PROJECT SUMMARY/ABSTRACT
The majority of congenital hearing loss cases are sensorineural (SNHL), and at least half are associated with
genetic defects. Unfortunately, regenerative medicine and gene therapy for inner ear diseases have generally
not been realized in human patients due to the inability to ethically experiment on large numbers of human
embryos in a scientifically rigorous manner. This also means that key knowledge gaps exist in the overall
understanding of the early development of human sensory organs. In the case of the inner ear, it is known that
proper cell fate commitment to the otic placode is essential for inner ear formation. Both sensory epithelia, where
hair cells are located, and the vestibulocochlear nerve are derived from the otic vesicle, which is invaginated
from the otic placode; defects in hair cells and/or the vestibulocochlear nerve result in SNHL. It is difficult to study
early otic development, specifically during the induction and patterning of the pre-placodal ectodermal (PPE),
where otic placodes are derived from, in mammalian embryos (not to mention human embryos). This study aims
to 1) examine the role of WNT signaling pathways in early otic development, with a focus on the PPE, and 2)
determine how cell fate decisions in the PPE culminate in the origin of the otic lineage in human inner ear
organoids. In Aim 1, the effects of WNT signaling on otic development will be examined, with the goal of
identifying the optimal level of WNT that maximizes inner ear organoid induction. Single-cell RNA sequencing
(scRNA-seq) analyses in the human inner ear organoid system will reveal the early otic lineage progression and
mechanisms underlying the processes mediated by WNT. In Aim 2, spatial gene expression profiles of organoids
treated with the optimal level of WNT modulation will be created. Upon integrating these spatial data with the
temporal scRNA-seq data from Aim 1, a cell atlas of the early otic lineage in human inner ear organoids will be
established. These spatio-temporal transcriptomic data will then be used to create a genetic blueprint for early
human otic development, with a focus on characterizing the gene regulatory networks that are critical to cell fate
commitments underlying proper cranial sensory organ development. Such data will 1) advance human
developmental biology, 2) generate a molecular database for understanding congenital disorders associated
with ectodermal derivatives (including the inner ear), and 3) progress regenerative medicine and gene therapy
for inner ear diseases.
