Distinct Lineage Origins and Signaling Requirements for Enteric Nervous System Development

Core Concepts

The enteric nervous system (ENS) arises from distinct neural crest and placodal cell lineages, which utilize endothelin and GDNF signaling pathways in a lineage-specific manner to support their migration and differentiation.

Abstract

The study investigates the distinct contributions of neural crest (Wnt1Cre lineage) and placodal (Pax2Cre lineage) cell populations to the development of the enteric nervous system (ENS). It demonstrates that these two lineages have different molecular requirements for their migration and differentiation, specifically in terms of the endothelin (Edn3-Ednrb) and GDNF (GDNF-Ret) signaling pathways.
Key findings:

Both Wnt1Cre and Pax2Cre lineages contribute to the ENS, but they give rise to distinct neuronal subtypes. Pax2Cre-derived cells preferentially differentiate into CGRP+ mechanosensory neurons, while Wnt1Cre-derived cells mainly generate NOS+ inhibitory motor neurons.
Edn3-Ednrb signaling is required in both lineages for their migration and colonization of the hindgut. Conditional Ednrb mutation in either Wnt1Cre or Pax2Cre lineages results in Hirschsprung's disease-like phenotypes.
GDNF-Ret signaling is also essential for ENS progenitor migration, but its requirement intersects with Edn3-Ednrb signaling differently in the two lineages. Ret deficiency in the Pax2Cre lineage impacts the migration and differentiation of both Pax2Cre-derived and Wnt1Cre-derived ENS progenitors.
In vitro explant assays show that GDNF promotes the outgrowth and differentiation of ENS progenitors, but this response is impaired in the Pax2Cre/Ret mutant background, indicating a cell-autonomous requirement for Ret in the Pax2Cre lineage.

These findings demonstrate that the ENS arises from distinct neural crest and placodal lineages, which utilize endothelin and GDNF signaling pathways in a lineage-specific manner to support their migration and differentiation during development.

Stats

Pax2Cre/Ednrb mutant mice exhibit growth retardation, reduced weight gain, and near complete abrogation of defecation, similar to global Ednrb and Wnt1Cre/Ednrb mutants.
In E12.5 Pax2Cre/Ednrb and Wnt1Cre/Ednrb mutant embryos, lineage-labeled cells fail to advance beyond the cecum, resulting in an absence of lineage-labeled cells in the distal colon of postnatal mice.
In P9 distal colons, over 90% of CGRP+ mechanosensory neurons are derived from the Pax2Cre lineage, while the majority of NOS+ inhibitory motor neurons are from the Wnt1Cre lineage.
In Pax2Cre/Ednrb mutants, there is a profound reduction of CGRP+ axons projecting towards the enteric lumen, while NOS+ axons in the circular muscle are present normally. The opposite is true in Wnt1Cre/Ednrb mutants.
In E10.5 Pax2Cre/Ret mutant embryos, the total number of countable ENS progenitor cells (Pax2Cre-derived and non-Pax2Cre) is reduced by half compared to controls.

Quotes

"Pax2Cre-derived cells preferentially give rise to CGRP+ mechanosensory neurons of the distal colon."
"Wnt1Cre-derived cells mainly generate NOS+ inhibitory motor neurons."
"GDNF-Ret signaling is also essential for ENS progenitor migration, but its requirement intersects with Edn3-Ednrb signaling differently in the two lineages."

Key Insights Distilled From

Lineage-specific intersection of endothelin and GDNF signaling in enteric nervous system development

by Poltavski,D.... at www.biorxiv.org 02-14-2024

https://www.biorxiv.org/content/10.1101/2024.02.13.580135v1

Deeper Inquiries

What are the potential implications of the lineage-specific differences in ENS development for understanding and treating enteric nervous system disorders

The lineage-specific differences in ENS development have significant implications for understanding and treating enteric nervous system disorders. By identifying distinct sublineages within the ENS that utilize different signaling pathways, researchers can gain insights into the specific mechanisms that govern the migration and differentiation of enteric progenitor cells. This knowledge can help in the development of targeted therapies for ENS disorders such as Hirschsprung disease, where mutations in genes like Edn3, Ednrb, Ret, and GDNF lead to colonic aganglionosis. Understanding how these signaling pathways intersect and diverge in different ENS sublineages can provide valuable information for developing precision medicine approaches tailored to the specific genetic defects present in individual patients. Additionally, insights into the lineage-specific contributions to ENS development can aid in the identification of novel therapeutic targets and the design of regenerative strategies to restore ENS function in patients with congenital or acquired ENS disorders.

How might the distinct signaling requirements of the Pax2Cre and Wnt1Cre lineages be leveraged for regenerative approaches to restore ENS function

The distinct signaling requirements of the Pax2Cre and Wnt1Cre lineages in ENS development can be leveraged for regenerative approaches aimed at restoring ENS function. For example, the specific response of Pax2Cre-derived cells to GDNF and the requirement for Ret signaling in this lineage suggest that targeting the GDNF-Ret pathway could be a promising strategy for promoting the migration and colonization of Pax2Cre-derived enteric progenitor cells in regenerative therapies. By understanding the unique signaling dependencies of each lineage, researchers can design targeted interventions that stimulate the appropriate signaling pathways to promote the differentiation and integration of ENS progenitor cells into the gastrointestinal tract. This knowledge can inform the development of cell-based therapies, gene therapies, or pharmacological interventions that aim to restore ENS function in patients with ENS disorders.

Are there any other developmental processes or tissue types where the Pax2Cre and Wnt1Cre lineages exhibit similar lineage-specific utilization of signaling pathways

The Pax2Cre and Wnt1Cre lineages exhibit similar lineage-specific utilization of signaling pathways in other developmental processes and tissue types. For example, in the inner ear, these lineages contribute to distinct components of the auditory system, with Pax2Cre labeling placode-derived cells and Wnt1Cre labeling neural crest-derived cells. Similarly, in the ENS, Pax2Cre labels a specific sublineage of enteric progenitor cells that give rise to mechanosensory neurons, while Wnt1Cre labels a different sublineage that contributes to motor neurons and interneurons. This pattern of distinct lineage-specific contributions to different cell types within a tissue or organ is a common theme in developmental biology, where lineage-specific markers like Pax2Cre and Wnt1Cre can be used to trace the origins of specific cell populations and understand their unique developmental trajectories and signaling requirements.