Proteomics characterization of CENP-B epitope in Moroccan scleroderma patients with anti-centromere autoantibodies

BACKGROUND

Anti-centromere auto-antibodies (ACA) have been described as a marker in Systemic sclerosis (SSc) disease. CENP-B is the major centromere auto-antigen recognized by SSc patients with positive ACA. Our aim was to characterize the major epitope involved in the anti-CENP-B immune response of Moroccan SSc patients.

PATIENTS AND METHOD

For identification of SSc biomarkers, 80 sera from patients with SSc and systemic lupus erythematosus (SLE) were screened by indirect immunofluorescence test (IIF) to assess the presence of ANA reactivity. Immunoblotting analysis was performed for 11 sera with positive ACA using the N-terminal and C-terminal region of CENP-B protein as antigens.

RESULTS

29 out of 30 (96, 66 %) patients with SSc had positive ANA. 11 out of 30 (36, 67 %) patients were ACA positive and 6 of them produced auto-antibodies against Nt-CENPB antigen. Two of these 6 Nt-CENPB positive sera produced also other auto-antibodies associated to primary biliary cirrhosis. None of all sera tested showed reactivity against Ct-CENPB.

CONCLUSION

Our data showed, for the first time in Morocco, that the Nt-CENPB contains a major epitope for Moroccan SSc patients. These findings could provide additional information that would contribute to improving the diagnosis and management of these patients.

Anti-CENPI autoantibodies in scleroderma patients with features of autoimmune liver diseases

BACKGROUND

Anticentromere autoantibodies have been reported to be associated with scleroderma and serve as a marker in different rheumatic diseases in humans. Major centromere autoantigens described so far include constitutive kinetochore proteins such as CENPA, CENPB, CENPC and CENPH and facultative proteins such as CENPE, CENPF and INCENP. We examined the inner kinetochore component CENPI as a new putative centromere autoantigen in scleroderma patients.

METHODS

To test for the presence of CENPI centromere autoantibodies, 72 sera from patients with systemic lupus erythematosus and systemic sclerosis were assayed by immunofluorescence and further tested by immunoblots with an Nt-CENPI recombinant protein.

RESULTS

8 out of 31 (25.8%) patients diagnosed of scleroderma or Undifferentiated Connective Tissue Disease (UCTD) produced anti-CENPI autoantibodies. Epitopes were demonstrated to be located mainly but not exclusively in the N-terminal domain of the human CENPI protein. Five of the 8 (62.5%) CENPI positive sera also had other autoantibodies related to primary biliary cirrhosis. Further, two patients (25%) with anti-CENPI autoantibodies had concurrent diagnosis of primary biliary cirrhosis.

CONCLUSIONS

This study demonstrates that CENPI, a centromere protein that localizes to the inner kinetochore structure, is a human autoantigen. The significance of anti-CENPI autoantibodies could be relevant in scleroderma patients as a marker for concurrent autoimmune liver disease.

CENPA a genomic marker for centromere activity and human diseases

Inheritance of genetic material requires that chromosomes segregate faithfully during cell division. Failure in this process can drive to aneuploidy phenomenon. Kinetochores are unique centromere macromolecular protein structures that attach chromosomes to the spindle for a proper movement and segregation. A unique type of nucleosomes of centromeric chromatin provides the base for kinetochore formation. A specific histone H3 variant, CENPA, replaces conventional histone H3 and together with centromere-specific-DNA-binding factors directs the assembly of active kinetochores. Recent studies on CENPA nucleosomal structure, epigenetic inheritance of centromeric chromatin and transcription of pericentric heterochromatin provide new clues to our understanding of centromere structure and function. This review highlights the role and dynamics of CENPA assembly into centromeres and the potential contribution of this kinetochore protein to autoimmune and cancer diseases in humans.