Identification and characterization of a novel XK splice site mutation in a patient with McLeod syndrome.
BACKGROUND
McLeod syndrome is a rare X-linked neuroacanthocytosis syndrome with hematologic, muscular, and neurologic manifestations. McLeod syndrome is caused by mutations in the XK gene whose product is expressed at the red blood cell (RBC) surface but whose function is currently unknown. A variety of XK mutations has been reported but no clear phenotype-genotype correlation has been found, especially for the point mutations affecting splicing sites.


METHODS
A man suspected of neuroacanthocytosis was evaluated by neurologic examination, electromyography, muscle biopsy, muscle computed tomography, and cerebral magnetic resonance imaging. The McLeod RBC phenotype was disclosed by blood smear and immunohematology analyses and then confirmed at the biochemical level by Western blot analysis. The responsible XK mutation was characterized at the mRNA level by reverse transcription-polymerase chain reaction (PCR), identified by genomic DNA sequencing, and verified by allele-specific PCR.


RESULTS
A novel XK splice site mutation (IVS1-1G>A) has been identified in a McLeod patient who has developed hematologic, neuromuscular, and neurologic symptoms. This is the first reported example of a XK point mutation affecting the 3' acceptor splice site of Intron 1, and it was demonstrated that this mutation indeed induces aberrant splicing of XK RNA and lack of XK protein at the RBC membrane.


CONCLUSIONS
The detailed characterization at the molecular biology level of this novel XK splice site mutation associated with the clinical description of the patient contributes to a better understanding of the phenotype-genotype correlation in the McLeod syndrome.
Arnaud
Lionel
L
National Institute of Blood Transfusion, Paris, France. larnaud@ints.fr
Salachas
François
F
Lucien
Nicole
N
Maisonobe
Thierry
T
Le Pennec
Pierre-Yves
PY
Babinet
Jérôme
J
Cartron
Jean-Pierre
JP
D000328:Adult; D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004912:Erythrocytes; D006402:Hematologic Diseases / Q000150:complications* / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008297:Male; D054546:Neuroacanthocytosis / Q000150:complications* / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D022821:RNA Splice Sites / Q000235:genetics*
D026921:Amino Acid Transport Systems, Neutral; D022821:RNA Splice Sites; C087883:XK protein, human