated with antigen processing (TAP); and tapasin, which links TAP to the heavy chain. Defects in TAP result in a class I deficiency called the type I bare lymphocyte syndrome (BLS). In the present study, we examined a subject with a novel type I BLS who does not exhibit apparent TAP abnormalities but who has a tapasin defect. The subject's TAPASIN gene has a 7.4-kilobase deletion between introns 3 and 7; an Alu repeat-mediated unequal homologous recombination may be the cause of the deletion. No tapasin polypeptide was detected in the subject's cells. The cell surface class I expression level in tapasin-deficient cells was markedly reduced but the reduction was not as profound as in TAP-deficient cells. These results suggest that tapasin deficiency is another cause of type I BLS.
Yabe
Toshio
T
Department of Research, Japanese Red Cross Central Blood Center, Tokyo, Japan. to-yabe@tokyo.bc.jrc.or.jp
Kawamura
Sumiyo
S
Sato
Masako
M
Kashiwase
Koichi
K
Tanaka
Hidenori
H
Ishikawa
Yoshihide
Y
Asao
Yoji
Y
Oyama
Junko
J
Tsuruta
Kazuma
K
Tokunaga
Katsushi
K
Tadokoro
Kenji
K
Juji
Takeo
T
D020087:Alu Elements / Q000235:genetics*; D017920:Antiporters / Q000172:deficiency* / Q000235:genetics*; D001483:Base Sequence; D005091:Exons; D005260:Female; D017353:Gene Deletion; D006650:Histocompatibility Testing; D006801:Humans; D007136:Immunoglobulins / Q000172:deficiency* / Q000235:genetics*; D007438:Introns; D026901:Membrane Transport Proteins; D008875:Middle Aged; D018832:Molecular Chaperones; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D016511:Severe Combined Immunodeficiency / Q000235:genetics*
D017920:Antiporters; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; C107762:tapasin