Granulocytic nuclear differentiation of lamin B receptor-deficient mouse EPRO cells.
OBJECTIVE
Lamin B receptor (LBR) is an integral protein of the inner nuclear membrane. Recent studies have demonstrated that genetic deficiency of LBR during granulopoiesis results in hypolobulation of the mature neutrophil nucleus, as observed in human Pelger-Huët anomaly and mouse ichthyosis (ic). In this study, we utilized differentiated early promyelocytes (EPRO cells) that were derived from the bone marrow of homozygous and heterozygous ichthyosis mice to examine changes to the expression of nuclear envelope proteins and heterochromatin structure that result from deficient LBR expression.


METHODS
Wild-type (+/+), heterozygous (+/ic), and homozygous (ic/ic) granulocytic forms of EPRO cells were analyzed for the expression of multiple lamins and inner nuclear envelope proteins by immunostaining and immunoblotting techniques. The heterochromatin architecture was also examined by immunostaining for histone lysine methylation.


RESULTS
Wild-type (+/+) and heterozygous (+/ic) granulocytic forms revealed ring-shaped nuclei and contained LBR within the nuclear envelope; ic/ic granulocytes exhibited smaller ovoid nuclei devoid of LBR. The pericentric heterochromatin of undifferentiated and granulocytic ic/ic cells was condensed into larger spots and shifted away from the nuclear envelope, compared to +/+ and +/ic cell forms. Lamin A/C, which is normally not present in mature granulocytes, was significantly elevated in LBR-deficient EPRO cells.


CONCLUSIONS
Our observations suggest roles for LBR during granulopoiesis, which can involve augmenting nuclear membrane growth, facilitating compartmentalization of heterochromatin, and promoting downregulation of lamin A/C expression.
Zwerger
Monika
M
German Cancer Research Center, Heidelberg, Germany.
Herrmann
Harald
H
Gaines
Peter
P
Olins
Ada L
AL
Olins
Donald E
DE
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D002478:Cells, Cultured; D018385:Centrosome / Q000648:ultrastructure; D017353:Gene Deletion; D006098:Granulocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D006570:Heterochromatin / Q000378:metabolism; D006579:Heterozygote; D006720:Homozygote; D007057:Ichthyosis / Q000235:genetics*; D051379:Mice; D009685:Nuclear Envelope / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics*; D014212:Tretinoin / Q000494:pharmacology; D000097682:Lamin B Receptor
D015415:Biomarkers; D006570:Heterochromatin; D018160:Receptors, Cytoplasmic and Nuclear; D014212:Tretinoin; D000097682:Lamin B Receptor