A novel thrombocytopenia-4-causing CYCS gene variant decreases caspase activity: Three-generation study

Area of Science:

• Genetics
• Molecular Biology
• Hematology

Background:

• The CYCS gene is crucial for mitochondrial function and is highly conserved.
• Pathogenic variants in CYCS can lead to thrombocytopenia-4 (THC4), a bleeding disorder.
• Understanding CYCS variant effects is vital for diagnosing and treating inherited thrombocytopenia.

Purpose of the Study:

• To identify and characterize a novel CYCS gene variant associated with thrombocytopenia in a Czech family.
• To investigate the molecular mechanisms by which this CYCS variant affects platelet production and function.
• To explore the potential role of caspase dysregulation in CYCS-related thrombocytopenia.

Main Methods:

• Segregation analysis of the novel CYCS variant (c.59C>T) in a three-generation family.
• CRISPR/Cas9 gene editing to introduce the variant into the MEG-01 megakaryoblast cell line.
• Comprehensive analysis of cellular functions including adhesion, respiration, protein expression, and caspase activity.

Main Results:

• The novel CYCS variant (p.(Thr20Ile)) segregates with dominant thrombocytopenia (THC4) with normal platelet size/morphology and progressive decline across generations.
• The variant reduces CYCS expression, enhances mitochondrial respiration, and increases CD9 cell surface antigen expression.
• The variant significantly inhibits caspase activation, a novel finding potentially linked to thrombopoiesis dysregulation.

Conclusions:

• A new CYCS variant causes inherited thrombocytopenia-4 with unique molecular consequences.
• Dysregulated caspase activity due to the CYCS variant may contribute to the pathogenesis of thrombocytopenia.
• These findings advance the understanding of inherited thrombocytopenia and may inform future therapeutic strategies.