Differential expression of wild-type and mutant NMMHC-IIA polypeptides in blood cells suggests cell-specific regulation mechanisms in MYH9 disorders.
MYH9 disorders such as May-Hegglin anomaly are characterized by macrothrombocytopenia and cytoplasmic granulocyte inclusion bodies that result from mutations in MYH9, the gene for nonmuscle myosin heavy chain-IIA (NMMHC-IIA). We examined the expression of mutant NMMHC-IIA polypeptide in peripheral blood cells from patients with MYH9 5770delG and 5818delG mutations. A specific antibody to mutant NMMHC-IIA (NT629) was raised against the abnormal carboxyl-terminal residues generated by 5818delG. NT629 reacted to recombinant 5818delG NMMHC-IIA but not to wild-type NMMHC-IIA, and did not recognize any cellular components of normal peripheral blood cells. Immunofluorescence and immunoblotting revealed that mutant NMMHC-IIA was present and sequestrated only in inclusion bodies within neutrophils, diffusely distributed throughout lymphocyte cytoplasm, sparsely localized on a diffuse cytoplasmic background in monocytes, and uniformly distributed at diminished levels only in large platelets. Mutant NMMHC-IIA did not translocate to lamellipodia in surface activated platelets. Wild-type NMMHC-IIA was homogeneously distributed among megakaryocytes derived from the peripheral blood CD34(+) cells of patients, but coarse mutant NMMHC-IIA was heterogeneously scattered without abnormal aggregates in the cytoplasm. We show the differential expression of mutant NMMHC-IIA and postulate that cell-specific regulation mechanisms function in MYH9 disorders.
Kunishima
Shinji
S
Department of Hemostasis and Thrombosis, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan. kunishis@nnh.hosp.go.jp
Hamaguchi
Motohiro
M
Saito
Hidehiko
H
D000328:Adult; D000595:Amino Acid Sequence; D000906:Antibodies / Q000276:immunology; D000918:Antibody Specificity; D001483:Base Sequence; D001773:Blood Cells / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006402:Hematologic Diseases / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D002479:Inclusion Bodies / Q000378:metabolism; D007223:Infant; D008297:Male; D008533:Megakaryocytes / Q000378:metabolism; D020409:Molecular Motor Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D018995:Myosin Heavy Chains / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics
D000906:Antibodies; C103814:MYH9 protein, human; D020409:Molecular Motor Proteins; D010455:Peptides; D012333:RNA, Messenger; D018995:Myosin Heavy Chains