Tag: Daniel Grimes

An investigation of novel left-right patterning genes in zebrafish

Presenter: Maisey Schering – Biochemistry, Biology

Faculty Mentor(s): Katie Fisher, Daniel Grimes

Session: (In-Person) Poster Presentation

Breaking of left-right (L-R) symmetry is a fundamental part of animal development. To facilitate this, cell to cell communication via extracellular fluid flow plays a critical role. Failure of this communication results in developmental diseases such as congenital heart disease and abnormal L-R positioning of the organs, termed heterotaxia. Understanding the mechanisms by which fluid flow signals control asymmetry is essential for understanding how to treat these diseases. In embryonic development of zebrafish, the model organism of this project, asymmetric flow in Kupffer’s vesicle (KV) breaks L-R symmetry. The flow signal results in asymmetric repression of an mRNA, dand5, triggering asymmetrical development of the emerging organs. How cells sense and transduce fluid flow, leading to dand5 repression, is not understood. My mentor in the Grimes lab, Katie Fisher, performed a literature review that resulted in 90 novel candidate genes which might regulate L-R asymmetry. These genes are all expressed at the right time and place during development to control fluid flow signaling. We are using a CRISPR/Cas9 screen to identify which of these genes are essential for L-R patterning. Several genes of interest have been identified and homozygous lines with these mutations are currently being generated. I will describe our ongoing screening efforts and early results. By completion of this project, we will know how these novel genes act to ultimately control organ asymmetry.

A Novel Zebrafish Mutant Reveals New Insight into Cilia Motility Regulation and Body Axis Formation

Presenter: Craig Samuel — Biology

Faculty Mentor(s): Daniel Grimes, Zoe Irons

Session: (In-Person) Oral Panel—Bio-Zebrafish and DNA

Motile cilia are responsible for critical functions in development, including left-right patterning and cerebrospinal fluid flow. Their motility depends on the assembly of outer dynein arms: ATPases which power ciliary beating. Defects in dynein arm function occur in Primary Ciliary Dyskinesia, a disorder affecting 1:15,000–30,000 human births. Daw1 is a cytoplasmic protein thought to be required for cilia beating by controlling import of dynein arms into cilia. Here, I use zebrafish as a model to understand Daw1 function during development and growth. I characterize daw1b1403 mutants, a new daw1 mutant line harboring a 2-amino acid deletion in a conserved region of the protein generated by CRISPR mutagenesis. Defects associated with motile cilia dysfunction in daw1b1403 mutants, including otolith abnormalities, left-right patterning defects, and abnormal body axis curvature are observed. Surprisingly, daw1b1403 mutants exhibit recovery of body curve defects later in development. Consequently, we hypothesize that Daw1 is not essential for cilia motility per se, but only for timely onset of beating over developmental timescales. Importantly, this Daw1 model of delayed cilia motility and body straightening provides an opportunity to study how early embryos can sense, or correct, shape deformations, which is an exciting and relatively unknown aspect of developmental morphogenesis. Ultimately, understanding these processes may help inform our treatments of congenital disorders.