November 16, 2022
1:30 pm / 3:00 pm
TITLE: Identification of Wnt Ligands Regulating Planar Cell Polarity in the Developing Mouse Cochlea
Ippei Kishimoto (1)
Erin Su (1)
Alan G. Cheng (1)
- Department of Otolaryngology, Head & Neck Surgery
DATE: Wednesday, 16 November 2022
TIME: 1:30–3:00 PM
LOCATION: Conference Room X303, Medical School Office Building, 1265 Welch Road, Stanford, CA
The Data Studio Workshop brings together a biomedical investigator with a group of experts for an in-depth session to solicit advice about statistical and study design issues that arise while planning or conducting a research project. This week, the investigator(s) will discuss the following project with the group.
A vital part of the mammalian inner ear is the cochlea, a spiral-shaped sensory organ with hair cell (HC) bundles that detect sound vibrations in the cochlear fluid. Hearing function critically depends upon the unidirectional polarization of HCs and their stereocilia. The PCP pathway organizes cells in tissue planes. Hair cells are precisely oriented with hair bundles aligned radially, serving as a prime example where proper development requires the PCP pathway. We previously showed that PCP during cochlear development, including, cochlear extension, hair cell orientation and core PCP protein polarization, is regulated by Wnt secretion from the embryonic cochlear epithelium. However, the specific Wnt ligands among 19 Wnts contributing to cochlear PCP are still unknown.
HYPOTHESIS & AIM
The aim of the study is to elucidate the role of individual Wnt members in the establishment of cochlear PCP, and then we put these hypotheses:
(1) The establishment of cochlear PCP requires specific Wnt ligands
(2) Epithelia- and mesenchyme-derived Wnt ligands are both required for cochlear PCP establishment
To test these hypotheses, we generated the conditional knockout (cKO) mice for specific target Wnts (Wnt4, Wnt5a, Wnt7a, Wnt7b etc.), in which the expression of the target Wnt is deleted in cochlear epithelium or periotic mesenchyme. Then, we look at three readouts for cochlear PCP (cochlear extension, hair cell orientation and core PCP protein polarization) to see if which Wnt contributes to the establishment of cochlear PCP.
What we’d like to ask for advice about is the second readout, hair cell orientation. What we do to see if these cKO mouse have PCP abnormality in hair cell orientation is to measure the orientation of each hair cell (degrees; from -180° to 180°) relative to a specific reference line and to compare them between control (WT) and experimental (cKO) groups. Usually in our datasets, each of control and experimental groups consists of 3 to 5 mice, and each mouse has about 20 to 40 values (such as 23.45°, -4.543°, 9.212°, 11.098°, -9.101°……).
We’d like to see if there is significant difference in the average direction or the variation of angles between control and experimental groups. What we already tried to compare the variation of angles, is to simply compare standard deviation (SD) of the angles between both groups. For example, a control group has 5 mice so 5 SDs, and an experimental group has 4 mice so 4 SDs, and then we compare both groups with unpaired t-test, such as (8.44, 6.86, 6.50, 5,35, and 8.34) VS (6.79, 6.62, 7.55, and 6.94). However, this method did not seem to detect small differences and could not reproduce the results as reported in the past.
To compare the average direction or the variation of angles between control and experimental groups, what statistical comparison methods are appropriate?