Early, nonlethal ploidy and genome size quantification using confocal microscopy in zebrafish embryos.

Area of Science:

• Developmental Biology
• Genetics
• Evolutionary Biology

Background:

• Whole genome duplication (polyploidy) drives evolutionary innovation by creating gene redundancy for novel trait development.
• Polyploid vertebrates maintain nuclear:cytoplasmic ratio, leading to larger cells and reduced cell numbers to preserve body size.
• Teleosts, including zebrafish, offer facile ploidy manipulation, making them ideal models for polyploidy research.

Purpose of the Study:

• To establish a novel, non-lethal method for assessing genome size and ploidy in zebrafish embryos.
• To enable the study of polyploidy's effects on development and physiology by distinguishing between diploid and triploid individuals.
• To provide a reliable technique for researchers using zebrafish as a model organism for polyploidy studies.

Main Methods:

• Utilized confocal microscopy to measure genome size and determine ploidy in transgenic zebrafish expressing fluorescent histones at 48 hours post-fertilization (hpf).
• Employed volumetric analysis of myofiber nuclei via open-source software to differentiate between diploid and triploid embryos.
• Validated the ploidy determination method by comparing heart rates of confirmed diploid and triploid embryos at 54 hpf.

Main Results:

• A novel, non-lethal technique was successfully developed to accurately determine ploidy in zebrafish embryos.
• Volumetric analysis of myofiber nuclei reliably distinguished between diploid and triploid zebrafish.
• The method allows for the selection of specific ploidy embryos for subsequent physiological studies, demonstrated by heart rate comparison.

Conclusions:

• This confocal microscopy and volumetric analysis technique provides a robust, non-lethal means to identify ploidy in zebrafish.
• The method facilitates research into the developmental and physiological consequences of polyploidy in a key biomedical model.
• Future studies can now effectively compare diploid and triploid zebrafish to understand the functional impacts of altered cell size and number.