Role of maternal mRNA degradation in whole-body cellular phenotypes caused by DNA polymerase α deficiency
Alex Lin
Georgia Thomas
Khai C. Ang
Damian B. van Rossum
Victor A. Canfield
Keith C. Cheng
10.6084/m9.figshare.12145740.v1
https://tagc2020.figshare.com/articles/poster/Role_of_maternal_mRNA_degradation_in_whole-body_cellular_phenotypes_caused_by_DNA_polymerase_deficiency/12145740
<p>A histology-based zebrafish
forward genetic screen for mutations causing cytological abnormalities yielded
a mutant, <i>huli hutu </i>(<i>hht</i>), whose pleiotropic phenotype includes
atypical nuclei in gastrointestinal cells and nuclear fragmentation in the retina
and central nervous system. We have used a new, 3D form of histology based on
micro-CT, X-ray histotomography, to reveal diminished heart volume and shape,
and dysplastic cartilage and skin. We were also able to definitively establish the
absence of a swim bladder and pneumatic duct, which is challenging to determine
usig histology. Cell death shown by karyorrhexis was associated with DNA damage
identified by ɤ-H2AX stainng in the brain, eyes, and spinal cord. These
phenotypes were caused by a frameshift-based premature stop codon at the 38<sup>th</sup>
amino acid position of the 600-amino acid Pola2 protein, or B subunit of DNA
polymerase α (Pol α). An extended 120-168 hpf survival of the <i>hht </i>fish stands in striking contrast to
the immediate cell cycle arrest of the corresponding mutants in yeast and <i>Arabidopsis. </i>We found that the prolonged
lifespan of these mutants can be explained by the presence of wild-type
maternal <i>pola2 </i>mRNA in the fertilized
embryos. The gradual disappearance of wild-type mRNA in homozygous mutant
embryos appears to cause diminished DNA synthesis, increased DNA damage, cell
death, and tissue-dependent cytological deformities. The breadth of
cytological, tissue, and organ phenotypes of <i>hht </i>mutants can be used as a model for developing computational
tools for quantitative 3D characterization of pleiotropy, including cytological
and tissue phenotypes across organ systems.</p>
2020-04-20 23:14:48
DNA Polymerase Alpha
Cell Death
DNA damage
Nuclear Atypia
Nuclear Fragmentation
Maternal RNA
Pleiotropy
Genetics