Zebrafish cdc6 hypomorphic mutation causes Meier-Gorlin syndrome-like phenotype.

Area of Science:

• Genetics
• Developmental Biology
• Molecular Biology

Background:

• Meier-Gorlin syndrome (MGS) is a human genetic disorder linked to mutations in pre-replicative complex (preRC) genes, including CDC6.
• Vertebrate models for MGS are currently lacking, hindering research into the syndrome's mechanisms and potential treatments.

Purpose of the Study:

• To generate and characterize zebrafish models of MGS by creating cdc6 mutant lines.
• To investigate the in vivo function of Cdc6 in vertebrate development and its role in MGS pathogenesis.

Main Methods:

• Zebrafish were subjected to N-ethyl-N-nitrosourea mutagenesis and Cas9 knockout to generate cdc6 mutant lines.
• Phenotypic analysis of loss-of-function and hypomorphic cdc6 mutants was performed, including assessment of embryonic lethality, cell cycle progression, apoptosis, growth, and reproductive capacity.
• Human CDC6 mutations were modeled by overexpression in zebrafish mutants to assess functional complementation.

Main Results:

• Loss-of-function cdc6 mutants exhibited embryonic lethality due to S-phase arrest and apoptosis.
• A hypomorphic cdc6 mutant (cdc6tsu21cd) displayed growth retardation, reduced adult size, and reproductive defects, closely resembling human MGS.
• Overexpression of a human CDC6 mutation (CDC6(T323R)) partially rescued the cell death phenotype in zebrafish mutants, suggesting it is a hypomorphic mutation.

Conclusions:

• Zebrafish cdc6 mutants provide a valuable vertebrate model for studying MGS.
• The cdc6tsu21cd mutant fish exhibit phenotypes relevant to MGS, including growth and reproductive abnormalities.
• This model can facilitate further investigation into MGS tissue defects and the development of therapeutic strategies.