# Specification and maintenance of quiescent progenitor cells set aside for the biphasic life cycle of an invertebrate chordate

> **NIH NIH R01** · GEORGIA INSTITUTE OF TECHNOLOGY · 2024 · $323,086

## Abstract

PROJECT SUMMARY/ABSTRACT
The objective of this proposal is to characterize the molecular mechanisms that specify, maintain, and
protect a discrete compartment of pre-patterned but quiescent and undifferentiated progenitor cells
(termed the “Neck”) in the tunicate Ciona. Tunicates like Ciona are the invertebrates most closely
related to vertebrates, and possess a unique biphasic life cycle alternating between a short-lived,
motile larva and a sessile adult. During metamorphosis, a mass wave of programmed cell death
eliminates most differentiated larval cells while sparing set-aside undifferentiated adult progenitor cells
that go on to form the majority of adult cell types and structures. Despite this heterochrony in
differentiation and the complete remodeling of the post-metamorphic adult, the larval and adult body
plans are contiguous and simultaneously patterned during embryonic development.
This peculiar arrangement offers a unique opportunity to study how discrete stem cell compartments
can be set aside and protected for later developmental potential in spite of the differentiation and cell
death around them. The central hypothesis is that the stereotyped specification, maintenance, and
survival of quiescent progenitor cells of the Neck are controlled by precise developmental regulation of
genes encoding rate-limiting components of diverse biochemical pathways. The rationale underlying
the proposed research is that, by exploiting the genomic and cellular simplicity of Ciona and their
radical yet naturally stereotyped transition from a motile larval body plan to a sessile adult one, we can
understand tissue remodeling and cellular turnover in much greater spatial and temporal detail.
The central hypothesis will be tested by pursuing three specific aims: 1) We will test whether Pax2/5/8
is required for establishing the Neck as a discrete compartment of adult progenitor cells. 2) We will
test the roles of FGF and Hedgehog signaling in maintaining Neck cells as a quiescent population of
undifferentiated cells. 3) We will test whether the survival of Neck cells during the wave of apoptosis
that occurs in metamorphosis requires the anti-apoptotic effects of Nitric oxide signaling and a unique
class of metalloproteins that bind vanadium, a heavy metal that has been observed to accumulate in
tunicate cells but without a known biological function. These aims will be pursued using an innovative
approach that combines cell lineage-specific CRISPR/Cas9-based somatic gene knockouts with next-
generation sequencing, in vivo fluorescence microscopy and in vitro biochemical assays. The
expected outcomes of the proposed work would be to 1) reveal conserved biological mechanisms that
might be shared with humans, and/or 2) identify highly divergent proteins and pathways that could
nonetheless be harnessed for novel therapeutic tools to treat human disease and injury.

## Key facts

- **NIH application ID:** 10877181
- **Project number:** 5R01GM143326-04
- **Recipient organization:** GEORGIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** Alberto Stolfi
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $323,086
- **Award type:** 5
- **Project period:** 2021-07-01 → 2025-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10877181

## Citation

> US National Institutes of Health, RePORTER application 10877181, Specification and maintenance of quiescent progenitor cells set aside for the biphasic life cycle of an invertebrate chordate (5R01GM143326-04). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10877181. Licensed CC0.

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