Image analysis of neutrophil nuclear morphology: Learning about phenotypic range and its reliable analysis from patients with pelger‐Huët‐anomaly and treated with colchicine

Abstract

The nuclear morphology of neutrophils depends on different endogenous and exogenous factors, which can lead to hypo- or hypersegmentation of the normally 2-4 segmented nucleus. Hyposegmentation can be due to mutations in the LBR-gene (Pelger-Huët-Anomaly) or can be induced, for example, by colchicine treatment. The range of this phenotypic variation is known as "norm of reaction," which can be of major relevance for clinical diagnosis and therapeutic intervention. In this project, we studied the norm of reaction in 26 subjects with 0-3 wild type LBR alleles. In addition, the phenotypic variation was analyzed in 3 patients with Familial Mediterranean Fever (FMF), before and after colchicine treatment. We measured the phenotype nuclear segmentation of neutrophils based on two conventional qualitative methods, the "rule of threads" and the "rule of thirds." In addition, we tested a morphometric quantitative approach, the "circularity index." The circularity index was superior in cases with hyposegmentation; the rule of thirds with respect to hypersegmentation. Approximately 65% of the observed phenotypic variance was explainable by the number of LBR wild type alleles. The gene-dosage effect followed a non-additive, hysteresis-like characteristic with lower and upper plateaus. Colchicine treatment had a clear, although minor phenotypic effect compared to the number of LBR wild type genes or the mutation type. Thus, the nuclear morphology of granulocytes and its norm of reaction can be regarded as an excellent model both for detailing the interplay between endogenous and exogenous factors and for clinical diagnostic purposes. © 2016 International Clinical Cytometry Society.

Nuclear Morphological Remodeling in Human Granulocytes Is Linked to Prenylation Independently from Cytoskeleton

“…While downregulation of the cholesterol biosynthesis might be linked to immune system specification and terminal differentiation [50][51][52], several arguments prompted a more detailed investigation of this pathway. Firstly, mutations of one of its key enzymes (laminB-receptor, LBR) cause Pelger-Huët anomaly [53], a condition in which haploinsufficiency results in hypolobulated granulocytic nuclei [31], while excess gene copies promote hyperlobulation [30,32]. Secondly, pathways involved in lipid metabolism play preeminent roles in membrane bending and nuclear invagination genesis, with phosphatidylcholine-related enzyme CCTα being essential for their organization [54][55][56].…”

“…In vivo, differentiation is uncoupled from nuclear remodeling, as shown by functionally mature granulocytes displaying round or non-lobulated nuclei upon mutations in laminB-receptor (LBR) gene [30][31][32]. Given this concurrent but not necessarily causative relationship, we temporally profile transcriptomic changes in differentiating granulocytes and identify a metabolic pathway involving the enzymatic activity of LBR as temporally concurrent with nuclear remodeling.…”

Roles of the nucleus in leukocyte migration

“…Loss of LBR causes the loss of polymorphonuclear phenotypes in granulocytes, 76,80,81 and hyperlobulation is associated with an increased copy number of the LBR gene (Figure 3(C)). 82 Defective LBR mRNA splicing and abnormal LBR protein folding also lead to PHA 83,84 . Down‐regulation of lamin A/C is necessary because overexpression of either lamin isoform greatly reduces the number of multilobed nuclei 54 …”

Issue Highlights ‐ November 2017 (92:B6)

“…Schnipper, et al use an algorithm to measure the nuclear morphology of granulocytes from hypo‐ to hyper‐segmentation. This is clinically useful regarding colchicine therapy or the determination of the Pelger‐Huet‐Anomaly.…”