Molecular Diversity and Associated Phenotypic Spectrum of Germline CBL Mutations

Area of Science:

• Genetics
• Molecular Biology
• Developmental Biology

Background:

• Noonan syndrome (NS) is a common developmental disorder linked to the RAS-MAPK pathway.
• Casitas B-lineage lymphoma proto-oncogene (CBL), an E3-ubiquitin ligase, has been identified as a gene associated with NS-related conditions.
• CBL acts as a tumor suppressor in myeloid malignancies.

Purpose of the Study:

• To investigate the spectrum of germline CBL mutations and their associated phenotypes.
• To identify novel CBL variants and understand their functional impact.
• To establish genotype-phenotype correlations in individuals with CBL mutations.

Main Methods:

• Germline CBL mutation scanning in 349 subjects with NS-like features and no mutations in known NS genes.
• Identification and characterization of pathogenic CBL variants, including splice-site, deletion, missense, and nonsense mutations.
• Genotype-phenotype correlation analysis using available patient data.

Main Results:

• Five pathogenic germline CBL variants were identified, including mutations affecting the RING domain and a novel nonsense mutation.
• These mutations lead to a variable phenotype with frequent neurological features, predisposition to juvenile myelomonocytic leukemia, and less common cardiac defects, growth reduction, and cryptorchidism.
• CBLB and CBLC family members were excluded as major contributors to NS and related disorders.

Conclusions:

• Germline CBL mutations are a cause of a Noonan syndrome-like disorder with a distinct phenotype.
• Specific CBL mutations can alter protein function, impacting RAS signaling.
• The study clarifies the role of CBL in developmental disorders and cancer predisposition.