Structural and Enzymological Evidence for an Altered Substrate Specificity in Okur-Chung Neurodevelopmental Syndrome Mutant CK2αLys198Arg

A Case of Okur-Chung Neurodevelopmental Syndrome with a Novel, de novo Variant on the CSNK2A1 Gene in a Turkish Patient

Introduction

Okur-Chung neurodevelopmental syndrome (OCNDS; #617062) has been associated with heterozygous mutations in the CSNK2A1 gene (*115440) mapped on the chromosome's 20p13 region.

Case Presentation

The analysis was performed on a 2-year-old patient who was admitted to our genetic diseases evaluation center by his family with a complaint of hypotonia. We detected a heterozygous NM_177559.3 (CSNK2A1):c.1139_1140dupGG (p.Met381GlyfsTer32) variant in the CSNK2A1 gene from a whole-exome sequence analysis.

Conclusion

The variant that we detected has not been reported in open-access databases to date, so it was evaluated as a novel likely pathogenic variant according to the ACMG-2015 criteria. No variant was detected upon segregation analysis of the patient's parents; therefore, the related variant was evaluated as de novo. In this study, we offer the first report of a pathogenic frameshift variant in the CSNK2A1 gene that has a relationship with OCNDS.

Predictive functional, statistical and structural analysis of CSNK2A1 and CSNK2B variants linked to neurodevelopmental diseases

Okur-Chung Neurodevelopmental Syndrome (OCNDS) and Poirier-Bienvenu Neurodevelopmental Syndrome (POBINDS) were recently identified as rare neurodevelopmental disorders. OCNDS and POBINDS are associated with heterozygous mutations in the CSNK2A1 and CSNK2B genes which encode CK2α, a serine/threonine protein kinase, and CK2β, a regulatory protein, respectively, which together can form a tetrameric enzyme called protein kinase CK2. A challenge in OCNDS and POBINDS is to understand the genetic basis of these diseases and the effect of the various CK2⍺ and CK2β mutations. In this study we have collected all variants available to date in CSNK2A1 and CSNK2B, and identified hotspots. We have investigated CK2⍺ and CK2β missense mutations through prediction programs which consider the evolutionary conservation, functionality and structure or these two proteins, compared these results with published experimental data on CK2α and CK2β mutants, and suggested prediction programs that could help predict changes in functionality of CK2α mutants. We also investigated the potential effect of CK2α and CK2β mutations on the 3D structure of the proteins and in their binding to each other. These results indicate that there are functional and structural consequences of mutation of CK2α and CK2β, and provide a rationale for further study of OCNDS and POBINDS-associated mutations. These data contribute to understanding the genetic and functional basis of these diseases, which is needed to identify their underlying mechanisms.