Detecting Chromosome Condensation Defects in Gulf War Illness Patients

Abstract

Background: Gulf War Illness (GWI) impacts 25-30% of gulf war veterans. Due to its heterogeneity in both etiology and symptoms, it has been challenging to establish the commonly accepted case definition for GWI. Equally challenging are the understanding of the general mechanism of GWI and the development of biomarkers useful for its clinical diagnosis and treatment.

Objective: We have observed that chromosome condensation defects can be detected in GWI patients. To document this phenomenon in GWI, we aim to describe and compare different types of chromosomal condensation defects in GWI patients, if possible. Since chromosomal condensation represents an important step of ensuring genome integrity, condensation defects could be used as a potential biomarker of GWI.

Methods: Lymphocytes from GWI patients have been used for short term cell culture followed by chromosome slide preparation. Both Giemsa staining and multiple color spectral karyotyping (SKY) were applied to study chromosome aberrations, focusing on different types of condensation defects.

Results: At least three subtypes of Defective Mitotic Figures (DMFs) were observed. Some individuals displayed elevated frequencies of DMFs. Another type of condensation defect identified as sticky chromosomes were also observed.

Conclusion: Various types of condensation defects have been observed in GWI patients. It is rather surprising that some GWI patients exhibited a high level of chromosomal condensation defects. Previously, the elevated frequency of DMFs was only observed in cancer patients. Since chromosome condensation can be linked to other types of chromosome aberrations, as well as cellular stress conditions, the detailed mechanism and clinical impact should be further studied, especially with increased sample size.

Keywords: Chromosome aberrations; Defective Mitotic Figures (DMFs); Fuzzy inheritance; Genome heterogeneity; Genome instability; Gulf war illness (GWI); Sticky chromosomes; Stress.

Fig. (1)

Examples of DMFs detected from GWI patients. A-C) Type 1 DMFs with the typical polarizing shape where the condensed chromosomes group at one end and the un-condensed chromatin in the opposite direction (Giemsa staining). In C) an arrow indicates a less condensed chromosome. D-E) Type 2 DMFs with more random distribution of de-condensed chromosomes. In D), there is a mixture of DMFs and sticky chromosomes (Giemsa staining). In E), there is a mixture of condensed and de-condensed chromosomes (DAPI staining). F) Type 3 DMF, a few chromosomes display diffused morphology among most seemingly normal chromosomes (Giemsa staining). Note that the morphology of defused chromosomes differs from chromosome fragmentation. G) A few isolated de-condensed chromosomes (Giemsa staining).

Fig. (2)

Images of sticky chromosomes. A) a portion of the mitotic figure displays sticky chromosomes where multiple sticky chromosomes form a cluster (as indicated by the arrows) (Gimesa staning); B) a comparison between non-sticky chromosomes (top right) and sticky chromosomes (indicated by an arrow), which is different from 2A as the sticky chromosome cluster likely belongs to a different mitotic figure; C-D) sticky chromosomes are detected across the entire mitotic figure. In picture D, many sticky chromosomes have fused together.

Fig. (3)

Reversed DAPI (A) and SKY image (B) of sticky chromosomes, normal chromosomes, and interphase nuclei. Many sticky chromosomes form a chromosome bundle. The reverse-DAPI image provides less detailed information, while the SKY image shows the chromosomes sticking together (this is not a bundle of de-condensed chromatin fibers), as the defined color domain is visible, which is different from the interphase signals, revealing the condensed chromosomal status.