PROJECT SUMMARY/ABSTRACT
Deletion of a region of Chromosome 22q11.2 (22qDS) encoding over 40 protein-coding genes is the most
common microdeletion syndrome (~1/2000 live births) and predisposes to multiple neurodevelopmental
disorders (NDDs). Individuals with 22qDS display microcephaly and 22qDS models suggest deficits in neural
stem and progenitor cell (NSPC) proliferation may be contribute, though the complement of genes and
mechanisms involved are not known. Six of the genes in the 22qDS deleted region encode mitochondrial
proteins and mitochondria are important regulators of neurogenesis, suggesting loss of these genes may
contribute to disturbed NSPC proliferation. Preliminary data derived from high throughput behavioral screening
of 22qDS orthologs indicates that two mitochondrial proteins (mrpl40 and prodha) encoded in the 22qDS
deleted region regulate NSPC proliferation, brain size, and behavior in zebrafish. The goal of this proposal is to
define the mechanisms through which mrpl40 and prodha govern NSPC proliferation with the hypothesis that
NSPC mitochondrial dysfunction in 22qDS may represent a convergent pathologic mechanism. To this end,
experiments will employ an innovative combination of in vivo zebrafish studies focused on individual 22qDS
genes and cortical organoid studies that model the entire 22q11.2 deletion. Aim 1 will employ cell-type specific
transgenic rescue approaches to determine in which cell types mrpl40 and prodha function to regulate brain
structure and behavior. Single cell RNA sequencing in zebrafish mutants will be used to define how
progenitor/post-mitotic cell populations are altered. Aim 2 will utilize in vivo imaging of transgenic reporters of
redox status and cell cycle in zebrafish to define redox dynamics during neurogenesis and to determine how
mrpl40 and prodha function to regulate NSPC redox status and proliferation. Aim 3 will use cortical organoid
approaches to define NSPC proliferation abnormalities caused by 22q11.2 deletion in a model of human
cortical development. The contribution of mrpl40 will then be assessed by analyzing mrpl40 mutant cortical
organoids. This proposal fits within NINDS' Strategic Plan, to understand how genes guide healthy brain
development and the basic mechanisms underlying NDDs and is expected to generate important insights into
mitochondrial regulation of neurogenesis and mechanisms underlying NSPC dysfunction in 22qDS and NDDs.
To complement his scientific background, Dr. Campbell will receive training in induced pluripotent stem cell
models, next generation sequencing approaches, and in vivo imaging. Dr. Campbell will receive mentorship
from Drs. Granato and Anderson who possess complementary expertise and are uniquely suited for this
proposal. A thoughtfully selected advisory committee will provide further scientific and career mentorship.
Together with the world-class resources and scientific community available at the University of Pennsylvania,
the proposed scientific and training objectives will create a strong foundation to establish an independent
research program focused on mitochondrial mechanisms governing brain development and underlying NDDs.
